MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 681 



Assuming, then, that icebergs and shore-ice prevailed in the sea which covered 

 the British Islands and other parts of Northern Europe, how would these operate 

 as agents in the production of boulder-clay ? In some places, boulder-clay lies 

 over stratified beds ; in other places, boulder-clay is covered by them. In the 

 former case, it may be supposed that an iceberg pierced through the sea-bottom 

 only to a certain depth, leaving the part next to the rocks untouched. In the 

 latter case, it may be supposed that more sediment was subsequently deposited 

 by currents over the disturbed beds, and remained undisturbed. There are 

 cases where, in one section, there have been found as many as three layers of 

 boulder-clay, each from 20 to 30 feet thick, alternating with laminated beds of 

 clay and sand. In such cases it is only necessary to suppose that icebergs came, 

 drifted by currents, at different periods, some being larger and deeper in the water 

 than others. 



If the glacier theory be adopted, which assumes that the boulder-clay was 

 formed on the land at the end of a glacier, or under its mass, then to account 

 for these alternations of marine beds with boulder-clay, there must have been as 

 many oscillations of the land below and above the sea as there are layers of 

 boulder-clay — a supposition surely very improbable. 



9. But a difficulty here suggests itself. Where did these icebergs come 

 from ? They could not have been generated by Scotch or English glaciers, if, 

 when the land was submerged, there were no mountains higher than 1500 

 feet. 



Where, then, was the high land to give birth to glaciers from which these ice- 

 bergs came ; and was there a current in the ocean so strong and extensive as to 

 bring these icebergs over North- Western Europe, and in the direction indicated 

 by the transported boulders and rock surface striations ? 



That the physical geography of the Northern Hemisphere must have been 

 totally different from what it now is, is plain from the circumstance that the 

 climate was so different. Perhaps the colder climate was brought about by the 

 same conditions, which would suit the formation of icebergs, and the existence of 

 a great current from the north-west by which they were drifted. The problem 

 is to ascertain what circumstances would produce an Arctic temperature in North- 

 western Europe, and so far south as latitude 51°. 



Labrador is in the latitude of Great Britain. What are the circumstances 

 which give to that country a mean annual temperature of 25°, and a mid- winter 

 temperature of — 50°? Two causes co-operate — an Arctic current, loaded with ice- 

 bergs, which flows past its shores ; arid proximity to the high land of Greenland, 

 whose snow and ice chill the atmosphere. 



From this fact, is it not probable that North- Western Europe, when it pos- 

 sessed a Labrador climate, was indebted for it to similar conditions ? 



One thing is certain— the Gulf Stream could not then have flowed along its 



