138 Charles Maclaren, Esq., on the Existence of 



it rests. A current of water, if able to move it, would have 

 left it in the low country. And even were all Scotland con- 

 verted into a mer de glace, like Greenland, no moving mass^ 

 in the shape of a glacier could carry this boulder (and there 

 are many such) from its native seat in Perthshire or Argyle- 

 shire to Habbies How. An icebeg starting from the West 

 or North Highlands, and floating in a sea 1500 or 2000 feet 

 above the present level of the Atlantic, is an agent perfectly 

 capable of effecting the transportation of the stone, and offers^ 

 I think, the only conceivable solution of the difficulty. With 

 regard to the causes which produced the glaciers and ice- 

 bergs, it is now generally admitted by geologists, that at the 

 period when the boulder clay was deposited, Scotland and 

 several other countries had a much colder climate than they 

 have at present — a climate probably similar to that of Ice- 

 land* 



The anomalous presence of granite boulders at Gare Loch 

 seems best explained by assuming that they were floated on. 

 icebergs from Ben Cruachen, Ben Nevis, or some other of 

 the lofty granite mountains of the north. The sea must then 

 have stood perhaps 1500 feet above its present level, to per- 

 mit the rafts of ice to pass over the lowest part of the bar- 

 rier ; for we can scarcely suppose that they would thread 

 their way through the narrow and intricate valleys which in- 

 tersect the group of mountains. I made a journey to Ben 

 Cruachen for the purpose of comparing the granite of that 

 hill with the boulders at Gare Loch, but the rocks did not 

 agree. The general aspect was much the same, but the em- 

 bedded crystals of felspar, common to most of the boulders, 

 were altogether wanting in the granite of the hill, so far as 

 I was able to examine it ; and I had not leisure to visit the 

 three northern mountains of the great granitic group to which 

 Ben Cruachen belongs. 



Though glaciers are the only bodies that are known to 

 groove and furrow the rocks in the manner described, it ia 



* The agency of icebergs in transporting rocks is admirably explained 

 by Lyell. {Elements^ chap, x.) On the former existence of an arctio- 

 climate here, see chap. xi. of the same work. 



