MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 687 



is also related that Sir James Ross once saw an iceberg capsize, bringing up mud 

 and stones to a height of more than 100 feet from the sea-bottom. Perhaps, 

 therefore, the anomalous position of some boulders, in respect of being above the 

 level of the parent rock, may, on the iceberg theory, admit of some explanation. 

 On the glacier theory they admit of none. 



(6.) The chief objection to the views which they have submitted in this 

 Memoir, may be found in the following paragraph : — 



" The iceberg hypothesis will not account for the phenomena. We cannot 

 conceive of a set of ice-rafts moving for ages in one persistent direction within a 

 given area of the sea. A group of huge bergs in high latitudes often exhibits, on 

 the contrary, a scene of the wildest confusion. If we could examine some parts of 

 the sea-bottom off the Greenland coast, we should find them bruised and scored 

 in every direction by the grounding of the bewildered icefloes."* 



Whilst, in this passage, it is admitted that rocks can be smoothed and striated 

 by icebergs and icefloes, it is said that the "persistent direction " in which the 

 agents must have moved to produce the " phenomena," indicates some other 

 agency than icebergs, because these icebergs would not have moved " for ages in 

 one persistent direction." 



The opinion thus expressed is not supported by evidence, and, moreover, is 

 inconsistent with all the probabilities of the case. It is true we cannot see the 

 markings made on the rocks which form the sea-bottom off Greenland, but, as 

 there is an Arctic current always flowing past that coast out of the Arctic circle, 

 loaded with icebergs and shore ice, the great probability is, that the scorings are 

 not " in every direction," but generally in a direction coincident with that of the 

 current. 



At the epoch of the boulder-clay in Scotland, I have assumed that there was 

 a north-west Arctic current which flowed down on Great Britain, a current of 

 greater strength and extent than any of the existing Arctic currents ; and I have 

 suggested some reasons for the probable existence of such a current. If icebergs 

 were drifted by it over the submerged land, is it not presumable that the scorings 

 on the rocks would be all approximately " in one persistent direction? " 



At all events, is there not more likelihood of this one persistent direction 

 being produced — keeping in view the great extent of the area on the earth's 

 surface over which it prevails — by an oceanic current loaded with ice, than by 

 any imaginable system of glaciers or ice-cakes ? 



11. In a former part of this Memoir I stated, that whilst the evidence from 

 various sources showed that the agency concerned in abrading, striating, and 

 transporting, had moved generally in a south-east direction, there were exceptions, 

 which, however, did not militate against my views as to the origin of boulder- 

 clay. 



* Glacial Drift, by A. Geikie, p. 75. 

 VOL. XXV. PART II. 8 Q 



