Editing Louis Agassiz (section)

==Ice age==
[[File:Agassiz, Louis – Nouvelles études et expériences sur les glaciers actuels, 1847 – BEIC 12025435.jpg|thumb|upright|''Nouvelles études et expériences sur les glaciers actuels'', 1847]]

The vacation of 1836 was spent by Agassiz and his wife in the little village of [[Bex]], where he met [[Jean de Charpentier]] and [[Ignaz Venetz]]. Their recently announced [[Ice_age#History_of_research|glacial theories]] had startled the scientific world, and Agassiz returned to Neuchâtel as an enthusiastic convert.<ref name="BDA1906p62">{{harvnb|Johnson|1906|p=62}}</ref> In 1837, Agassiz proposed that the Earth had been subjected to a past [[ice age]].<ref name="evans 1887">E.P. Evans: "The Authorship of the Glacial Theory", ''North American review'' Volume 145, Issue 368, July 1887. Accessed on January 24, 2018. {{jstor|25101263}}</ref> He presented the theory to the [[Helvetic Society]] that ancient glaciers flowed outward from the Alps, and even larger glaciers had covered the plains and mountains of Europe, Asia, and North America and smothered the entire [[Northern Hemisphere]] in a prolonged ice age. In the same year, he was elected a foreign member of the [[Royal Swedish Academy of Sciences]]. Before that proposal, [[Johann Wolfgang von Goethe|Goethe]], [[Horace-Bénédict de Saussure|de Saussure]], Ignaz Venetz, Jean de Charpentier, [[Karl Friedrich Schimper]], and others had studied the [[glaciers]] of the Alps, and Goethe,<ref name="goethe">{{cite book |last=Cameron |first=Dorothy |year=1964 |title=Early discoverers XXII, Goethe-Discoverer of the ice age. Journal of glaciology |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/7883A16803630B43E40A1364C62EEBD7/S0022143000018761a.pdf/div-class-title-early-discoverers-xxii-goethe-discoverer-of-the-ice-age-div.pdf |access-date=September 10, 2023 |archive-date=July 28, 2018 |archive-url=https://web.archive.org/web/20180728091738/https://www.cambridge.org/core/services/aop-cambridge-core/content/view/7883A16803630B43E40A1364C62EEBD7/S0022143000018761a.pdf/div-class-title-early-discoverers-xxii-goethe-discoverer-of-the-ice-age-div.pdf |url-status=bot: unknown }}</ref> Charpentier, and Schimper<ref name="evans 1887" /> had even concluded that the [[glacial erratic|erratic]] blocks of alpine rocks scattered over the slopes and summits of the [[Jura Mountains]] had been moved there by glaciers. Those ideas attracted the attention of Agassiz, and he discussed them with Charpentier and Schimper, whom he accompanied on successive trips to the Alps. Agassiz even had a hut constructed upon one of the [[Aar Glaciers]] and for a time made it his home to investigate the structure and movements of the ice.{{sfn|Woodward|1911|p=367}}

Agassiz visited England, and with [[William Buckland]], the only English naturalist who shared his ideas, made a tour of the [[British Isles]] in search of glacial phenomena, and became satisfied that his theory of an ice age was correct.<ref name="BDA1906p62" /> In 1840, Agassiz published a two-volume work, ''Études sur les glaciers'' ("Studies on Glaciers").<ref>[http://fr.wikisource.org/w/index.php?title=%C3%89tudes_sur_les_glaciers&oldid=297457 Louis Agassiz: ''Études sur les glaciers'', Neuchâtel 1840. Digital book on Wikisource]. Accessed on February 25, 2008.</ref> In it, he discussed the movements of the glaciers, their [[moraines]], and their influence in grooving and rounding the rocks and in producing the striations and ''roches moutonnées'' seen in Alpine-style landscapes. He accepted Charpentier and Schimper's idea that some of the alpine glaciers had extended across the wide plains and valleys of the [[Aar]] and [[Rhône]], but he went further by concluding that in the recent past, Switzerland had been covered with one vast sheet of ice originating in the higher Alps and extending over the valley of northwestern Switzerland to the southern slopes of the Jura. The publication of the work gave fresh impetus to the study of glacial phenomena in all parts of the world.{{sfn|Woodward|1911|pp=367–368}}

Familiar then with recent glaciation, Agassiz and the English geologist William Buckland visited the mountains of Scotland in 1840. There, they found clear evidence in different locations of glacial action. The discovery was announced to the Geological Society of London in successive communications. The mountainous districts of England, [[Wales]], and [[Ireland]] were understood to have been centres for the dispersion of glacial debris. Agassiz remarked "that great sheets of ice, resembling those now existing in [[Greenland]], once covered all the countries in which unstratified gravel (boulder drift) is found; that this gravel was in general produced by the [[trituration]] of the sheets of ice upon the subjacent surface, etc."{{sfn|Woodward|1911|p=368}}
[[File:SAM PC 0 - Ice auger of Louis Agassiz and Eduard Desor.jpg|thumb|upright=0.4|The man-sized iron [[auger (drill)|auger]] that was used by Agassiz to drill up to 7.5 m deep into the [[Unteraar Glacier]] to take its temperature ([[Swiss Alpine Museum]], Bern)]]

In his later years, Agassiz applied his glacial theories to the geology of the Brazilian tropics, including the Amazon. Agassiz began with a working hypothesis which could be tested by the results of fieldwork to find either inconclusive, or conclusively supporting or refuting evidence. A hypothesis that can be conclusively refuted is better than a hypothesis that is difficult to test. Agassiz had a close association with his student and field assistant, the geologist [[Charles Frederick Hartt|Charles Hartt]] who eventually refuted Agassiz's theories about the Amazon based on his fieldwork there. Instead of evidence for any glacial processes, he found chemically weathered sediments from marine and tropical fluvial, not glacial, processes, a finding that later geologists confirmed.<ref>Brice, W. R. and Silvia F. de M. Figueiroa 2001 Charles Hartt, Louis Agassiz, and the controversy over Pleistocene glaciation in Brazil. History of Science 39(2): 161–184.
</ref> Agassiz hypothesis that the Amazon was affected by the [[Last Glacial Maximum]] was correct, although the mechanism causing the effect was non-glacial. The Amazon rainforest was split into two large blocks by extensive savanna during the LGM.