656 MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 



guished for accurate observation and cautious deduction, his discovery in Skye 

 added largely to the popularity of the glacier theory. The next quarter from 

 which light came was Wales, where Professor Ramsay recognised signs of ice 

 action. He was followed by Dr Chambers, the late Mr Maclaren, and Mr 

 Jameson of Ellon, who severally pointed out localities in many of the Scotch 

 counties. 



But whilst generally adopting and helping to illustrate this theory, almost all 

 of these geologists admitted that there were some phenomena of the boulder-clay 

 which could not be explained by any imaginable local glacier ; and they threw 

 out the idea that icebergs or icefloes, which it was discovered carried in the 

 Arctic and Antarctic regions enormous masses of rock and rubbish, might possibly 

 have in former times done similar work in North- Western Europe. 



By this time Agassiz himself appears to have become satisfied that many of 

 the ascertained facts could not be explained on the theory of glaciers flowing 

 down from isolated mountain ranges. Having gone to reside in America, he 

 obtained there an opportunity of studying the phenomena on a much larger scale 

 than either Switzerland or the whole of Northern Europe supplied, and was 

 greatly struck by seeing that boulders were scattered over an area of the earth's 

 surface, extending to nearly 1000 miles in every direction, and that these boulders 

 generally had all been transported from one quarter, viz., the north. Having 

 learnt, from the writings of Murchison and others, that the great mass of boulders 

 in Russia and Poland had also come from the north, and that in some cases the 

 parent rocks were more than 100 miles distant, he formally renounced the 

 theory of local glaciers, and propounded the notion that gigantic glaciers, more 

 than a mile in thickness, and derived from snow two or three miles deep, had 

 been generated in the Arctic regions, and were by some cause made to move over 

 the earth's surface towards the south, encasing great continents, filling sea-beds, 

 rising up slopes of land, overtopping mountains, and pushing before them, with 

 a colossal ice-foot, immense heaps of detritus. From his recent work on the 

 Brazils, it appears that this enthusiastic naturalist contends that the huge glacier 

 which passed over North America, reached even to the tropics.* 



I do not know or believe that this theory of Agassiz, in its full extent, has 

 been adopted by any geologist in either America or Europe ; but I am not sure 

 that it is not, to a modified extent, adopted by some of our Scotch geologists. 



Mr Geikie, in a very valuable paper on the " Glacial Drift of Scotland," says, 

 " that the ice existed, not as mere local glaciers descending the chief valleys, 

 but as one wide sheet covering the whole, or nearly the whole, country" (p. 78). 



* "Visit to the Brazils," p. 403. — Agassiz in this work contends for the existence of "a sheet 

 of snow 10,000 or 15,000 feet in thickness, extending all over the northern and southern portions 

 of the globe, — which in the end formed a northern and southern cap of ice moving towards the 

 equator ! " 



