On the Scratched Boulders and Rocks of the Coal-field of Scotland.

Abstract

The phænomenon of scratched boulders has of late attracted attention from its supposed connexion with glacial action; but before the researches of Professor Agassiz had excited so much interest on the subject, it had been but little attended to. When he visited Scotland in 1840, with the object of searching for proofs of the former existence of glaciers in that country, and their connexion with the erratic blocks and the so-called diluvium or till, his attention was immediately arrested by the striæ which were observed upon some of the blocks. He however admitted to me then, as he has since done in his paper on the subject, that the deposit in which these boulders occurred “was not produced by true glaciers, although intimately connected with the phænomena of ice.” He also states, in the above-quoted paper, that “the erratic blocks in Switzerland are always angular,” which is just what might have been expected if they were transported by ice, whether upon glaciers or icebergs. The erratic blocks in Scotland, on the other hand, are rounded, and we have two problems to solve,—how have they been rounded? and how have they been scratched? Before attempting to answer these questions, it is necessary that we should be made acquainted with all the circumstances under which these blocks are found; we can then compare the facts with proposed solutions, and by excluding those which are inconsistent with well-established facts, be driven at last to that solution which explains them all. Every person has