About the year 1837 Agassiz had been led by his investigation of the boulder-clay of Switzerland to the conclusion that at one time the glaciers had extended far beyond their present limits, and had covered the plains at the foot of the Alps with a vast confluent sheet of ice. Agassiz, in 1840, visited Scotland with Dean Buckland, and as the result of his observations had not hesitated to declare that Scotland also had been swathed in an ice-sheet. British geologists, however, were slow to accept his conclusions, and the favourite explanation of the “drifts” was that they had been laid down at the bottom of a sea in which icebergs floated, transporting great rock boulders from one place to another. In 1866 the veteran geologist Charles Maclaren, then at the age of eighty-four, published the second edition of his _Geology of Fife and the Lothians_, and in his account of the “alluvial phenomena” of the district he shows the transitional state in which opinion then was passing from the iceberg hypothesis to the land-ice hypothesis. “The dressed surfaces as well as the ‘Till’ or Diluvium [the lower boulder-clay] seem to have been mainly due to a great envelope of ice acting for ages; the newer alluvium, on the other hand [the upper boulder-clay], appears to have been chiefly due to icebergs and ocean currents. In thus attributing so much to the action of ice during a long glacial period, it must ever be borne in mind that oceanic currents preceded this ice action, and that similar currents must have been in existence to transport the icebergs to which we ascribe the erratic blocks and boulders. Alternate submergence and elevation of the north of Europe, combined with ice on land and ice on water (in my opinion), must satisfactorily explain these diluvial phenomena, which, as unsettled problems, are still engaging the attention of younger geologists.” One of the ablest champions of the land-ice hypothesis was Robert Chambers, who was widely known as a historian and a member of the famous Edinburgh publishing firm. As early as 1852 he ranged himself on the side of Agassiz, declaring that floating icebergs and currents of water could not possibly be accepted as a satisfactory explanation of the boulder-clay and striated rock-surfaces. Mr T. F. Jamieson of Ellon was making a very careful study of the drifts of Aberdeenshire and the adjacent counties, and had little hesitation in accepting the theory of an extensive ice-sheet, covering these districts and filling up all the valleys, as the explanation most in accordance with the facts which he had observed. He admitted, however, that subsequently there had been a great submergence during which many of the uppermost drift deposits had been laid down.