MR DAVID MILNE HOME ON THE BOULDER- CLAY OF EUROPE. 679 



had the appearance of a gigantic causeway of boulders, caused apparently by 

 icebergs sliding over them, and levelling them.* 



It also deserves notice that true boulder-clay or till exists in the Arctic 

 regions, and in districts where there is much less probability of glaciers than of 

 icebergs having been at work. Sir John Richardson evidently describes this 

 deposit when he mentions " a tenacious and somewhat slaty blue clay, containing 

 many boulder- stones" on the western shores of Hudson's Bay, — a country very 

 little elevated above the sea, and possessing no mountains where glaciers could 

 be formed.f 



Nor is it irrelevant to notice the occurrence of boulder-clay in the Antarctic 

 regions, and the opinion formed by that eminent naturalist, Mr Darwin, as to its 

 origin. After describing " great masses of mud of a dark colour, full of boulders 

 of primitive rocks derived from mountains situated to the W. or S.W. about 

 60 miles distant," he says, that " the deposit in all respects resembles the till of 

 Scotland;" and adds, that "at present the oceanic currents off Cape Horn set 

 from the west ; so that if the ancient currents had the same direction, the 

 phenomena would be explained by floating ice."| 



It thus appears that both in Arctic and in the Antarctic regions, where float- 

 ing ice has abounded, boulder-clay, boulders, and polished rock surfaces exist. 

 These phenomena do not occur in warmer regions of the earth. Wherever the} r 

 do occur, there are indications of the sea having stood much higher than at 

 present, so that ice could have drifted at the necessary level; whilst, on the 

 other hand, in many districts there is a total want of the conditions necessary 

 for the formation and for the movement of glaciers in the required direction. 



8. In the previous part of this Memoir, I have attempted to show — 1st, 

 That glaciers were not the agents to which boulder-clay owes its origin. 2d, 

 That an examination of the deposits, containing, in numerous localities, sea-shells 

 generally mutilated, suggests a submarine origin. 3d, That the way in which 

 the deposit has been driven forwards, and pushed between older rocks, indicates 

 pressure by some agent of enormous weight and magnitude. 4dh, That icebergs 

 and shore-ice would probably answer these conditions, and are seen now in the 

 Arctic regions producing similar effects. 



Assuming that the facts adduced at all events establish the probability of 

 the theory, that icebergs and shore-ice would account for most of the drift 

 phenomena in Great Britain, I proceed to offer a few remarks as to the circum- 

 stances and condition of Great Britain at that time. 



Most geologists are agreed that, at the period of the boulder-clay, the sea 

 must have stood greatly higher upon the land than at present. Beds of sea- 



* Lond. Geolog. Journal for 1868, vol. xvi. p. 433. 

 f Franklin's Journey in 1823, pp. 499, 501, 583. 

 + Phil. Journal for 1841, vol. xix. p. 530. 



VOL. XXV. PART II, 8 



