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



which agent must, therefore, have risen up from the rock about 3 feet, in order 

 to score the boulder.* 



If the foregoing enumeration of localities correctly represents the general 

 direction of the markings on the rocks, it is impossible to avoid the conclusion 

 that they have been made by one and the same agent, and over a very large area 

 of the earth's surface. How can it be conceived that glaciers should over that 

 large area have all moved in the same direction ? Objections to the glacier theory 

 are suggested even by cases of isolated boulders.f But the objections become 

 infinitely stronger, when it appears that over an area of North- Western Europe, 

 comprising Iceland, Faroe, Shetland, Scotland, Ireland, a great part of England, 

 and on some of the adjoining continental countries, the agent which affected the 

 boulder-clay, transporting blocks and striating rocks, moved almost everywhere 

 in nearly the same direction, and came chiefly from that quarter where there is 

 only the ocean. 



The late Principal Forbes, much as he was inclined to uphold the agency of 

 glaciers, felt the force of these objections, and makes the following confession in 

 his work on the Glaciers of Norway (p. 241): — " I hesitate to ascribe everything 

 to glaciers. In fact, there appears to me to be situations along the coast of 

 Norway, where the action of abrasion having been parallel with the coast, the 

 movement of a glacier would be inconceivable. The general parallelism of the 

 striae, observed by Bothlink and others, over a large area of country, not 

 coincident with the general fall of the ground, would seem, if confirmed, 

 to be equally inexplicable on the pure glacier hypothesis. The continuation 

 of the striae across table-lands, and over cols, is of the like ambiguous character. 

 I have never hesitated to express, on similar grounds, doubts as to the 

 universal application of the usual glacier theory to the phenomena of our 

 own islands, which, on a small scale, are the counterpart of those of Norway. 

 For, though perfectly satisfied that our hills were in former times the seat of 

 glaciers which even approached the sea-level, I find the utmost difficulty in 

 explaining, by such an hypothesis alone, the facts which occur even in the 

 immediate vicinity of Edinburgh." 



In another part of the same work, Principal Forbes threw out a surmise 

 of the kind of agent which seemed to him probable. Referring to the range of 

 hills on the west coast of Norway (p. 190), he says that these bore " the 

 whole brunt of forces which appear to have come from the north, and not only 



* Lond. Geolog. Journal for 1845, vol. i. p. 876. 



t Thus Mr Maclaren says — " I have pointed out a boulder of mica slate in the Pentland Hills, 

 weighing 8 or 10 tons, which must have come 50 miles at least. It lies on a steep acclivity 

 1000 feet above the sea ; and it must have passed over extensive tracts of country from 500 to 800 

 feet lower than the spot on which it rests. Even were all Scotland converted into a mer de glace, 

 like Greenland, no glacier could carry the boulder (and there are many such) from its parent rock, in 

 Perthshire or Argyleshire, to the Pentlands." — Select Writings, vol. ii. p. 115. 



