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Length regulation.
Axons vary largely in length from a few micrometers up to meters in some animals. This emphasizes that there must be a cellular length regulation mechanism allowing the neurons both to sense the length of their axons and to control their growth accordingly. It was discovered that motor proteins play an important role in regulating the length of axons. Based on this observation, researchers developed an explicit model for axonal growth describing how motor proteins could affect the axon length on the molecular level. These studies suggest that motor proteins carry signaling molecules from the soma to the growth cone and vice versa whose concentration oscillates in time with a length-dependent frequency.
Classification.
The axons of neurons in the human peripheral nervous system can be classified based on their physical features and signal conduction properties. Axons were known to have different thicknesses (from 0.1 to 20 μm) and these differences were thought to relate to the speed at which an action potential could travel along the axonits "conductance velocity". Erlanger and Gasser proved this hypothesis, and identified several types of nerve fiber, establishing a relationship between the diameter of an axon and its nerve conduction velocity. They published their findings in 1941 giving the first classification of axons.
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Axons are classified in two systems. The first one introduced by Erlanger and Gasser, grouped the fibers into three main groups using the letters A, B, and C. These groups, group A, group B, and group C include both the sensory fibers (afferents) and the motor fibers (efferents). The first group A, was subdivided into alpha, beta, gamma, and delta fibersAα, Aβ, Aγ, and Aδ. The motor neurons of the different motor fibers, were the lower motor neuronsalpha motor neuron, beta motor neuron, and gamma motor neuron having the Aα, Aβ, and Aγ nerve fibers, respectively.
Later findings by other researchers identified two groups of Aa fibers that were sensory fibers. These were then introduced into a system (Lloyd classification) that only included sensory fibers (though some of these were mixed nerves and were also motor fibers). This system refers to the sensory groups as Types and uses Roman numerals: Type Ia, Type Ib, Type II, Type III, and Type IV.
Motor.
Lower motor neurons have two kind of fibers:
Different sensory receptors are innervated by different types of nerve fibers. Proprioceptors are innervated by type Ia, Ib and II sensory fibers, mechanoreceptors by type II and III sensory fibers and nociceptors and thermoreceptors by type III and IV sensory fibers.
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Autonomic.
The autonomic nervous system has two kinds of peripheral fibers:
Clinical significance.
In order of degree of severity, injury to a nerve in the peripheral nervous system can be described as neurapraxia, axonotmesis, or neurotmesis.
Concussion is considered a mild form of diffuse axonal injury. Axonal injury can also cause central chromatolysis. The dysfunction of axons in the nervous system is one of the major causes of many inherited and acquired neurological disorders that affect both peripheral and central neurons.
When an axon is crushed, an active process of axonal degeneration takes place at the part of the axon furthest from the cell body. This degeneration takes place quickly following the injury, with the part of the axon being sealed off at the membranes and broken down by macrophages. This is known as Wallerian degeneration. Dying back of an axon can also take place in many neurodegenerative diseases, particularly when axonal transport is impaired, this is known as Wallerian-like degeneration. Studies suggest that the degeneration happens as
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a result of the axonal protein NMNAT2, being prevented from reaching all of the axon.
Demyelination of axons causes the multitude of neurological symptoms found in the disease multiple sclerosis.
Dysmyelination is the abnormal formation of the myelin sheath. This is implicated in several leukodystrophies, and also in schizophrenia.
A severe traumatic brain injury can result in widespread lesions to nerve tracts damaging the axons in a condition known as diffuse axonal injury. This can lead to a persistent vegetative state. It has been shown in studies on the rat that axonal damage from a single mild traumatic brain injury, can leave a susceptibility to further damage, after repeated mild traumatic brain injuries.
A nerve guidance conduit is an artificial means of guiding axon growth to enable neuroregeneration, and is one of the many treatments used for different kinds of nerve injury.
Terminology.
Some general dictionaries define "nerve fiber" as any neuronal process, including both axons and dendrites. However, medical sources generally use "nerve fiber" to refer to the axon only.
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History.
German anatomist Otto Friedrich Karl Deiters is generally credited with the discovery of the axon by distinguishing it from the dendrites. Swiss Rüdolf Albert von Kölliker and German Robert Remak were the first to identify and characterize the axon initial segment. Kölliker named the axon in 1896. Louis-Antoine Ranvier was the first to describe the gaps or nodes found on axons and for this contribution these axonal features are now commonly referred to as the nodes of Ranvier. Santiago Ramón y Cajal, a Spanish anatomist, proposed that axons were the output components of neurons, describing their functionality. Joseph Erlanger and Herbert Gasser earlier developed the classification system for peripheral nerve fibers, based on axonal conduction velocity, myelination, fiber size etc. Alan Hodgkin and Andrew Huxley also employed the squid giant axon (1939) and by 1952 they had obtained a full quantitative description of the ionic basis of the action potential, leading to the formulation of the Hodgkin–Huxley model. Hodgkin and Huxley were awarded jointly the Nobel Prize for this work in 1963. The formulae detailing axonal conductance were extended to vertebrates in the Frankenhaeuser–Huxley equations. The understanding of the biochemical basis for action potential propagation has advanced further, and includes many details about individual ion channels.
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Other animals.
The axons in invertebrates have been extensively studied. The longfin inshore squid, often used as a model organism has the longest known axon. The giant squid has the largest axon known. Its size ranges from 0.5 (typically) to 1 mm in diameter and is used in the control of its jet propulsion system. The fastest recorded conduction speed of 210 m/s, is found in the ensheathed axons of some pelagic Penaeid shrimps and the usual range is between 90 and 200 meters/s (cf 100–120 m/s for the fastest myelinated vertebrate axon.)
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Aramaic alphabet
The ancient Aramaic alphabet was used to write the Aramaic languages spoken by ancient Aramean pre-Christian peoples throughout the Fertile Crescent. It was also adopted by other peoples as their own alphabet when empires and their subjects underwent linguistic Aramaization during a language shift for governing purposes — a precursor to Arabization centuries later — including among the Assyrians and Babylonians who permanently replaced their Akkadian language and its cuneiform script with Aramaic and its script, and among Jews, but not Samaritans, who adopted the Aramaic language as their vernacular and started using the Aramaic alphabet, which they call "Square Script", even for writing Hebrew, displacing the former Paleo-Hebrew alphabet. The modern Hebrew alphabet derives from the Aramaic alphabet, in contrast to the modern Samaritan alphabet, which derives from Paleo-Hebrew.
The letters in the Aramaic alphabet all represent consonants, some of which are also used as "matres lectionis" to indicate long vowels. Writing systems, like the Aramaic, that indicate consonants but do not indicate most vowels other than by means of "matres lectionis" or added diacritical signs, have been called abjads by Peter T. Daniels to distinguish them from alphabets such as the Greek alphabet, that represent vowels more systematically. The term was coined to avoid the notion that a writing system that represents sounds must be either a syllabary or an alphabet, which would imply that a system like Aramaic must be either a syllabary, as argued by Ignace Gelb, or an incomplete or deficient alphabet, as most other writers had said before Daniels. Daniels put forward, this is a different type of writing system, intermediate between syllabaries and 'full' alphabets.
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The Aramaic alphabet is historically significant since virtually all modern Middle Eastern writing systems can be traced back to it. That is primarily due to the widespread usage of the Aramaic language after it was adopted as both a "lingua franca" and the official language of the Neo-Assyrian and Neo-Babylonian Empires, and their successor, the Achaemenid Empire. Among the descendant scripts in modern use, the Jewish Hebrew alphabet bears the closest relation to the Imperial Aramaic script of the 5th century BC, with an identical letter inventory and, for the most part, nearly identical letter shapes. By contrast the Samaritan Hebrew script is directly descended from Proto-Hebrew/Phoenician script, which was the ancestor of the Aramaic alphabet. The Aramaic alphabet was also an ancestor to the Syriac alphabet and Mongolian script and Kharosthi and Brahmi, and Nabataean alphabet, which had the Arabic alphabet as a descendant.
History.
The earliest inscriptions in the Aramaic language use the Phoenician alphabet. Over time, the alphabet developed into the Aramaic alphabet by the 8th century BC. It was used to write the Aramaic languages spoken by ancient Aramean pre-Christian tribes throughout the Fertile Crescent. It was also adopted by other peoples as their own alphabet when empires and their subjects underwent linguistic Aramaization during a language shift for governing purposes — a precursor to Arabization centuries later.
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These include the Assyrians and Babylonians, who permanently replaced their Akkadian language and its cuneiform script with Aramaic and its script, and among Jews, but not Samaritans, who adopted the Aramaic language as their vernacular and started using the Aramaic alphabet even for writing Hebrew, displacing the former Paleo-Hebrew alphabet. The modern Hebrew alphabet derives from the Aramaic alphabet, in contrast to the modern Samaritan alphabet, which derives from Paleo-Hebrew.
Achaemenid Empire (The First Persian Empire).
Around 500 BC, following the Achaemenid conquest of Mesopotamia under Darius I, Old Aramaic was adopted by the Persians as the "vehicle for written communication between the different regions of the vast Persian empire with its different peoples and languages. The use of a single official language, which modern scholarship has dubbed as Official Aramaic, Imperial Aramaic or Achaemenid Aramaic, can be assumed to have greatly contributed to the astonishing success of the Achaemenid Persians in holding their far-flung empire together for as long as they did."
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Imperial Aramaic was highly standardised. Its orthography was based more on historical roots than any spoken dialect and was influenced by Old Persian. The Aramaic glyph forms of the period are often divided into two main styles, the "lapidary" form, usually inscribed on hard surfaces like stone monuments, and a cursive form whose lapidary form tended to be more conservative by remaining more visually similar to Phoenician and early Aramaic. Both were in use through the Achaemenid Persian period, but the cursive form steadily gained ground over the lapidary, which had largely disappeared by the 3rd century BC.
For centuries after the fall of the Achaemenid Empire in 331 BC, Imperial Aramaic, or something near enough to it to be recognisable, remained an influence on the various native Iranian languages. The Aramaic script survived as the essential characteristics of the Iranian Pahlavi writing system.
30 Aramaic documents from Bactria have been recently discovered, an analysis of which was published in November 2006. The texts, which were rendered on leather, reflect the use of Aramaic in the 4th century BC, in the Persian Achaemenid administration of Bactria and Sogdiana.
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The widespread usage of Achaemenid Aramaic in the Middle East led to the gradual adoption of the Aramaic alphabet for writing Hebrew. Formerly, Hebrew had been written using an alphabet closer in form to that of Phoenician, the Paleo-Hebrew alphabet.
Aramaic-derived scripts.
Since the evolution of the Aramaic alphabet out of the Phoenician one was a gradual process, the division of the world's alphabets into the ones derived from the Phoenician one directly, and the ones derived from Phoenician via Aramaic, is somewhat artificial. In general, the alphabets of the Mediterranean region (Anatolia, Greece, Italy) are classified as Phoenician-derived, adapted from around the 8th century BC. Those of the East (the Levant, Persia, Central Asia, and India) are considered Aramaic-derived, adapted from around the 6th century BC from the Imperial Aramaic script of the Achaemenid Empire.
After the fall of the Achaemenid Empire, the unity of the Imperial Aramaic script was lost, diversifying into a number of descendant cursives.
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The Hebrew and Nabataean alphabets, as they stood by the Roman era, were little changed in style from the Imperial Aramaic alphabet. Ibn Khaldun (1332–1406) alleges that not only the old Nabataean writing was influenced by the "Syrian script" (i.e. Aramaic), but also the old Chaldean script.
A cursive Hebrew variant developed from the early centuries AD. It remained restricted to the status of a variant used alongside the noncursive. By contrast, the cursive developed out of the Nabataean alphabet in the same period soon became the standard for writing Arabic, evolving into the Arabic alphabet as it stood by the time of the early spread of Islam.
The development of cursive versions of Aramaic led to the creation of the Syriac, Palmyrene and Mandaic alphabets, which formed the basis of the historical scripts of Central Asia, such as the Sogdian and Mongolian alphabets.
The Old Turkic script is generally considered to have its ultimate origins in Aramaic, in particular via the Pahlavi or Sogdian alphabets, as suggested by V. Thomsen, or possibly via Kharosthi ("cf"., Issyk inscription).
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Brahmi script was also possibly derived or inspired by Aramaic. Brahmic family of scripts includes Devanagari.
Languages using the alphabet.
Today, Biblical Aramaic, Jewish Neo-Aramaic dialects and the Aramaic language of the Talmud are written in the modern-Hebrew alphabet, distinguished from the Old Hebrew script. In classical Jewish literature, the name given to the modern-Hebrew script was "Ashurit", the ancient Assyrian script, a script now known widely as the Aramaic script. It is believed that, during the period of Assyrian dominion, Aramaic script and language received official status.
Syriac and Christian Neo-Aramaic dialects are today written in the Syriac alphabet, which script has superseded the more ancient Assyrian script and now bears its name. Mandaic is written in the Mandaic alphabet. The near-identical nature of the Aramaic and the classical Hebrew alphabets caused Aramaic text to be typeset mostly in the standard Hebrew script in scholarly literature.
Maaloula.
In Maaloula, one of few surviving communities in which a Western Aramaic dialect is still spoken, an Aramaic Language Institute was established in 2006 by Damascus University that teaches courses to keep the language alive.
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Unlike Classical Syriac, which has a rich literary tradition in Syriac-Aramaic script, Western Neo-Aramaic was solely passed down orally for generations until 2006 and was not utilized in a written form.
Therefore, the Language Institute's chairman, George Rizkalla (Rezkallah), undertook the writing of a textbook in Western Neo-Aramaic. Being previously unwritten, Rizkalla opted for the Hebrew alphabet. In 2010, the institute's activities were halted due to concerns that the square Maalouli-Aramaic alphabet used in the program bore a resemblance to the square script of the Hebrew alphabet. As a result, all signs featuring the square Maalouli script were subsequently removed. The program stated that they would instead use the more distinct Syriac-Aramaic alphabet, although use of the Maalouli alphabet has continued to some degree. Al Jazeera Arabic also broadcast a program about Western Neo-Aramaic and the villages in which it is spoken with the square script still in use.
Unicode.
The Imperial Aramaic alphabet was added to the Unicode Standard in October 2009, with the release of version 5.2.
The Unicode block for Imperial Aramaic is U+10840–U+1085F:
The Syriac Aramaic alphabet was added to the Unicode Standard in September 1999, with the release of version 3.0.
The Syriac Abbreviation (a type of overline) can be represented with a special control character called the Syriac Abbreviation Mark (U+070F). The Unicode block for Syriac Aramaic is U+0700–U+074F:
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American shot
An American shot or cowboy shot is a medium-long ("knee") film shot of a group of characters, who are arranged so that all are visible to the camera. It is a translation of a phrase from French film criticism, "." The usual arrangement is for the actors to stand in an irregular line from one side of the screen to the other, with the actors at the end coming forward a little and standing more in profile than the others. The purpose of the composition is to allow complex dialogue scenes to be played out without changes in camera position. In some literature, this is simply referred to as a 3/4 shot.
One of the other main reasons why French critics called it "American shot" was its frequent use in the western genre. This was because a shot that started at knee level would reveal the weapon of a cowboy, usually holstered at their waist. It is the closest the camera can get to an actor while keeping both their face and their holstered gun in frame.
The French critics thought it was characteristic of American films of the 1930s or 1940s; however, it was mostly characteristic of cheaper American movies, such as Charlie Chan mysteries where people collected in front of a fireplace or at the foot of the stairs in order to explain what happened a few minutes ago.
Howard Hawks legitimized this style in his films, allowing characters to act, even when not talking, when most of the audience would not be paying attention. It became his trademark style.
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Acute disseminated encephalomyelitis
Acute disseminated encephalomyelitis (ADEM), or acute demyelinating encephalomyelitis, is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord. As well as causing the brain and spinal cord to become inflamed, ADEM also attacks the nerves of the central nervous system and damages their myelin insulation, which, as a result, destroys the white matter. The cause is often a trigger such as from viral infection or, in extraordinarily rare cases, vaccinations.
ADEM's symptoms resemble the symptoms of multiple sclerosis (MS), so the disease itself is sorted into the classification of the multiple sclerosis borderline diseases. However, ADEM has several features that distinguish it from MS. Unlike MS, ADEM occurs usually in children and is marked with rapid fever, although adolescents and adults can get the disease too. ADEM consists of a single flare-up whereas MS is marked with several flare-ups (or relapses), over a long period of time. Relapses following ADEM are reported in up to a quarter of patients, but the majority of these 'multiphasic' presentations following ADEM likely represent MS. ADEM is also distinguished by a loss of consciousness, coma and death, which is very rare in MS, except in severe cases.
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It affects about 8 per 1,000,000 people per year. Although it occurs in all ages, most reported cases are in children and adolescents, with the average age around 5 to 8 years old. The disease affects males and females almost equally. ADEM shows seasonal variation with higher incidence in winter and spring months which may coincide with higher viral infections during these months. The mortality rate may be as high as 5%; however, full recovery is seen in 50 to 75% of cases with increase in survival rates up to 70 to 90% with figures including minor residual disability as well. The average time to recover from ADEM flare-ups is one to six months.
ADEM produces multiple inflammatory lesions in the brain and spinal cord, particularly in the white matter. Usually these are found in the subcortical and central white matter and cortical gray-white junction of both cerebral hemispheres, cerebellum, brainstem, and spinal cord, but periventricular white matter and gray matter of the cortex, thalami and basal ganglia may also be involved.
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When a person has more than one demyelinating episode of ADEM, the disease is then called recurrent disseminated encephalomyelitis or multiphasic disseminated encephalomyelitis (MDEM). Also, a fulminant course in adults has been described.
Signs and symptoms.
ADEM has an abrupt onset and a monophasic course. Symptoms usually begin 1–3 weeks after infection. Major symptoms include fever, headache, nausea and vomiting, confusion, vision impairment, drowsiness, seizures and coma. Although initially the symptoms are usually mild, they worsen rapidly over the course of hours to days, with the average time to maximum severity being about four and a half days. Additional symptoms include hemiparesis, paraparesis, and cranial nerve palsies.
ADEM in COVID-19.
Neurological symptoms were the main presentation of COVID-19, which did not correlate with the severity of respiratory symptoms. The high incidence of ADEM with hemorrhage is striking. Brain inflammation is likely caused by an immune response to the disease rather than neurotropism. Cerebrospinal fluid analysis was not indicative of an infectious process, neurological impairment was not present in the acute phase of the infection, and neuroimaging findings were not typical of classical toxic and metabolic disorders. The finding of bilateral periventricular relatively asymmetrical lesions allied with deep white matter involvement, that may also be present in cortical gray-white matter junction, thalami, basal ganglia, cerebellum, and brainstem suggests an acute demyelination process. Additionally, hemorrhagic white matter lesions, clusters of macrophages related to axonal injury and ADEM-like appearance were also found in subcortical white matter.
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Causes.
Since the discovery of the anti-MOG specificity against multiple sclerosis diagnosis it is considered that ADEM is one of the possible clinical causes of anti-MOG associated encephalomyelitis.
There are several theories about how the anti-MOG antibodies appear in the patient's serum:
Diagnosis.
The term ADEM has been inconsistently used at different times. Currently, the commonly accepted international standard for the clinical case definition is the one published by the International Pediatric MS Study Group, revision 2007.
Given that the definition is clinical, it is currently unknown if all the cases of ADEM are positive for anti-MOG autoantibody; in any case, it appears to be strongly related to ADEM diagnosis.
Differential diagnosis.
Multiple sclerosis.
While ADEM and MS both involve autoimmune demyelination, they differ in many clinical, genetic, imaging, and histopathological aspects. Some authors consider MS and its borderline forms to constitute a spectrum, differing only in chronicity, severity, and clinical course, while others consider them discretely different diseases.
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Typically, ADEM appears in children following an antigenic challenge and remains monophasic. Nevertheless, ADEM does occur in adults, and can also be clinically multiphasic.
Problems for differential diagnosis increase due to the lack of agreement for a definition of multiple sclerosis. If MS were defined only by the separation in time and space of the demyelinating lesions as McDonald did, it would not be enough to make a difference, as some cases of ADEM satisfy these conditions. Therefore, some authors propose to establish the dividing line as the shape of the lesions around the veins, being therefore "perivenous vs. confluent demyelination".
The pathology of ADEM is very similar to that of MS with some differences. The pathological hallmark of ADEM is perivenous inflammation with limited "sleeves of demyelination". Nevertheless, MS-like plaques (confluent demyelination) can appear
Plaques in the white matter in MS are sharply delineated, while the glial scar in ADEM is smooth. Axons are better preserved in ADEM lesions. Inflammation in ADEM is widely disseminated and ill-defined, and finally, lesions are strictly perivenous, while in MS they are disposed around veins, but not so sharply.
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Nevertheless, the co-occurrence of perivenous and confluent demyelination in some individuals suggests pathogenic overlap between acute disseminated encephalomyelitis and multiple sclerosis and misclassification even with biopsy or even postmortem ADEM in adults can progress to MS
Multiphasic disseminated encephalomyelitis.
When the person has more than one demyelinating episode of ADEM, the disease is then called recurrent disseminated encephalomyelitis or multiphasic disseminated encephalomyelitis (MDEM).
It has been found that anti-MOG auto-antibodies are related to this kind of ADEM
Another variant of ADEM in adults has been described, also related to anti-MOG auto-antibodies, has been named fulminant disseminated encephalomyelitis, and it has been reported to be clinically ADEM, but showing MS-like lesions on autopsy. It has been classified inside the anti-MOG associated inflammatory demyelinating diseases.
Acute hemorrhagic leukoencephalitis.
Acute hemorrhagic leukoencephalitis (AHL, or AHLE), acute hemorrhagic encephalomyelitis (AHEM), acute necrotizing hemorrhagic leukoencephalitis (ANHLE), Weston-Hurst syndrome, or Hurst's disease, is a hyperacute and frequently fatal form of ADEM. AHL is relatively rare (less than 100 cases have been reported in the medical literature ), it is seen in about 2% of ADEM cases, and is characterized by necrotizing vasculitis of venules and hemorrhage, and edema. Death is common in the first week and overall mortality is about 70%, but increasing evidence points to favorable outcomes after aggressive treatment with corticosteroids, immunoglobulins, cyclophosphamide, and plasma exchange. About 70% of survivors show residual neurological deficits, but some survivors have shown surprisingly little deficit considering the extent of the white matter affected.
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This disease has been occasionally associated with ulcerative colitis and Crohn's disease, malaria, sepsis associated with immune complex deposition, methanol poisoning, and other underlying conditions. Also anecdotal association with MS has been reported
Laboratory studies that support diagnosis of AHL are: peripheral leukocytosis, cerebrospinal fluid (CSF) pleocytosis associated with normal glucose and increased protein. On magnetic resonance imaging (MRI), lesions of AHL typically show extensive T2-weighted and fluid-attenuated inversion recovery (FLAIR) white matter hyperintensities with areas of hemorrhages, significant edema, and mass effect.
Treatment.
No controlled clinical trials have been conducted on ADEM treatment, but aggressive treatment aimed at rapidly reducing inflammation of the CNS is standard. The widely accepted first-line treatment is high doses of intravenous corticosteroids, such as methylprednisolone or dexamethasone, followed by 3–6 weeks of gradually lower oral doses of prednisolone. Patients treated with methylprednisolone have shown better outcomes than those treated with dexamethasone. Oral tapers of less than three weeks duration show a higher chance of relapsing, and tend to show poorer outcomes. Other anti-inflammatory and immunosuppressive therapies have been reported to show beneficial effect, such as plasmapheresis, high doses of intravenous immunoglobulin (IVIg), mitoxantrone and cyclophosphamide. These are considered alternative therapies, used when corticosteroids cannot be used or fail to show an effect.
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There is some evidence to suggest that patients may respond to a combination of methylprednisolone and immunoglobulins if they fail to respond to either separately
In a study of 16 children with ADEM, 10 recovered completely after high-dose methylprednisolone, one severe case that failed to respond to steroids recovered completely after IV Ig; the five most severe cases – with ADAM and severe peripheral neuropathy – were treated with combined high-dose methylprednisolone and immunoglobulin, two remained paraplegic, one had motor and cognitive handicaps, and two recovered. A recent review of IVIg treatment of ADEM (of which the previous study formed the bulk of the cases) found that 70% of children showed complete recovery after treatment with IVIg, or IVIg plus corticosteroids. A study of IVIg treatment in adults with ADEM showed that IVIg seems more effective in treating sensory and motor disturbances, while steroids seem more effective in treating impairments of cognition, consciousness and rigor. This same study found one subject, a 71-year-old man who had not responded to steroids, that responded to an IVIg treatment 58 days after disease onset.
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Prognosis.
Full recovery is seen in 50 to 70% of cases, ranging to 70 to 90% recovery with some minor residual disability (typically assessed using measures such as mRS or EDSS), average time to recover is one to six months. The mortality rate may be as high as 5–10%. Poorer outcomes are associated with unresponsiveness to steroid therapy, unusually severe neurological symptoms, or sudden onset. Children tend to have more favorable outcomes than adults, and cases presenting without fevers tend to have poorer outcomes. The latter effect may be due to either protective effects of fever, or that diagnosis and treatment is sought more rapidly when fever is present.
ADEM can progress to MS. It will be considered MS if some lesions appear in different times and brain areas
Motor deficits.
Residual motor deficits are estimated to remain in about 8 to 30% of cases, the range in severity from mild clumsiness to ataxia and hemiparesis.
Neurocognitive.
Patients with demyelinating illnesses, such as MS, have shown cognitive deficits even when there is minimal physical disability. Research suggests that similar effects are seen after ADEM, but that the deficits are less severe than those seen in MS. A study of six children with ADEM (mean age at presentation 7.7 years) were tested for a range of neurocognitive tests after an average of 3.5 years of recovery. All six children performed in the normal range on most tests, including verbal IQ and performance IQ, but performed at least one standard deviation below age norms in at least one cognitive domain, such as complex attention (one child), short-term memory (one child) and internalizing behaviour/affect (two children). Group means for each cognitive domain were all within one standard deviation of age norms, demonstrating that, as a group, they were normal. These deficits were less severe than those seen in similar aged children with a diagnosis of MS.
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Another study compared nineteen children with a history of ADEM, of which 10 were five years of age or younger at the time (average age 3.8 years old, tested an average of 3.9 years later) and nine were older (mean age 7.7y at time of ADEM, tested an average of 2.2 years later) to nineteen matched controls. Scores on IQ tests and educational achievement were lower for the young onset ADEM group (average IQ 90) compared to the late onset (average IQ 100) and control groups (average IQ 106), while the late onset ADEM children scored lower on verbal processing speed. Again, all groups means were within one standard deviation of the controls, meaning that while effects were statistically reliable, the children were as a whole, still within the normal range. There were also more behavioural problems in the early onset group, although there is some suggestion that this may be due, at least in part, to the stress of hospitalization at a young age.
Research.
The relationship between ADEM and anti-MOG associated encephalomyelitis is currently under research. A new entity called MOGDEM has been proposed.
About animal models, the main animal model for MS, experimental autoimmune encephalomyelitis (EAE) is also an animal model for ADEM. Being an acute monophasic illness, EAE is far more similar to ADEM than MS.
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Ataxia
Ataxia (from Greek α- [a negative prefix] + -τάξις [order] = "lack of order") is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements, that indicates dysfunction of parts of the nervous system that coordinate movement, such as the cerebellum.
These nervous system dysfunctions occur in several different patterns, with different results and different possible causes. Ataxia can be limited to one side of the body, which is referred to as hemiataxia. Friedreich's ataxia has gait abnormality as the most commonly presented symptom. Dystaxia is a mild degree of ataxia.
Types.
Cerebellar.
The term cerebellar ataxia is used to indicate ataxia due to dysfunction of the cerebellum. The cerebellum is responsible for integrating a significant amount of neural information that is used to coordinate smoothly ongoing movements and to participate in motor planning. Although ataxia is not present with all cerebellar lesions, many conditions affecting the cerebellum do produce ataxia. People with cerebellar ataxia may have trouble regulating the force, range, direction, velocity, and rhythm of muscle contractions. This results in a characteristic type of irregular, uncoordinated movement that can manifest itself in many possible ways, such as asthenia, asynergy, delayed reaction time, and dyschronometria. Individuals with cerebellar ataxia could also display instability of gait, difficulty with eye movements, dysarthria, dysphagia, hypotonia, dysmetria, and dysdiadochokinesia. These deficits can vary depending on which cerebellar structures have been damaged, and whether the lesion is bi- or unilateral.
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People with cerebellar ataxia may initially present with poor balance, which could be demonstrated as an inability to stand on one leg or perform tandem gait. As the condition progresses, walking is characterized by a widened base and high stepping, as well as staggering and lurching from side to side. Turning is also problematic and could result in falls. As cerebellar ataxia becomes severe, great assistance and effort are needed to stand and walk. Dysarthria, an impairment with articulation, may also be present and is characterized by "scanning" speech that consists of slower rate, irregular rhythm, and variable volume. Also, slurring of speech, tremor of the voice, and ataxic respiration may occur. Cerebellar ataxia could result with incoordination of movement, particularly in the extremities. Overshooting (or hypermetria) occurs with finger-to-nose testing and heel to shin testing; thus, dysmetria is evident. Impairments with alternating movements (dysdiadochokinesia), as well as dysrhythmia, may also be displayed. Tremor of the head and trunk (titubation) may be seen in individuals with cerebellar ataxia.
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Dysmetria is thought to be caused by a deficit in the control of interaction torques in multijoint motion. Interaction torques are created at an associated joint when the primary joint is moved. For example, if a movement required reaching to touch a target in front of the body, flexion at the shoulder would create a torque at the elbow, while extension of the elbow would create a torque at the wrist. These torques increase as the speed of movement increases and must be compensated and adjusted for to create coordinated movement. This may, therefore, explain decreased coordination at higher movement velocities and accelerations.
Sensory.
The term sensory ataxia is used to indicate ataxia due to loss of proprioception, the loss of sensitivity to the positions of joint and body parts. This is generally caused by dysfunction of the dorsal columns of the spinal cord, because they carry proprioceptive information up to the brain. In some cases, the cause of sensory ataxia may instead be dysfunction of the various parts of the brain that receive positional information, including the cerebellum, thalamus, and parietal lobes.
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Sensory ataxia presents itself with an unsteady "stomping" gait with heavy heel strikes, as well as a postural instability that is usually worsened when the lack of proprioceptive input cannot be compensated for by visual input, such as in poorly lit environments.
Physicians can find evidence of sensory ataxia during physical examination by having patients stand with their feet together and eyes shut. In affected patients, this will cause the instability to worsen markedly, producing wide oscillations and possibly a fall; this is called a positive Romberg's test. Worsening of the finger-pointing test with the eyes closed is another feature of sensory ataxia. Also, when patients are standing with arms and hands extended toward the physician, if the eyes are closed, the patients' fingers tend to "fall down" and then be restored to the horizontal extended position by sudden muscular contractions (the "ataxic hand").
Vestibular.
The term vestibular ataxia is used to indicate ataxia due to dysfunction of the vestibular system, which in acute and unilateral cases is associated with prominent vertigo, nausea, and vomiting. In slow-onset, chronic bilateral cases of vestibular dysfunction, these characteristic manifestations may be absent, and dysequilibrium may be the sole presentation.
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Causes.
The three types of ataxia have overlapping causes, so can either coexist or occur in isolation. Cerebellar ataxia can have many causes despite normal neuroimaging.
Focal lesions.
Any type of focal lesion of the central nervous system (such as stroke, brain tumor, multiple sclerosis, inflammatory [such as sarcoidosis], and "chronic lymphocytyc inflammation with pontine perivascular enhancement responsive to steroids syndrome" [CLIPPERS]) will cause the type of ataxia corresponding to the site of the lesion: cerebellar if in the cerebellum; sensory if in the dorsal spinal cord...to include cord compression by thickened ligamentum flavum or stenosis of the boney spinal canal...(and rarely in the thalamus or parietal lobe); or vestibular if in the vestibular system (including the vestibular areas of the cerebral cortex).
Exogenous substances (metabolic ataxia).
Exogenous substances that cause ataxia mainly do so because they have a depressant effect on central nervous system function. The most common example is ethanol (alcohol), which is capable of causing reversible cerebellar and vestibular ataxia. Chronic intake of ethanol causes atrophy of the cerebellum by oxidative and endoplasmic reticulum stresses induced by thiamine deficiency.
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Other examples include various prescription drugs (e.g. most antiepileptic drugs have cerebellar ataxia as a possible adverse effect), Lithium level over 1.5mEq/L, synthetic cannabinoid HU-211 ingestion and various other medical and recreational drugs (e.g. ketamine, PCP or dextromethorphan, all of which are NMDA receptor antagonists that produce a dissociative state at high doses). A further class of pharmaceuticals which can cause short term ataxia, especially in high doses, are benzodiazepines. Exposure to high levels of methylmercury, through consumption of fish with high mercury concentrations, is also a known cause of ataxia and other neurological disorders.
Radiation poisoning.
Ataxia can be induced as a result of severe acute radiation poisoning with an absorbed dose of more than 30 grays. Furthermore, those with ataxia telangiectasia may have a high sensitivity towards gamma rays and x-rays.
Vitamin B12 deficiency.
Vitamin B12 deficiency may cause, among several neurological abnormalities, overlapping cerebellar and sensory ataxia. Neuropsychological symptoms may include sense loss, difficulty in proprioception, poor balance, loss of sensation in the feet, changes in reflexes, dementia, and psychosis, which can be reversible with treatment. Complications may include a neurological complex known as subacute combined degeneration of spinal cord, and other neurological disorders.
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Hypothyroidism.
Symptoms of neurological dysfunction may be the presenting feature in some patients with hypothyroidism. These include reversible cerebellar ataxia, dementia, peripheral neuropathy, psychosis and coma. Most of the neurological complications improve completely after thyroid hormone replacement therapy.
Causes of isolated sensory ataxia.
Peripheral neuropathies may cause generalised or localised sensory ataxia (e.g. a limb only) depending on the extent of the neuropathic involvement. Spinal disorders of various types may cause sensory ataxia from the lesioned level below, when they involve the dorsal columns.
Non-hereditary cerebellar degeneration.
Non-hereditary causes of cerebellar degeneration include chronic alcohol use disorder, head injury, paraneoplastic and non-paraneoplastic autoimmune ataxia, high-altitude cerebral edema, celiac disease, normal-pressure hydrocephalus, and infectious or post-infectious cerebellitis.
Hereditary ataxias.
Ataxia may depend on hereditary disorders consisting of degeneration of the cerebellum or of the spine; most cases feature both to some extent, and therefore present with overlapping cerebellar and sensory ataxia, even though one is often more evident than the other. Hereditary disorders causing ataxia include autosomal dominant ones such as spinocerebellar ataxia, episodic ataxia, and dentatorubropallidoluysian atrophy, as well as autosomal recessive disorders such as Friedreich's ataxia (sensory and cerebellar, with the former predominating) and Niemann–Pick disease, ataxia–telangiectasia (sensory and cerebellar, with the latter predominating), autosomal recessive spinocerebellar ataxia-14 and abetalipoproteinaemia. An example of X-linked ataxic condition is the rare fragile X-associated tremor/ataxia syndrome or FXTAS.
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Arnold–Chiari malformation (congenital ataxia).
Arnold–Chiari malformation is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils and the medulla through the foramen magnum, sometimes causing hydrocephalus as a result of obstruction of cerebrospinal fluid outflow.
Succinic semialdehyde dehydrogenase deficiency.
Succinic semialdehyde dehydrogenase deficiency is an autosomal-recessive gene disorder where mutations in the ALDH5A1 gene results in the accumulation of gamma-Hydroxybutyric acid (GHB) in the body. GHB accumulates in the nervous system and can cause ataxia as well as other neurological dysfunction.
Wilson's disease.
Wilson's disease is an autosomal-recessive gene disorder whereby an alteration of the ATP7B gene results in an inability to properly excrete copper from the body. Copper accumulates in the liver and raises the toxicity levels in the nervous system causing demyelination of the nerves. This can cause ataxia as well as other neurological and organ impairments.
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Gluten ataxia.
Gluten ataxia is an autoimmune disease derived from celiac disease, which is triggered by the ingestion of gluten. Early diagnosis and treatment with a gluten-free diet can improve ataxia and prevent its progression. The effectiveness of the treatment depends on the elapsed time from the onset of the ataxia until diagnosis, because the death of neurons in the cerebellum as a result of gluten exposure is irreversible. It accounts for 40% of ataxias of unknown origin and 15% of all ataxias. Less than 10% of people with gluten ataxia present any gastrointestinal symptom and only about 40% have intestinal damage. This entity is classified into primary auto-immune cerebellar ataxias (PACA). There is a continuum between presymptomatic ataxia and immune ataxias with clinical deficits.
Potassium pump.
Malfunction of the sodium-potassium pump may be a factor in some ataxias. The - pump has been shown to control and set the intrinsic activity mode of cerebellar Purkinje neurons. This suggests that the pump might not simply be a homeostatic, "housekeeping" molecule for ionic gradients; but could be a computational element in the cerebellum and the brain. Indeed, a ouabain block of - pumps in the cerebellum of a live mouse results in it displaying ataxia and dystonia. Ataxia is observed for lower ouabain concentrations, dystonia is observed at higher ouabain concentrations.
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Cerebellar ataxia associated with anti-GAD antibodies.
Antibodies against the enzyme glutamic acid decarboxylase (GAD: enzyme changing glutamate into GABA) cause cerebellar deficits. The antibodies impair motor learning and cause behavioral deficits.
GAD antibodies related ataxia is part of the group called immune-mediated cerebellar ataxias. The antibodies induce a synaptopathy. The cerebellum is particularly vulnerable to autoimmune disorders. Cerebellar circuitry has capacities to compensate and restore function thanks to cerebellar reserve, gathering multiple forms of plasticity. LTDpathies gather immune disorders targeting long-term depression (LTD), a form of plasticity.
Treatment.
The treatment of ataxia and its effectiveness depend on the underlying cause. Treatment may limit or reduce the effects of ataxia, but it is unlikely to eliminate them entirely. Recovery tends to be better in individuals with a single focal injury (such as stroke or a benign tumour), compared to those who have a neurological degenerative condition. A review of the management of degenerative ataxia was published in 2009. A small number of rare conditions presenting with prominent cerebellar ataxia are amenable to specific treatment and recognition of these disorders is critical. Diseases include vitamin E deficiency, abetalipoproteinemia, cerebrotendinous xanthomatosis, Niemann–Pick type C disease, Refsum's disease, glucose transporter type 1 deficiency, episodic ataxia type 2, gluten ataxia, glutamic acid decarboxylase ataxia. Novel therapies target the RNA defects associated with cerebellar disorders, using in particular anti-sense oligonucleotides.
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The movement disorders associated with ataxia can be managed by pharmacological treatments and through physical therapy and occupational therapy to reduce disability. Some drug treatments that have been used to control ataxia include: 5-hydroxytryptophan (5-HTP), idebenone, amantadine, physostigmine, L-carnitine or derivatives, trimethoprim/sulfamethoxazole, vigabatrin, phosphatidylcholine, acetazolamide, 4-aminopyridine, buspirone, and a combination of coenzyme Q10 and vitamin E.
Physical therapy requires a focus on adapting activity and facilitating motor learning for retraining specific functional motor patterns. A recent systematic review suggested that physical therapy is effective, but there is only moderate evidence to support this conclusion. The most commonly used physical therapy interventions for cerebellar ataxia are vestibular habituation, Frenkel exercises, proprioceptive neuromuscular facilitation (PNF), and balance training; however, therapy is often highly individualized and gait and coordination training are large components of therapy.
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Current research suggests that, if a person is able to walk with or without a mobility aid, physical therapy should include an exercise program addressing five components: static balance, dynamic balance, trunk-limb coordination, stairs, and contracture prevention. Once the physical therapist determines that the individual is able to safely perform parts of the program independently, it is important that the individual be prescribed and regularly engage in a supplementary home exercise program that incorporates these components to further improve long term outcomes. These outcomes include balance tasks, gait, and individual activities of daily living. While the improvements are attributed primarily to changes in the brain and not just the hip or ankle joints, it is still unknown whether the improvements are due to adaptations in the cerebellum or compensation by other areas of the brain.
Decomposition, simplification, or slowing of multijoint movement may also be an effective strategy that therapists may use to improve function in patients with ataxia. Training likely needs to be intense and focused—as indicated by one study performed with stroke patients experiencing limb ataxia who underwent intensive upper limb retraining. Their therapy consisted of constraint-induced movement therapy which resulted in improvements of their arm function. Treatment should likely include strategies to manage difficulties with everyday activities such as walking. Gait aids (such as a cane or walker) can be provided to decrease the risk of falls associated with impairment of balance or poor coordination. Severe ataxia may eventually lead to the need for a wheelchair. To obtain better results, possible coexisting motor deficits need to be addressed in addition to those induced by ataxia. For example, muscle weakness and decreased endurance could lead to increasing fatigue and poorer movement patterns.
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There are several assessment tools available to therapists and health care professionals working with patients with ataxia. The International Cooperative Ataxia Rating Scale (ICARS) is one of the most widely used and has been proven to have very high reliability and validity. Other tools that assess motor function, balance and coordination are also highly valuable to help the therapist track the progress of their patient, as well as to quantify the patient's functionality. These tests include, but are not limited to:
Other uses.
The term "ataxia" is sometimes used in a broader sense to indicate lack of coordination in some physiological process. Examples include optic ataxia (lack of coordination between visual inputs and hand movements, resulting in inability to reach and grab objects) and ataxic respiration (lack of coordination in respiratory movements, usually due to dysfunction of the respiratory centres in the medulla oblongata).
Optic ataxia may be caused by lesions to the posterior parietal cortex, which is responsible for combining and expressing positional information and relating it to movement. Outputs of the posterior parietal cortex include the spinal cord, brain stem motor pathways, pre-motor and pre-frontal cortex, basal ganglia and the cerebellum. Some neurons in the posterior parietal cortex are modulated by intention. Optic ataxia is usually part of Balint's syndrome, but can be seen in isolation with injuries to the superior parietal lobule, as it represents a disconnection between visual-association cortex and the frontal premotor and motor cortex.
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Ada Lovelace
Augusta Ada King, Countess of Lovelace ("née" Byron; 10 December 1815 – 27 November 1852), also known as Ada Lovelace, was an English mathematician and writer chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the Analytical Engine. She was the first to recognise that the machine had applications beyond pure calculation.
Lovelace was the only legitimate child of poet Lord Byron and reformer Anne Isabella Milbanke. All her half-siblings, Lord Byron's other children, were born out of wedlock to other women. Lord Byron separated from his wife a month after Ada was born and left England forever. He died in Greece when she was eight. Lady Byron was anxious about her daughter's upbringing and promoted Lovelace's interest in mathematics and logic in an effort to prevent her from developing her father's perceived insanity. Despite this, Lovelace remained interested in her father, naming her two sons Byron and Gordon. Upon her death, she was buried next to her father at her request. Although often ill in her childhood, Lovelace pursued her studies assiduously. She married William King in 1835. King was made Earl of Lovelace in 1838, Ada thereby becoming Countess of Lovelace.
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Lovelace's educational and social exploits brought her into contact with scientists such as Andrew Crosse, Charles Babbage, Sir David Brewster, Charles Wheatstone and Michael Faraday, and the author Charles Dickens, contacts which she used to further her education. Lovelace described her approach as "poetical science" and herself as an "Analyst (& Metaphysician)".
When she was eighteen, Lovelace's mathematical talents led her to a long working relationship and friendship with fellow British mathematician Charles Babbage, who is known as "the father of computers". She was in particular interested in Babbage's work on the Analytical Engine. Lovelace first met him on 5 June 1833, when she and her mother attended one of Charles Babbage's Saturday night soirées with their mutual friend, and Lovelace's private tutor, Mary Somerville.
Between 1842 and 1843, Lovelace translated by the military engineer Luigi Menabrea (later Prime Minister of Italy) about the Analytical Engine, supplementing it with .
Lovelace's notes are important in the early history of computers, especially since the seventh one contained what many consider to be the first computer program—that is, an algorithm designed to be carried out by a machine. Other historians reject this perspective and point out that Babbage's personal notes from 1837 to 1840 contain the first programs for the engine. She also developed a vision of the capability of computers to go beyond mere calculating or number-crunching, while many others, including Babbage himself, focused only on those capabilities. Her mindset of "poetical science" led her to ask questions about the Analytical Engine (as shown in her notes), examining how individuals and society relate to technology as a collaborative tool. The programming language Ada is named after her.
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Biography.
Childhood.
Lord Byron expected his child to be a "glorious boy" and was disappointed when Lady Byron gave birth to a girl. The child was named after Byron's half-sister, Augusta Leigh, and was called "Ada" by Byron himself. On 16 January 1816, at Lord Byron's command, Lady Byron left for her parents' home at Kirkby Mallory, taking their five-week-old daughter with her. Although English law at the time granted full custody of children to the father in cases of separation, Lord Byron made no attempt to claim his parental rights, but did request that his sister keep him informed of Ada's welfare.
On 21 April, Lord Byron signed the deed of separation, although very reluctantly, and left England for good a few days later. Aside from an acrimonious separation, Lady Byron continued throughout her life to make allegations about her husband's immoral behaviour. This set of events made Lovelace infamous in Victorian society. Ada did not have a relationship with her father. He died in 1824 when she was eight years old. Her mother was the only significant parental figure in her life. Lovelace was not shown the family portrait of her father until her 20th birthday.
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Lovelace did not have a close relationship with her mother. She was often left in the care of her maternal grandmother Judith, Hon. Lady Milbanke, who doted on her. However, because of societal attitudes of the time—which favoured the husband in any separation, with the welfare of any child acting as mitigation—Lady Byron had to present herself as a loving mother to the rest of society. This included writing anxious letters to Lady Milbanke about her daughter's welfare, with a cover note saying to retain the letters in case she had to use them to show maternal concern. In one letter to Lady Milbanke, she referred to her daughter as "it": "I talk to it for your satisfaction, not my own, and shall be very glad when you have it under your own." Lady Byron had her teenage daughter watched by close friends for any sign of moral deviation. Lovelace dubbed these observers the "Furies" and later complained they exaggerated and invented stories about her.
Lovelace was often ill, beginning in early childhood. At the age of eight, she experienced headaches that obscured her vision. In June 1829, she was paralyzed after a bout of measles. She was subjected to continuous bed rest for nearly a year, something which may have extended her period of disability. By 1831, she was able to walk with crutches. Despite the illnesses, she developed her mathematical and technological skills.
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Ada Byron had an affair with a tutor in early 1833. She tried to elope with him after she was caught, but the tutor's relatives recognised her and contacted her mother. Lady Byron and her friends covered the incident up to prevent a public scandal. Lovelace never met her younger half-sister, Allegra, the daughter of Lord Byron and Claire Clairmont. Allegra died in 1822 at the age of five. Lovelace did have some contact with Elizabeth Medora Leigh, the daughter of Byron's half-sister Augusta Leigh, who purposely avoided Lovelace as much as possible when introduced at court.
Adult years.
Lovelace became close friends with her tutor Mary Somerville, who introduced her to Charles Babbage in 1833. She had a strong respect and affection for Somerville, and they corresponded for many years. Other acquaintances included the scientists Andrew Crosse, Sir David Brewster, Charles Wheatstone, Michael Faraday and the author Charles Dickens. She was presented at Court at the age of seventeen "and became a popular belle of the season" in part because of her "brilliant mind". By 1834 Ada was a regular at Court and started attending various events. She danced often and was able to charm many people, and was described by most people as being dainty, although John Hobhouse, Byron's friend, described her as "a large, coarse-skinned young woman but with something of my friend's features, particularly the mouth". This description followed their meeting on 24 February 1834 in which Ada made it clear to Hobhouse that she did not like him, probably due to her mother's influence, which led her to dislike all of her father's friends. This first impression was not to last, and they later became friends.
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On 8 July 1835, she married William, 8th Baron King, becoming Lady King. They had three homes: Ockham Park, Surrey; a Scottish estate on Loch Torridon in Ross-shire; and a house in London. They spent their honeymoon at Ashley Combe near Porlock Weir, Somerset, which had been built as a hunting lodge in 1799 and was improved by King in preparation for their honeymoon. It later became their summer retreat and was further improved during this time. From 1845, the family's main house was Horsley Towers, built in the Tudorbethan fashion by the architect of the Houses of Parliament, Charles Barry, and later greatly enlarged to Lovelace's own designs.
They had three children: Byron (born 1836); Anne Isabella (called Annabella, born 1837); and Ralph Gordon (born 1839). Immediately after the birth of Annabella, Lady King experienced "a tedious and suffering illness, which took months to cure". Ada was a descendant of the extinct Barons Lovelace and in 1838, her husband was made Earl of Lovelace and Viscount Ockham, meaning Ada became the Countess of Lovelace. In 1843–44, Ada's mother assigned William Benjamin Carpenter to teach Ada's children and to act as a "moral" instructor for Ada. He quickly fell for her and encouraged her to express any frustrated affections, claiming that his marriage meant he would never act in an "unbecoming" manner. When it became clear that Carpenter was trying to start an affair, Ada cut it off.
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In 1841, Lovelace and Medora Leigh (the daughter of Lord Byron's half-sister Augusta Leigh) were told by Ada's mother that Ada's father was also Medora's father. On 27 February 1841, Ada wrote to her mother: "I am not in the least "astonished". In fact, you merely "confirm" what I have for "years and years" felt scarcely a doubt about, but should have considered it most improper in me to hint to you that I in any way suspected." She did not blame the incestuous relationship on Byron, but instead blamed Augusta Leigh: "I fear she is more inherently wicked than he ever was." In the 1840s, Ada flirted with scandals: firstly, from a relaxed approach to extra-marital relationships with men, leading to rumours of affairs; and secondly, from her love of gambling. She apparently lost more than £3,000 on the horses during the later 1840s. The gambling led to her forming a syndicate with male friends, and an ambitious attempt in 1851 to create a mathematical model for successful large bets. This went disastrously wrong, leaving her thousands of pounds in debt to the syndicate, forcing her to admit it all to her husband. She had a shadowy relationship with Andrew Crosse's son John from 1844 onwards. John Crosse destroyed most of their correspondence after her death as part of a legal agreement. She bequeathed him the only heirlooms her father had personally left to her. During her final illness, she would panic at the idea of the younger Crosse being kept from visiting her.
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Education.
From 1832, when she was seventeen, her mathematical abilities began to emerge, and her interest in mathematics dominated the majority of her adult life. Her mother's obsession with rooting out any of the insanity of which she accused Byron was one of the reasons that Ada was taught mathematics from an early age. She was privately educated in mathematics and science by William Frend, William King, and Mary Somerville, the noted 19th-century researcher and scientific author. In the 1840s, the mathematician Augustus De Morgan extended her "much help in her mathematical studies" including study of advanced calculus topics including the "numbers of Bernoulli" (that formed her celebrated algorithm for Babbage's Analytical Engine). In a letter to Lady Byron, De Morgan suggested that Ada's skill in mathematics might lead her to become "an original mathematical investigator, perhaps of first-rate eminence".
Lovelace often questioned basic assumptions through integrating poetry and science. Whilst studying differential calculus, she wrote to De Morgan:
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I may remark that the curious transformations many formulae can undergo, the unsuspected and to a beginner apparently impossible identity of forms exceedingly dissimilar at first sight, is I think one of the chief difficulties in the early part of mathematical studies. I am often reminded of certain sprites and fairies one reads of, who are at one's elbows in "one" shape now, and the next minute in a form most dissimilar.
Lovelace believed that intuition and imagination were critical to effectively applying mathematical and scientific concepts. She valued metaphysics as much as mathematics, viewing both as tools for exploring "the unseen worlds around us".
Death.
Lovelace died at the age of 36 on 27 November 1852 from cervical cancer (which contemporary accounts called uterine cancer, since a distinction between the two was not made at time). The illness lasted several months, in which time Annabella took command over whom Ada saw, and excluded all of her friends and confidants. Under her mother's influence, Ada had a religious transformation and was coaxed into repenting of her previous conduct and making Annabella her executor. She lost contact with her husband after confessing something to him on 30 August which caused him to abandon her bedside. It is not known what she told him. She was buried, at her request, next to her father at the Church of St. Mary Magdalene in Hucknall, Nottinghamshire.
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Work.
Throughout her life, Lovelace was strongly interested in scientific developments and fads of the day, including phrenology and mesmerism. After her work with Babbage, Lovelace continued to work on other projects. In 1844, she commented to a friend Woronzow Greig about her desire to create a mathematical model for how the brain gives rise to thoughts and nerves to feelings ("a calculus of the nervous system"). She never achieved this, however. In part, her interest in the brain came from a long-running preoccupation, inherited from her mother, about her "potential" madness. As part of her research into this project, she visited the electrical engineer Andrew Crosse in 1844 to learn how to carry out electrical experiments. In the same year, she wrote a review of a paper by Baron Karl von Reichenbach, "Researches on Magnetism", but this was not published and does not appear to have progressed past the first draft. In 1851, the year before her cancer struck, she wrote to her mother mentioning "certain productions" she was working on regarding the relation of maths and music.
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Lovelace first met Charles Babbage in June 1833, through their mutual friend Mary Somerville. Later that month, Babbage invited Lovelace to see the prototype for his difference engine. She became fascinated with the machine and used her relationship with Somerville to visit Babbage as often as she could. Babbage was impressed by Lovelace's intellect and analytic skills. He called her "The Enchantress of Number". In 1843, he wrote to her:
During a nine-month period in 1842–43, Lovelace translated the Italian mathematician Luigi Menabrea's article on Babbage's newest proposed machine, the Analytical Engine. With the article, she appended a set of notes. Explaining the Analytical Engine's function was a difficult task; many other scientists did not grasp the concept and the British establishment had shown little interest in it. Lovelace's notes even had to explain how the Analytical Engine differed from the original Difference Engine. Her work was well received at the time; the scientist Michael Faraday described himself as a supporter of her writing.
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The notes are around three times longer than the article itself and include (in "Note G"), in complete detail, a method for calculating a sequence of Bernoulli numbers using the Analytical Engine, which might have run correctly had it ever been built (only Babbage's Difference Engine has been built, completed in London in 2002). Based on this work, Lovelace is now considered by many to be the first computer programmer and her method has been called the world's first computer program.
"Note G" also contains Lovelace's dismissal of artificial intelligence. She wrote that "The Analytical Engine has no pretensions whatever to "originate" anything. It can do "whatever we know how to order it" to perform. It can follow analysis; but it has no power of anticipating any analytical relations or truths." This objection has been the subject of much debate and rebuttal, for example by Alan Turing in his paper "Computing Machinery and Intelligence". Most modern computer scientists argue that this view is outdated and that computer software can develop in ways that cannot necessarily be anticipated by programmers.
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Lovelace and Babbage had a minor falling out when the papers were published, when he tried to leave his own statement (criticising the government's treatment of his Engine) as an unsigned preface, which could have been mistakenly interpreted as a joint declaration. When Taylor's "Scientific Memoirs" ruled that the statement should be signed, Babbage wrote to Lovelace asking her to withdraw the paper. This was the first that she knew he was leaving it unsigned, and she wrote back refusing to withdraw the paper. The historian Benjamin Woolley theorised that "His actions suggested he had so enthusiastically sought Ada's involvement, and so happily indulged her ... because of her 'celebrated name'." Their friendship recovered, and they continued to correspond. On 12 August 1851, when she was dying of cancer, Lovelace wrote to him asking him to be her executor, though this letter did not give him the necessary legal authority. Part of the terrace at Worthy Manor was known as "Philosopher's Walk;" it was there that Lovelace and Babbage were reputed to have walked while discussing mathematical principles.
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First published computer program.
In 1840, Babbage was invited to give a seminar at the University of Turin about his Analytical Engine. Luigi Menabrea, a young Italian engineer and the future Prime Minister of Italy, transcribed Babbage's lecture into French, and this transcript was subsequently published in the "Bibliothèque universelle de Genève" in October 1842.
Babbage's friend Charles Wheatstone commissioned Ada Lovelace to translate Menabrea's paper into English. She then augmented the paper with notes, which were added to the translation. Ada Lovelace spent the better part of a year doing this, assisted with input from Babbage. These notes, which are more extensive than Menabrea's paper, were then published in the September 1843 edition of Taylor's "Scientific Memoirs" under the initialism "AAL".
Ada Lovelace's notes were labelled alphabetically from A to G. In Note G, she describes an algorithm for the Analytical Engine to compute Bernoulli numbers. It is considered to be the first published algorithm ever specifically tailored for implementation on a computer, and Ada Lovelace has often been cited as the first computer programmer for this reason. However, Babbage claims credit for this portion of the paper in his autobiography. The engine was never completed and so the program was never tested.
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In 1953, more than a century after her death, Ada Lovelace's notes on Babbage's Analytical Engine were republished as an appendix to B. V. Bowden's "Faster than Thought: A Symposium on Digital Computing Machines". The engine has now been recognised as an early model for a computer and her notes as a description of a computer and software.
Insight into potential of computing devices.
In her notes, Ada Lovelace emphasised the difference between the Analytical Engine and previous calculating machines, particularly its ability to be programmed to solve problems of any complexity. She realised the potential of the device extended far beyond mere number crunching. In her notes, she wrote:
This analysis was an important development from previous ideas about the capabilities of computing devices and anticipated the implications of modern computing one hundred years before they were realised. Walter Isaacson ascribes Ada's insight regarding the application of computing to "any" process based on logical symbols to an observation about textiles: "When she saw some mechanical looms that used punchcards to direct the weaving of beautiful patterns, it reminded her of how Babbage's engine used punched cards to make calculations." This insight is seen as significant by writers such as Betty Toole and Benjamin Woolley, as well as the programmer John Graham-Cumming, whose project Plan 28 has the aim of constructing the first complete Analytical Engine.
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According to the historian of computing and Babbage specialist Doron Swade:
Ada saw something that Babbage in some sense failed to see. In Babbage's world his engines were bound by number...What Lovelace saw...was that number could represent entities other than quantity. So once you had a machine for manipulating numbers, if those numbers represented other things, letters, musical notes, then the machine could manipulate symbols of which number was one instance, according to rules. It is this fundamental transition from a machine which is a number cruncher to a machine for manipulating symbols according to rules that is the fundamental transition from calculation to computation—to general-purpose computation—and looking back from the present high ground of modern computing, if we are looking and sifting history for that transition, then that transition was made explicitly by Ada in that 1843 paper.
Distinction between mechanism and logical structure.
Lovelace recognized the difference between the details of the computing mechanism, as covered in an 1834 article on the Difference Engine,
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and the logical structure of the Analytical Engine, on which the article she was reviewing dwelt. She noted that different specialists might be required in each area.
The [1834 article] chiefly treats it under its mechanical aspect, entering but slightly into the mathematical principles of which that engine is the representative, but giving, in considerable length, many details of the mechanism and contrivances by means of which it tabulates the various orders of differences. M. Menabrea, on the contrary, exclusively developes the analytical view; taking it for granted that mechanism is able to perform certain processes, but without attempting to explain how; and devoting his whole attention to explanations and illustrations of the manner in which analytical laws can be so arranged and combined as to bring every branch of that vast subject within the grasp of the assumed powers of mechanism. It is obvious that, in the invention of a calculating engine, these two branches of the subject are equally essential fields of investigation... They are indissolubly connected, though so different in their intrinsic nature, that perhaps the same mind might not be likely to prove equally profound or successful in both.
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Controversy over contribution.
Though Lovelace is often referred to as the first computer programmer, some biographers, computer scientists and historians of computing suggest otherwise.
Allan G. Bromley, in the 1990 article "Difference and Analytical Engines":
Bruce Collier wrote that Lovelace "made a considerable contribution to publicizing the Analytical Engine, but there is no evidence that she advanced the design or theory of it in any way".
Eugene Eric Kim and Betty Alexandra Toole consider it "incorrect" to regard Lovelace as the first computer programmer, as Babbage wrote the initial programs for his Analytical Engine, although the majority were never published. Bromley notes several dozen sample programs prepared by Babbage between 1837 and 1840, all substantially predating Lovelace's notes. Dorothy K. Stein regards Lovelace's notes as "more a reflection of the mathematical uncertainty of the author, the political purposes of the inventor, and, above all, of the social and cultural context in which it was written, than a blueprint for a scientific development".
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Doron Swade has said that Ada only published the first computer program instead of actually writing it, but agrees that she was the only person to see the potential of the analytical engine as a machine capable of expressing entities other than quantities.
In his book, "Idea Makers", Stephen Wolfram defends Lovelace's contributions. While acknowledging that Babbage wrote several unpublished algorithms for the Analytical Engine prior to Lovelace's notes, Wolfram argues that "there's nothing as sophisticated—or as clean—as Ada's computation of the Bernoulli numbers. Babbage certainly helped and commented on Ada's work, but she was definitely the driver of it." Wolfram then suggests that Lovelace's main achievement was to distill from Babbage's correspondence "a clear exposition of the abstract operation of the machine—something which Babbage never did".
Commemoration.
The computer language Ada, created on behalf of the United States Department of Defense, was named after Lovelace. The reference manual for the language was approved on 10 December 1980 and the Department of Defense Military Standard for the language, "MIL-STD-1815", was given the number of the year of her birth.
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In 1981, the Association for Women in Computing inaugurated its Ada Lovelace Award. , the British Computer Society (BCS) has awarded the Lovelace Medal, and in 2008 initiated an annual competition for women students. BCSWomen sponsors the Lovelace Colloquium, an annual conference for women undergraduates. Ada College is a further-education college in Tottenham Hale, London, focused on digital skills.
Ada Lovelace Day is an annual event celebrated on the second Tuesday of October, which began in 2009. Its goal is to "... raise the profile of women in science, technology, engineering, and maths," and to "create new role models for girls and women" in these fields.
The Ada Initiative was a non-profit organisation dedicated to increasing the involvement of women in the free culture and open source movements. A specialist technical college, for pupils aged 16–19, in England is named "Ada, the National College for Digital Skills", it has campuses in Whitechapel, Tottenham Hale and Manchester. The building of the department of Engineering Mathematics at the University of Bristol is called the Ada Lovelace Building. The Engineering in Computer Science and Telecommunications College building in Zaragoza University is called the Ada Byron Building. The computer centre in the village of Porlock, near where Lovelace lived, is named after her. Ada Lovelace House is a council-owned building in Kirkby-in-Ashfield, Nottinghamshire, near where Lovelace spent her infancy.
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In 2012, a Google Doodle and blog post honoured her on her birthday. In 2013, Ada Developers Academy was founded and named after her. Its mission is to diversify tech by providing women and gender-diverse people the skills, experience, and community support to become professional software developers to change the face of tech. On 17 September 2013, the BBC Radio 4 biography programme "Great Lives" devoted an episode to Ada Lovelace; she was sponsored by TV presenter Konnie Huq.
As of November 2015, all new British passports have included an illustration of Lovelace and Babbage. In 2017, a Google Doodle honoured her with other women on International Women's Day. On 2 February 2018, Satellogic, a high-resolution Earth observation imaging and analytics company, launched a ÑuSat type micro-satellite named in honour of Ada Lovelace. In March 2018, "The New York Times" published a belated obituary for Ada Lovelace.
On 27 July 2018, Senator Ron Wyden submitted, in the United States Senate, the designation of 9 October 2018 as National Ada Lovelace Day: "To honor the life and contributions of Ada Lovelace as a leading woman in science and mathematics". The resolution (S.Res.592) was considered, and agreed to without amendment and with a preamble by unanimous consent. In November 2020 it was announced that Trinity College Dublin, whose library had previously held forty busts, all of them of men, was commissioning four new busts of women, one of whom was to be Lovelace.
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In March 2022, a statue of Ada Lovelace was installed at the site of the former Ergon House in the City of Westminster, London, honoring its scientific history. The redevelopment was part of a complex with Imperial Chemical House. The statue was sculpted by Etienne and Mary Millner and based on the portrait by Margaret Sarah Carpenter. The sculpture was unveiled on International Women's Day, 2022. It stands on the 7th floor of Millbank Quarter overlooking the junction of Dean Bradley Street and Horseferry Road.
In September 2022, Nvidia announced the Ada Lovelace graphics processing unit (GPU) microarchitecture. In July 2023, the Royal Mint issued four commemorative £2 coins in various metals to "honour the innovative contributions of computer science visionary Ada Lovelace and her legacy as a female trailblazer."
Bicentenary (2015).
The bicentenary of Ada Lovelace's birth was celebrated with a number of events, including:
Special exhibitions were displayed by the Science Museum in London, England and the Weston Library (part of the Bodleian Library) in Oxford, England.
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In popular culture.
Novels and plays.
Lovelace is portrayed in Romulus Linney's 1977 play "Childe Byron". In Tom Stoppard's 1993 play "Arcadia", the precocious teenage genius Thomasina Coverly—a character "apparently based" on Ada Lovelace (the play also involves Lord Byron)—comes to understand chaos theory, and theorises the second law of thermodynamics, before either is officially recognised.
In the 1990 steampunk novel "The Difference Engine" by William Gibson and Bruce Sterling, Lovelace delivers a lecture on the "punched cards" programme which proves Gödel's incompleteness theorems decades before their actual discovery. Lovelace and Mary Shelley as teenagers are the central characters in Jordan Stratford's steampunk series, "The Wollstonecraft Detective Agency".
Lovelace features in John Crowley's 2005 novel, "Lord Byron's Novel: The Evening Land", as an unseen character whose personality is forcefully depicted in her annotations and anti-heroic efforts to archive her father's lost novel.
The 2015 play "Ada and the Engine" by Lauren Gunderson portrays Lovelace and Charles Babbage in unrequited love, and it imagines a post-death meeting between Lovelace and her father. Lovelace and Babbage are also the main characters in Sydney Padua's webcomic and graphic novel "The Thrilling Adventures of Lovelace and Babbage". The comic features extensive footnotes on the history of Ada Lovelace, and many lines of dialogue are drawn from actual correspondence.
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Film and television.
In the 1997 film "Conceiving Ada", a computer scientist obsessed with Ada finds a way of communicating with her in the past by means of "undying information waves".
Lovelace, identified as Ada Augusta Byron, is portrayed by Lily Lesser in the second series of "The Frankenstein Chronicles" aired on ITV in 2017. She is employed as an "analyst" to provide the workings of a life-sized humanoid automaton. The brass workings of the machine are reminiscent of Babbage's analytical engine. Her employment is described as keeping her occupied until she returns to her studies in advanced mathematics.
Lovelace and Babbage appear as characters in the second season of the ITV series "Victoria" (2017). Emerald Fennell portrays Lovelace in the episode, "The Green-Eyed Monster."
"Lovelace" is the name of the operating system designed by the character Cameron Howe in "Halt and Catch Fire", which aired on AMC in the US in 2015.
Lovelace features as a character in "Spyfall, Part 2", the second episode of "Doctor Who", series 12, which first aired on BBC One on 5 January 2020. The character was portrayed by Sylvie Briggs, alongside characterisations of Charles Babbage and Noor Inayat Khan.
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Publications.
Publication history.
Six copies of the 1843 first edition of "Sketch of the Analytical Engine" with Ada Lovelace's "Notes" have been located. Three are held at Harvard University, one at the University of Oklahoma, and one at the United States Air Force Academy. On 20 July 2018, the sixth copy was sold at auction to an anonymous buyer for £95,000. A digital facsimile of one of the copies in the Harvard University Library is available online.
In December 2016, a letter written by Ada Lovelace was forfeited by Martin Shkreli to the New York State Department of Taxation and Finance for unpaid taxes owed by Shkreli.
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August Derleth
August William Derleth (February 24, 1909 – July 4, 1971) was an American writer and anthologist. He was the first book publisher of the writings of H. P. Lovecraft. He made contributions to the Cthulhu Mythos and the cosmic horror genre and helped found Arkham House, a publishing company which did much to introduce hardcover prints of United Kingdom supernatural fiction works to the United States. Derleth was also a leading American regional writer of his day, as well as prolific in several other genres, including historical fiction, poetry, detective fiction, science fiction, and biography. Notably, he created the fictional detective Solar Pons, a pastiche of Arthur Conan Doyle's Sherlock Holmes.
A 1938 Guggenheim Fellow, Derleth considered his most serious work to be the ambitious "Sac Prairie Saga", a series of fiction, historical fiction, poetry, and non-fiction naturalist works designed to memorialize life in the Wisconsin he knew. Derleth can also be considered a pioneering naturalist and conservationist in his writing.
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Life.
The son of William Julius Derleth and Rose Louise Volk, Derleth grew up in Sauk City, Wisconsin. He was educated in local parochial and public high school. Derleth wrote his first fiction at age 13. He was interested most in reading, and he made three trips to the library a week. He would save his money to buy books (his personal library exceeded 12,000 volumes later on in life). Some of his biggest influences were Ralph Waldo Emerson's essays, Walt Whitman, H. L. Mencken's "The American Mercury", Samuel Johnson's "The History of Rasselas, Prince of Abissinia", Alexandre Dumas, Edgar Allan Poe, Walter Scott, and Henry David Thoreau's Walden.
Forty rejected stories and three years later, according to anthologist Jim Stephens, he sold his first story, "Bat's Belfry", to "Weird Tales" magazine in 1926. Derleth wrote throughout his four years at the University of Wisconsin, where he received a B.A. in 1930. During this time he also served briefly as associate editor of Minneapolis-based Fawcett Publications "Mystic Magazine".
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Returning to Sauk City in the summer of 1931, Derleth worked in a local canning factory and collaborated with childhood friend Mark Schorer (later Chairman of the University of California, Berkeley English Department). They rented a cabin, writing Gothic and other horror stories and selling them
to "Weird Tales" magazine. Derleth won a place on the O'Brien Roll of Honor for "Five Alone", published in "Place of Hawks", but was first published in "Pagany" magazine.
As a result of his early work on the "Sac Prairie Saga", Derleth was awarded the prestigious Guggenheim Fellowship; his sponsors were Helen C. White, Nobel Prize-winning novelist Sinclair Lewis and poet Edgar Lee Masters of "Spoon River Anthology" fame.
In the mid-1930s, Derleth organized a Ranger's Club for young people, served as clerk and president of the local school board, served as a parole officer, organized a local men's club and a parent-teacher association. He also lectured in American regional literature at the University of Wisconsin and was a contributing editor of "Outdoors Magazine".
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With longtime friend Donald Wandrei, Derleth founded Arkham House in 1939. Its initial objective was to publish the works of H. P. Lovecraft, with whom Derleth had corresponded since his teenage years. At the same time, he began teaching a course in American Regional Literature at the University of Wisconsin.
In 1941, he became literary editor of "The Capital Times" newspaper in Madison, a post he held until his resignation in 1960. His hobbies included fencing, swimming, chess, philately and comic-strips (Derleth reportedly used the funding from his Guggenheim Fellowship to bind his comic book collection, most recently valued in the millions of dollars, rather than to travel abroad as the award intended.). Derleth's true avocation, however, was hiking the terrain of his native Wisconsin lands, and observing and recording nature with an expert eye.
Derleth once wrote of his writing methods, "I write very swiftly, from 750,000 to a million words yearly, very little of it pulp material."
In 1948, he was elected president of the Associated Fantasy Publishers at the 6th World Science Fiction Convention in Toronto.
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He was married April 6, 1953, to Sandra Evelyn Winters. They divorced six years later. Derleth retained custody of the couple's two children, April Rose Derleth and Walden William Derleth. April earned a Bachelor of Arts degree in English from the University of Wisconsin-Madison in 1977. She became majority stockholder, President, and CEO of Arkham House in 1994. She remained in that capacity until her death. She was known in the community as a naturalist and humanitarian. April died on March 21, 2011.
In 1960, Derleth began editing and publishing a magazine called "Hawk and Whippoorwill", dedicated to poems of man and nature.
Derleth died of a heart attack on July 4, 1971, and is buried in St. Aloysius Cemetery in Sauk City. The U.S. 12 bridge over the Wisconsin River is named in his honor. Derleth was Roman Catholic.
In Derleth's biography, Dorothy M. Grobe Litersky stated that Derleth was bisexual, and maintained long-term romantic relationships with both men and women. This assertion has not been verified; no names were given of these romantic partners (in the interest of privacy according to Litersky), and no evidence or acknowledgement of Derleth having a bisexual or homosexual orientation has ever been found in his personal correspondence.
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Career.
Derleth wrote more than 150 short stories and more than 100 books during his lifetime.
The "Sac Prairie Saga".
Derleth wrote an expansive series of novels, short stories, journals, poems, and other works about Sac Prairie. Derleth intended this series to comprise up to 50 novels telling the projected life-story of the region from the 19th century onwards, with analogies to Balzac's "Human Comedy" and Proust's "Remembrance of Things Past".
This, and other early work by Derleth, made him a well-known figure among the regional literary figures of his time: early Pulitzer Prize winners Hamlin Garland and Zona Gale, as well as Sinclair Lewis, the last both an admirer and critic of Derleth.
As Edward Wagenknecht wrote in "Cavalcade of the American Novel", "What Mr. Derleth has that is lacking...in modern novelists generally, is a country. He belongs. He writes of a land and a people that are bone of his bone and flesh of his flesh. In his fictional world, there is a unity much deeper and more fundamental than anything that can be conferred by an ideology. It is clear, too, that he did not get the best, and most fictionally useful, part of his background material from research in the library; like Scott, in his Border novels, he gives, rather, the impression of having drunk it in with his mother's milk."
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Jim Stephens, editor of "An August Derleth Reader", (1992), argues: "what Derleth accomplished...was to gather a Wisconsin mythos which gave respect to the ancient fundament of our contemporary life."
The author inaugurated the "Sac Prairie Saga" with four novellas comprising "Place of Hawks", published by Loring & Mussey in 1935. At publication, "The Detroit News" wrote: "Certainly with this book Mr. Derleth may be added to the American writers of distinction."
Derleth's first novel, "Still is the Summer Night", was published two years later by the famous Charles Scribners' editor Maxwell Perkins, and was the second in his Sac Prairie Saga.
"Village Year", the first in a series of journals – meditations on nature, Midwestern village American life, and more – was published in 1941 to praise from "The New York Times Book Review": "A book of instant sensitive responsiveness...recreates its scene with acuteness and beauty, and makes an unusual contribution to the Americana of the present day." The "New York Herald Tribune" observed that "Derleth...deepens the value of his village setting by presenting in full the enduring natural background; with the people projected against this, the writing comes to have the quality of an old Flemish picture, humanity lively and amusing and loveable in the foreground and nature magnificent beyond." James Grey, writing in the "St. Louis Dispatch" concluded, "Derleth has achieved a kind of prose equivalent of the "Spoon River Anthology"."
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In the same year, "Evening in Spring" was published by Charles Scribners & Sons. This work Derleth considered among his finest. What "The Milwaukee Journal" called "this beautiful little love story", is an autobiographical novel of first love beset by small-town religious bigotry. The work received critical praise: "The New Yorker" considered it a story told "with tenderness and charm", while the "Chicago Tribune" concluded: "It's as though he turned back the pages of an old diary and told, with rekindled emotion, of the pangs of pain and the sharp, clear sweetness of a boy's first love." Helen Constance White, wrote in "The Capital Times" that it was "...the best articulated, the most fully disciplined of his stories."
These were followed in 1943 with "Shadow of Night", a Scribners' novel of which "The Chicago Sun" wrote: "Structurally it has the perfection of a carved jewel...A psychological novel of the first order, and an adventure tale that is unique and inspiriting."
In November 1945, however, Derleth's work was attacked by his one-time admirer and mentor, Sinclair Lewis. Writing in "Esquire", Lewis observed, "It is a proof of Mr. Derleth's merit that he makes one want to make the journey and see his particular Avalon: The Wisconsin River shining among its islands, and the castles of Baron Pierneau and Hercules Dousman. He is a champion and a justification of regionalism. Yet he is also a burly, bounding, bustling, self-confident, opinionated, and highly-sweatered young man with faults so grievous that a melancholy perusal of them may be of more value to apprentices than a study of his serious virtues. If he could ever be persuaded that he isn't half as good as he thinks he is, if he would learn the art of sitting still and using a blue pencil, he might become twice as good as he thinks he is – which would about rank him with Homer." Derleth good-humoredly reprinted the criticism along with a photograph of himself sans sweater, on the back cover of his 1948 country journal: "Village Daybook".
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A lighter side to the "Sac Prairie Saga" is a series of quasi-autobiographical short stories known as the "Gus Elker Stories", amusing tales of country life that Peter Ruber, Derleth's last editor, said were "...models of construction and...fused with some of the most memorable characters in American literature." Most were written between 1934 and the late 1940s, though the last, "Tail of the Dog", was published in 1959 and won the "Scholastic Magazine" short story award for the year. The series was collected and republished in "Country Matters" in 1996.
"Walden West", published in 1961, is considered by many Derleth's finest work. This prose meditation is built out of the same fundamental material as the series of Sac Prairie journals, but is organized around three themes: "the persistence of memory...the sounds and odors of the country...and Thoreau's observation that the 'mass of men lead lives of quiet desperation. A blend of nature writing, philosophic musings, and careful observation of the people and place of "Sac Prairie". Of this work, George Vukelich, author of "North Country Notebook", writes: "Derleth's "Walden West" is...the equal of Sherwood Anderson's "Winesburg,Ohio", Thornton Wilder's "Our Town", and Edgar Lee Masters' "Spoon River Anthology"." This was followed eight years later by "Return to Walden West", a work of similar quality, but with a more noticeable environmentalist edge to the writing, notes critic Norbert Blei.
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A close literary relative of the "Sac Prairie Saga" was Derleth's "Wisconsin Saga", which comprises several historical novels.
Detective fiction and "Solar Pons".
Detective fiction represented another substantial body of Derleth's work. Most notable among this work was a series of 70 stories in affectionate pastiche of Sherlock Holmes, whose creator, Sir Arthur Conan Doyle, he admired greatly. The stories feature a Holmes-styled British detective named Solar Pons, of 7B Praed Street in London. These included one published novel as well ("Mr. Fairlie's Final Journey"). The series was greatly admired by such notable writers and critics of mystery and detective fiction as Ellery Queen (Frederic Dannay), Anthony Boucher, Vincent Starrett, and Howard Haycraft.
In his 1944 volume "The Misadventures of Sherlock Holmes", Ellery Queen wrote of Derleth's "The Norcross Riddle", an early Pons story: "How many budding authors, not even old enough to vote, could have captured the spirit and atmosphere with as much fidelity?" Queen adds, "his choice of the euphonic Solar Pons is an appealing addition to the fascinating lore of Sherlockian nomenclature." Vincent Starrett, in his foreword to the 1964 edition of "The Casebook of Solar Pons", wrote that the series is "as sparkling a galaxy of Sherlockian pastiches as we have had since the canonical entertainments came to an end."
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Despite close similarities to Doyle's creation, Pons lived in the post-World War I era, in the decades of the 1920s and 1930s. Though Derleth never wrote a Pons novel to equal "The Hound of the Baskervilles", editor Peter Ruber wrote that "Derleth" produced more than a few Solar Pons stories almost as good as Sir Arthur's, and many that had better plot construction."
Although these stories were a form of diversion for Derleth, Ruber, who edited "The Original Text Solar Pons Omnibus Edition" (2000), argued: "Because the stories were generally of such high quality, they ought to be assessed on their own merits as a unique contribution in the annals of mystery fiction, rather than suffering comparison as one of the endless imitators of Sherlock Holmes."
Some of the stories were self-published, through a new imprint called "Mycroft & Moran", an appellation of humorous significance to Holmesian scholars. For approximately a decade, an active supporting group was the Praed Street Irregulars, patterned after the Baker Street Irregulars.
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In 1946, Conan Doyle's two sons made some attempts to force Derleth to cease publishing the Solar Pons series, but the efforts were unsuccessful, and were eventually withdrawn.
Derleth's mystery and detective fiction also included a series of works set in Sac Prairie and featuring Judge Peck as the central character.
Youth and children's fiction.
Derleth wrote many and varied children's works, including biographies meant to introduce younger readers to explorer Jacques Marquette, as well as Ralph Waldo Emerson and Henry David Thoreau. Arguably most important among his works for younger readers, however, is the Steve and Sim Mystery Series, also known as the Mill Creek Irregulars series. The ten-volume series, published between 1958 and 1970, is set in Sac Prairie of the 1920s and can thus be considered in its own right a part of the "Sac Prairie Saga", as well as an extension of Derleth's body of mystery fiction. Robert Hood, writing in the "New York Times" said: "Steve and Sim, the major characters, are twentieth-century cousins of Huck Finn and Tom Sawyer; Derleth's minor characters, little gems of comic drawing." The first novel in the series, "The Moon Tenders", does, in fact, involve a rafting adventure down the Wisconsin River, which led regional writer Jesse Stuart to suggest the novel was one that "older people might read to recapture the spirit and dream of youth." The connection to the "Sac Prairie Saga" was noted by the "Chicago Tribune": "Once again a small midwest community in 1920s is depicted with perception, skill, and dry humor."
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Arkham House and the "Cthulhu Mythos".
Derleth was a correspondent and friend of H. P. Lovecraft – when Lovecraft wrote about "le Comte d'Erlette" in his fiction, it was in homage to Derleth. Derleth invented the term "Cthulhu Mythos" to describe the fictional universe depicted in the series of stories shared by Lovecraft and other writers in his circle.
When Lovecraft died in 1937, Derleth and Donald Wandrei assembled a collection of Lovecraft's stories and tried to get them published. Existing publishers showed little interest, so Derleth and Wandrei founded Arkham House in 1939 for that purpose. The name of the company derived from Lovecraft's fictional town of Arkham, Massachusetts, which features in many of his stories. In 1939, Arkham House published "The Outsider and Others", a huge collection that contained most of Lovecraft's known short stories. Derleth and Wandrei soon expanded Arkham House and began a regular publishing schedule after its second book, "Someone in the Dark", a collection of some of Derleth's own horror stories, was published in 1941.
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Following Lovecraft's death, Derleth wrote a number of stories based on fragments and notes left by Lovecraft. These were published in "Weird Tales" and later in book form, under the byline "H. P. Lovecraft and August Derleth", with Derleth calling himself a "posthumous collaborator". This practice has raised objections in some quarters that Derleth simply used Lovecraft's name to market what was essentially his own fiction; S. T. Joshi refers to the "posthumous collaborations" as marking the beginning of "perhaps the most disreputable phase of Derleth's activities".
Dirk W. Mosig, S. T. Joshi, and Richard L. Tierney were dissatisfied with Derleth's invention of the term "Cthulhu Mythos" (Lovecraft himself used "Yog-Sothothery") and his presentation of Lovecraft's fiction as having an overall pattern reflecting Derleth's own Christian world view, which they contrast with Lovecraft's depiction of an amoral universe. However, Robert M. Price points out that while Derleth's tales are distinct from Lovecraft's in their use of hope and his depiction of a struggle between good and evil, nevertheless the basis of Derleth's systemization are found in Lovecraft. He also suggests that the differences can be overstated:
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Derleth "was" more optimistic than Lovecraft in his conception of the Mythos, but we are dealing with a difference more of degree than kind. There are indeed tales wherein Derleth's protagonists get off scot-free (like "The Shadow in the Attic", "Witches' Hollow", or "The Shuttered Room"), but often the hero is doomed (e.g., "The House in the Valley", "The Peabody Heritage", "Something in Wood"), as in Lovecraft. And it must be remembered that an occasional Lovecraftian hero does manage to overcome the odds, e.g., in "The Horror in the Museum", "The Shunned House", and 'The Case of Charles Dexter Ward'.
Derleth also treated Lovecraft's Great Old Ones as representatives of elemental forces, creating new fictional entities to flesh out this framework.
Such debates aside, Derleth's founding of Arkham House and his successful effort to rescue Lovecraft from literary oblivion are widely acknowledged by practitioners in the horror field as seminal events in the field. For instance, Ramsey Campbell has acknowledged Derleth's encouragement and guidance during the early part of his own writing career, and Kirby McCauley has cited Derleth and Arkham House as an inspiration for his own anthology "Dark Forces". Arkham House and Derleth published "Dark Carnival", the first book by Ray Bradbury, as well. Brian Lumley cites the importance of Derleth to his own Lovecraftian work, and contends in a 2009 introduction to Derleth's work that he was "...one of the first, finest, and most discerning editors and publishers of macabre fiction."
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Important as was Derleth's work to rescue H.P. Lovecraft from literary obscurity at the time of Lovecraft's death, Derleth also built a body of horror and spectral fiction of his own; still frequently anthologized. The best of this work, recently reprinted in four volumes of short stories – most of which were originally published in "Weird Tales", illustrates Derleth's original abilities in the genre. While Derleth considered his work in this genre less important than his most serious literary efforts, the compilers of these four anthologies, including Ramsey Campbell, note that the stories still resonate after more than 50 years.
In 2009, The Library of America selected Derleth's story "The Panelled Room" for inclusion in its two-century retrospective of American Fantastic Tales.
Other works.
Derleth also wrote many historical novels, as part of both the "Sac Prairie Saga" and the "Wisconsin Saga". He also wrote history; arguably most notable among these was "The Wisconsin: River of a Thousand Isles", published in 1942. The work was one in a series entitled "The Rivers of America", conceived by writer Constance Lindsay Skinner during the Great Depression as a series that would connect Americans to their heritage through the history of the great rivers of the nation. Skinner wanted the series to be written by artists, not academicians. Derleth, while not a trained historian, was, according to former Wisconsin state historian William F. Thompson, "...a very competent regional historian who based his historical writing upon research in the primary documents and who regularly sought the help of professionals... ." In the foreword to the 1985 reissue of the work by The University of Wisconsin Press, Thompson concluded: "No other writer, of whatever background or training, knew and understood his particular 'corner of the earth' better than August Derleth."
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Additionally, Derleth wrote a number of volumes of poetry. Three of his collections – "Rind of Earth" (1942), "Selected Poems" (1944), and "The Edge of Night" (1945) – were published by the Decker Press, which also printed the work of other Midwestern poets such as Edgar Lee Masters.
Derleth was also the author of several biographies of other writers, including Zona Gale, Ralph Waldo Emerson and Henry David Thoreau.
He also wrote introductions to several collections of classic early 20th century comics, such as "Buster Brown", "Little Nemo in Slumberland", and "Katzenjammer Kids", as well as a book of children's poetry entitled "A Boy's Way", and the foreword to "Tales from an Indian Lodge" by Phebe Jewell Nichols"." Derleth also wrote under the pen names Stephen Grendon, Kenyon Holmes and Tally Mason.
Derleth's papers were donated to the Wisconsin Historical Society in Madison.
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Alps
The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia.
The Alpine arch extends from Nice on the western Mediterranean to Trieste on the Adriatic and Vienna at the beginning of the Pannonian Basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn.
Mont Blanc spans the French–Italian border, and at is the highest mountain in the Alps. The Alpine region area contains 82 peaks higher than .
The altitude and size of the range affect the climate in Europe; in the mountains, precipitation levels vary greatly and climatic conditions consist of distinct zones. Wildlife such as ibex live in the higher peaks to elevations of , and plants such as edelweiss grow in rocky areas in lower elevations as well as in higher elevations.
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Evidence of human habitation in the Alps goes back to the Palaeolithic era. A mummified man ("Ötzi"), determined to be 5,000 years old, was discovered on a glacier at the Austrian–Italian border in 1991.
By the 6th century BC, the Celtic La Tène culture was well established. Hannibal notably crossed the Alps with a herd of elephants, and the Romans had settlements in the region. In 1800, Napoleon crossed one of the mountain passes with an army of 40,000. The 18th and 19th centuries saw an influx of naturalists, writers, and artists, in particular, the Romanticists, followed by the golden age of alpinism as mountaineers began to ascend the peaks of the Alps.
The Alpine region has a strong cultural identity. Traditional practices such as farming, cheesemaking, and woodworking still thrive in Alpine villages. However, the tourist industry began to grow early in the 20th century and expanded significantly after World War II, eventually becoming the dominant industry by the end of the century.
The Winter Olympic Games have been hosted in the Swiss, French, Italian, Austrian and German Alps. the region is home to 14 million people and has 120 million annual visitors.
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Etymology and toponymy.
The English word "Alps" comes from the Latin "Alpes".
The Latin word "Alpes" could possibly come from the adjective "albus" ("white"), or could possibly come from the Greek goddess Alphito, whose name is related to "alphita", the "white flour"; "alphos", a dull white leprosy; and finally the Proto-Indo-European word *albʰós. Similarly, the river god Alpheus is also supposed to derive from the Greek "alphos" and means whitish.
In his commentary on the "Aeneid" of Virgil, the late fourth-century grammarian Maurus Servius Honoratus says that all high mountains are called "Alpes" by Celts.
According to the "Oxford English Dictionary", the Latin "Alpes" might derive from a pre-Indo-European word *"alb" "hill"; "Albania" is a related derivation. Albania, the name of the region known as the country of Albania, has been used as a name for several mountainous areas across Europe.
In Roman times, "Albania" was a name for the eastern Caucasus, while in the English languages "Albania" (or "Albany") was occasionally used as a name for Scotland, although it is more likely derived from the Latin word "albus", the colour white.
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In modern languages the term "alp", "alm", "albe" or "alpe" refers to a grazing pastures in the alpine regions below the glaciers, not the peaks.
An "alp" refers to a high mountain pasture, typically near or above the tree line, where cows and other livestock are taken to be grazed during the summer months and where huts and hay barns can be found, sometimes constituting tiny hamlets. Therefore, the term "the Alps", as a reference to the mountains, is a misnomer. The term for the mountain peaks varies by nation and language: words such as "Horn", "Kogel", "Kopf", "Gipfel", "Spitze", "Stock", and "Berg" are used in German-speaking regions; "Mont", "Pic", "Tête", "Pointe", "Dent", "Roche", and "Aiguille" in French-speaking regions; and "Monte", "Picco", "Corno", "Punta", "Pizzo", or "Cima" in Italian-speaking regions.
Geography.
The Alps are a crescent shaped geographic feature of central Europe that ranges in an arc (curved line) from east to west and is in width. The mean height of the mountain peaks is . The range stretches from the Mediterranean Sea north above the Po basin, extending through France from Grenoble, and stretching eastward through mid and southern Switzerland. The range continues onward toward Vienna, Austria, and southeast to the Adriatic Sea and Slovenia.
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To the south it dips into northern Italy and to the north extends to the southern border of Bavaria in Germany. In areas like Chiasso, Switzerland, and Allgäu, Bavaria, the demarcation between the mountain range and the flatlands are clear; in other places such as Geneva, the demarcation is less clear.
The Alps are found in the following countries: Austria (28.7% of the range's area), Italy (27.2%), France (21.4%), Switzerland (13.2%), Germany (5.8%), Slovenia (3.6%), Liechtenstein (0.08%) and Monaco (0.001%).
The highest portion of the range is divided by the glacial trough of the Rhône valley, from Mont Blanc to the Matterhorn and Monte Rosa on the southern side, and the Bernese Alps on the northern. The peaks in the easterly portion of the range, in Austria and Slovenia, are smaller than those in the central and western portions.
The variances in nomenclature in the region spanned by the Alps make classification of the mountains and subregions difficult, but a general classification is that of the Eastern Alps and Western Alps with the divide between the two occurring in eastern Switzerland according to geologist Stefan Schmid, near the Splügen Pass.
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The highest peaks of the Western Alps and Eastern Alps, respectively, are Mont Blanc, at , and Piz Bernina, at . The second-highest major peaks are Monte Rosa, at , and Ortler, at , respectively.
A series of lower mountain ranges run parallel to the main chain of the Alps, including the French Prealps in France and the Jura Mountains in Switzerland and France. The secondary chain of the Alps follows the watershed from the Mediterranean Sea to the Wienerwald, passing over many of the highest and most well-known peaks in the Alps. From the Colle di Cadibona to Col de Tende it runs westwards, before turning to the northwest and then, near the Colle della Maddalena, to the north. Upon reaching the Swiss border, the line of the main chain heads approximately east-northeast, a heading it follows until its end near Vienna.
The northeast end of the Alpine arc, directly on the Danube, which flows into the Black Sea, is the Leopoldsberg near Vienna. In contrast, the southeastern part of the Alps ends on the Adriatic Sea in the area around Trieste towards Duino and Barcola.
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Passes.
The Alps have been crossed for war and commerce, and by pilgrims, students, and tourists. Crossing routes by road, train, or foot are known as "passes", and usually consist of depressions in the mountains in which a valley leads from the plains and hilly pre-mountainous zones. Merchant traffic was supported by pack animals such as mules. In the late Middle Ages heavy carts and sleighs were in use on the alpine passes.
In the medieval period hospices were established by religious orders at the summits of many of the main passes. The most important passes are the Col de l'Iseran (the highest), the Col Agnel, the Brenner Pass, the Mont-Cenis, the Great St. Bernard Pass, the Col de Tende, the Gotthard Pass, the Semmering Pass, the Simplon Pass, and the Stelvio Pass.
Crossing the Italian-Austrian border, the Brenner Pass separates the Ötztal Alps and Zillertal Alps and has been in use as a trading route since the 14th century. The lowest of the Alpine passes at is the Semmering crossing from Lower Austria to Styria. It has been in continuous use since the 12th century when a hospice was built there. A railroad with a tunnel long was built along the route of the pass in the mid-19th century. With a summit of , the Great St Bernard Pass is one of the highest in the Alps, crossing the Italian-Swiss border east of the Pennine Alps along the flanks of Mont Blanc. The pass was used by Napoleon Bonaparte to cross 40,000 troops in 1800.
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The Mont Cenis pass has been a major commercial and military road between Western Europe and Italy. The pass was crossed by many troops on their way to the Italian peninsula. From Constantine I, Pepin the Short and Charlemagne to Henry IV, Napoléon and more recently the German Gebirgsjägers during World War II.
In the 18th century the principal passes of the Alps were modernized by engineers to speed up passenger and freight transport. The Mont Cenis pass has been supplanted by the Fréjus Rail Tunnel opening in 1871, while the Fréjus Road Tunnel opened 1980. Railway lines could not be built in the Alps without tunnels and bridges. Apart from the Mont Cenis railway tunnel the Semmering railway tunnel and the Gotthard railway tunnel were built between 1854 and 1882. By the early 19th century eight trans-alpine railway lines had been put into operation.
The Saint Gotthard Pass crosses from Central Switzerland to Ticino. In 1882 the Saint Gotthard Railway Tunnel was opened connecting Lucerne in Switzerland, with Milan in Italy. 98 years later followed Gotthard Road Tunnel ( long) connecting the A2 motorway in Göschenen on the north side with Airolo on the south side, exactly like the railway tunnel.
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On 1 June 2016 the world's longest railway tunnel, the Gotthard Base Tunnel, was opened, which connects Erstfeld in canton of Uri with Bodio in canton of Ticino by two single tubes of .
It is the first tunnel that traverses the Alps on a flat route.
From 11 December 2016, it has been part of the regular railway timetable and used hourly as standard ride between Basel/Lucerne/Zurich and Bellinzona/Lugano/Milan.
The highest pass in the alps is the Col de l'Iseran in Savoy (France) at , followed by the Stelvio Pass in northern Italy at ; the road was built in the 1820s.
Highest mountains.
The Union Internationale des Associations d'Alpinisme (UIAA) has defined a list of 82 "official" Alpine summits that reach at least . The list includes not only mountains, but also subpeaks with little prominence that are considered important mountaineering objectives. Below are listed the 29 "four-thousanders" with at least of prominence.
While Mont Blanc was first climbed in 1786 and the Jungfrau in 1811, most of the Alpine four-thousanders were climbed during the second half of the 19th century, notably Piz Bernina (1850), the Dom (1858), the Grand Combin (1859), the Weisshorn (1861) and the Barre des Écrins (1864); the ascent of the Matterhorn in 1865 marked the end of the golden age of alpinism. Karl Blodig (1859–1956) was among the first to successfully climb all the major 4,000 m peaks. He completed his series of ascents in 1911. Many of the big Alpine three-thousanders were climbed in the early 19th century, notably the Grossglockner (1800) and the Ortler (1804), although some of them were climbed only much later, such at Mont Pelvoux (1848), Monte Viso (1861) and La Meije (1877).
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The first British Mont Blanc ascent by a man was in 1788; the first ascent by a woman was in 1808. By the mid-1850s Swiss mountaineers had ascended most of the peaks and were eagerly sought as mountain guides. Edward Whymper reached the top of the Matterhorn in 1865 (after seven attempts), and in 1938 the last of the six great north faces of the Alps was climbed with the first ascent of the Eiger "Nordwand" (north face of the Eiger).
Geology and orogeny.
Important geological concepts were established as naturalists began studying the rock formations of the Alps in the 18th century. In the mid-19th century, the now-defunct idea of geosynclines was used to explain the presence of "folded" mountain chains. This theory was replaced in the mid-20th century by the theory of plate tectonics.
The formation of the Alps (the Alpine orogeny) was an episodic process that began about 300 million years ago. In the Paleozoic Era the Pangaean supercontinent consisted of a single tectonic plate; it broke into separate plates during the Mesozoic Era and the Tethys sea developed between Laurasia and Gondwana during the Jurassic Period. The Tethys was later squeezed between colliding plates causing the formation of mountain ranges called the Alpide belt, from Gibraltar through the Himalayas to Indonesia—a process that began at the end of the Mesozoic and continues into the present. The formation of the Alps was a segment of this orogenic process, caused by the collision between the African and the Eurasian plates that began in the late Cretaceous Period.
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Under extreme compressive stresses and pressure, marine sedimentary rocks were uplifted, forming characteristic recumbent folds, and thrust faults. As the rising peaks underwent erosion, a layer of marine flysch sediments was deposited in the foreland basin, and the sediments became involved in younger folds as the orogeny progressed. Coarse sediments from the continual uplift and erosion were later deposited in foreland areas north of the Alps. These regions in Switzerland and Bavaria are well-developed, containing classic examples of flysch, which is sedimentary rock formed during mountain building.
The Alpine orogeny occurred in ongoing cycles through to the Paleogene causing differences in folded structures, with a late-stage orogeny causing the development of the Jura Mountains. A series of tectonic events in the Triassic, Jurassic and Cretaceous periods caused different paleogeographic regions. The Alps are subdivided by different lithology (rock composition) and nappe structures according to the orogenic events that affected them. The geological subdivision differentiates the Western, Eastern Alps, and Southern Alps: the Helveticum in the north, the Penninicum and Austroalpine system in the centre and, south of the Periadriatic Seam, the Southern Alpine system.
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According to geologist Stefan Schmid, because the Western Alps underwent a metamorphic event in the Cenozoic Era while the Austroalpine peaks underwent an event in the Cretaceous Period, the two areas show distinct differences in nappe formations. Flysch deposits in the Southern Alps of Lombardy probably occurred in the Cretaceous or later.
Peaks in France, Italy and Switzerland lie in the "Houillière zone", which consists of basement with sediments from the Mesozoic Era. High "massifs" with external sedimentary cover are more common in the Western Alps and were affected by Neogene Period thin-skinned thrusting whereas the Eastern Alps have comparatively few high peaked massifs. Similarly the peaks in eastern Switzerland extending to western Austria (Helvetic nappes) consist of thin-skinned sedimentary folding that detached from former basement rock.
In simple terms, the structure of the Alps consists of layers of rock of European, African, and oceanic (Tethyan) origin. The bottom nappe structure is of continental European origin, above which are stacked marine sediment nappes, topped off by nappes derived from the African plate. The Matterhorn is an example of the ongoing orogeny and shows evidence of great folding. The tip of the mountain consists of gneisses from the African plate; the base of the peak, below the glaciated area, consists of European basement rock. The sequence of Tethyan marine sediments and their oceanic basement is sandwiched between rock derived from the African and European plates.
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The core regions of the Alpine orogenic belt have been folded and fractured in such a manner that erosion produced the characteristic steep vertical peaks of the Swiss Alps that rise seemingly straight out of the foreland areas. Peaks such as Mont Blanc, the Matterhorn, and high peaks in the Pennine Alps, the Briançonnais, and Hohe Tauern consist of layers of rock from the various orogenies including exposures of basement rock.
Due to the ever-present geologic instability, earthquakes continue in the Alps to this day. Typically, the largest earthquakes in the alps have been between magnitude 6 and 7 on the Richter scale. Geodetic measurements show ongoing topographic uplift at rates of up to about 2.5 mm per year in the North, Western and Central Alps, and at ~1 mm per year in the Eastern and South-Western Alps. The underlying mechanisms that jointly drive the present-day uplift pattern are the isostatic rebound due to the melting of the last glacial maximum ice-cap or long-term erosion, detachment of the Western Alpine subducting slab, mantle convection as well as ongoing horizontal convergence between Africa and Europe, but their relative contributions to the uplift of the Alps are difficult to quantify and likely to vary significantly in space and time.
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Minerals.
The Alps are a source of minerals that have been mined for thousands of years. In the 8th to 6th centuries, BC during the Hallstatt culture, Celtic tribes mined copper; later the Romans mined gold for coins in the Bad Gastein area. Erzberg in Styria furnishes high-quality iron ore for the steel industry. Crystals, such as cinnabar, amethyst, and quartz, are found throughout much of the Alpine region. The cinnabar deposits in Slovenia are a notable source of cinnabar pigments.
Alpine crystals have been studied and collected for hundreds of years and began to be classified in the 18th century. Leonhard Euler studied the shapes of crystals, and by the 19th-century crystal hunting was common in Alpine regions. David Friedrich Wiser amassed a collection of 8000 crystals that he studied and documented. In the 20th century Robert Parker wrote a well-known work about the rock crystals of the Swiss Alps; at the same period a commission was established to control and standardize the naming of Alpine minerals.
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Glaciers.
In the Miocene Epoch the mountains underwent severe erosion because of glaciation, which was noted in the mid-19th century by naturalist Louis Agassiz who presented a paper proclaiming the Alps were covered in ice at various intervals—a theory he formed when studying rocks near his Neuchâtel home which he believed originated to the west in the Bernese Oberland. Because of his work he came to be known as the "father of the ice-age concept" although other naturalists before him put forth similar ideas.
Agassiz studied glacier movement in the 1840s at the Unteraar Glacier where he found the glacier moved per year, more rapidly in the middle than at the edges. His work was continued by other scientists and now a permanent laboratory exists inside a glacier under the Jungfraujoch, devoted exclusively to the study of Alpine glaciers.
Glaciers pick up rocks and sediment with them as they flow. This causes erosion and the formation of valleys over time. The Inn valley is an example of a valley carved by glaciers during the ice ages with a typical terraced structure caused by erosion. Eroded rocks from the most recent ice age lie at the bottom of the valley while the top of the valley consists of erosion from earlier ice ages. Glacial valleys have characteristically steep walls (reliefs); valleys with lower reliefs and talus slopes are remnants of glacial troughs or previously infilled valleys. Moraines, piles of rock picked up during the movement of the glacier, accumulate at edges, centre, and the terminus of glaciers.
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Alpine glaciers can be straight rivers of ice, long sweeping rivers, spread in a fan-like shape (Piedmont glaciers), and curtains of ice that hang from vertical slopes of the mountain peaks. The stress of the movement causes the ice to break and crack loudly, perhaps explaining why the mountains were believed to be home to dragons in the medieval period. The cracking creates unpredictable and dangerous crevasses, often invisible under new snowfall, which causes the greatest danger to mountaineers.
Glaciers end in ice caves (the Rhône Glacier), by trailing into a lake or river, or by shedding snowmelt on a meadow. Sometimes a piece of glacier will detach or break resulting in flooding, property damage, and loss of life.
High levels of precipitation cause the glaciers to descend to permafrost levels in some areas whereas in other, more arid regions, glaciers remain above about the level. The of the Alps covered by glaciers in 1876 had shrunk to by 1973, resulting in decreased river run-off levels. Forty percent of the glaciation in Austria has disappeared since 1850, and 30% of that in Switzerland.
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Although the Alpine topography shows marked glacial morphologies, the mechanisms by which glacial reshaping occurs are unclear. Numerical modeling suggests that glacial erosion propagates from low elevations to high elevations leading to an early increase of local relief followed by lowering of the mean orogen elevation.
Rivers and lakes.
The Alps provide lowland Europe with drinking water, irrigation, and hydroelectric power. Although the area is only about 11% of the surface area of Europe, the Alps provide up to 90% of water to lowland Europe, particularly to arid areas and during the summer months. Cities such as Milan depend on 80% of water from Alpine runoff. Water from the rivers is used in at least 550 hydroelectricity power plants, considering only those producing at least 10MW of electricity.
Major European rivers flow from the Alps, such as the Rhine, the Rhône, the Inn, and the Po, all of which have headwaters in the Alps and flow into neighbouring countries, finally emptying into the North Sea, the Mediterranean Sea, the Adriatic Sea and the Black Sea. Other rivers such as the Danube have major tributaries flowing into them that originate in the Alps.
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The Rhône is second to the Nile as a freshwater source to the Mediterranean Sea; the river begins as glacial meltwater, flows into Lake Geneva, and from there to France where one of its uses is to cool nuclear power plants. The Rhine originates in a area in Switzerland and represents almost 60% of water exported from the country. Tributary valleys, some of which are complicated, channel water to the main valleys which can experience flooding during the snowmelt season when rapid runoff causes debris torrents and swollen rivers.
The rivers form lakes, such as Lake Geneva, a crescent-shaped lake crossing the Swiss border with Lausanne on the Swiss side and the town of Evian-les-Bains on the French side. In Germany, the medieval St. Bartholomew's chapel was built on the south side of the Königssee, accessible only by boat or by climbing over the abutting peaks.
Additionally, the Alps have led to the creation of large lakes in Italy. For instance, the Sarca, the primary inflow of Lake Garda, originates in the Italian Alps. The Italian Lakes are a popular tourist destination since the Roman Era for their mild climate.
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Scientists have been studying the impact of climate change and water use. For example, each year more water is diverted from rivers for snowmaking in the ski resorts, the effect of which is yet unknown. Furthermore, the decrease of glaciated areas combined with a succession of winters with lower-than-expected precipitation may have a future impact on the rivers in the Alps as well as an effect on the water availability to the lowlands.
Climate.
The Alps are a classic example of what happens when a temperate area at lower altitude gives way to higher-elevation terrain. Elevations around the world that have cold climates similar to those of the polar regions have been called Alpine. A rise from sea level into the upper regions of the atmosphere causes the temperature to decrease (see adiabatic lapse rate). The effect of mountain chains on prevailing winds is to carry warm air belonging to the lower region into an upper zone, where it expands in volume at the cost of a proportionate loss of temperature, often accompanied by precipitation in the form of snow or rain. The height of the Alps is sufficient to divide the weather patterns in Europe into a wet north and dry south because moisture is sucked from the air as it flows over the high peaks.
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The severe weather in the Alps has been studied since the 18th century; particularly the weather patterns such as the seasonal foehn wind. Numerous weather stations were placed in the mountains early in the early 20th century, providing continuous data for climatologists. Some of the valleys are quite arid such as the Aosta Valley in Italy, the Maurienne in France, the Valais in Switzerland, and northern Tyrol.
The areas that are not arid and receive high precipitation experience periodic flooding from rapid snowmelt and runoff. The mean precipitation in the Alps ranges from a low of per year to per year, with the higher levels occurring at high altitudes. At altitudes between , snowfall begins in November and accumulates through to April or May when the melt begins. Snow lines vary from , above which the snow is permanent and the temperatures hover around the freezing point even during July and August. High-water levels in streams and rivers peak in June and July when the snow is still melting at the higher altitudes.
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