A letter concerning deep-sea dredgings, addressed to Professor Benjamin Peirce, Superintendent United States Coast Survey / by Louis Agassiz.

Date:
[1871?]
Catalogue details

Licence: Public Domain Mark

Credit: A letter concerning deep-sea dredgings, addressed to Professor Benjamin Peirce, Superintendent United States Coast Survey / by Louis Agassiz. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    But, there is a subject of great interest likely to be elucidated by our investigation, — the contrast of the deep-sea faunae of the northern with those of the southern hemisphere. Judging from what Australia has already brought us, w.e may expect to find that the animal world of the southern hemisphere has a more antique character, in the same way as North America may be contrasted with Europe, on the ground of the occurrence in the United States of animals and plants now living here, the types of which are only found fossil in Europe. A few more words, upon another subject. During the first three decades of this century, the scientific world believed that the erratic boulders, which form so prominent a feature of the surface geology of Europe, had been transported by currents arising from the rupture of the barriers of great lakes among the Alps, or started from the north by earthquake waves. Shepherds first started the idea- that within the valleys of Switzer- land these huge boulders had been carried forward by glaciers, and Swiss geologists, Yenetz and Charpentier foremost among them, very soon proved that this had been the case. This view, however, remained confined to the vicinity of the Alps in its application, until I suggested that the phenomenon might have a Cosmic importance, which was proved when I discovered, in 1840, unmistakable traces of glaciers in Scotland, England, and Ireland, in regions which could have had no connection whatever with the elevation of the Alps. Since that time the glacial -period has been considered by geologists as a fixed fact, whatever may have been the discrepancies among them as to the ex- tent of these continental masses of ice, their origin, and their mode of action. There is, however, one kind of evidence wanting to remove every possible doubt that the greater extension of glaciers in former ages was connected with cosmic changes in the physical condition of our globe. All the phenomena related to the glacial period must be found in the southern hemisphere with the same characteristic features as in the north, with this essential difference, that everything must be reversed; that is, the trend of the glacial abrasion must be from the south north- ward i the lee side of abraded rocks must be on the north side of hills and mountain ranges, and the boulders must have been derived from rocky exposures lying to the south of their present position. Whether this is so or not has not yet been ascertained by direct observation. I