The History of the European Fauna (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...also in the occasional occurrence of sea-shells, the frequent appearance of bedded deposits, and the often inexplicable course taken by boulders from their source of origin. There occurs often a singular mixture and an apparent crossing of the paths of boulders in the boulderclay. Professor Bonney remarks (p. 280) that these are less difficult to explain on the hypothesis of distribution by floating ice than on that of transport by land-ice, because, in the former case, though the drift of winds and currents would be generally in one direction, both might be varied at particular seasons. So far as concerns the distribution and thickness of the glacial deposits, he says there is not much to choose between either hypothesis; but on that of land-ice it is extremely difficult to explain the intercalation of perfectly stratified sands and gravels and of boulder-clay, as well as the not infrequent signs of bedding in the latter. Two divisions are generally recognisable in the continental boulder-clay--a lower and an upper. An inter-glacial phase characterised by a less severe climate is assumed to have intervened between the deposition of the two. In Russia no such division can as a rule be made out, and sea-shells are either entirely absent or extremely scarce. It has been pointed out by Professor J. Geikie that the erratics--a name applied to boulders in boulder-clay--in the upper division have travelled in a different direction from those contained in the lower. Taking for granted that the boulderclay is a marine deposit, this phenomenon seems to indicate that the current which prevai'ied during the early part of the Glacial period in this North European ocean was different from the prevailing current during the latter part. I have attempted to explain this ci...