THE GLACIAL EPOCH. 49 



thickness could not have been less than a mile ; the thickness of the ice in Scandinavia and 

 other parts of northern Europe miist have been enormous." He therefore assumes that it was 

 . 7000 feet thick at the North Pole, diminishing in thickness towards the Equator, according to 

 a law, into the consideration of which we need not here enter, so that the upper surface of the 

 sheet should curve exactly the same as the land beneath, and ends by bringing out the result 

 that this distribution of ice would have the effect of producing a total submergence of 1000 feet 

 at the North Pole, and a elevation (emergence) of 1000 feet at the South Pole, and of course 

 a lesser accumulation of ice would produce a correspondingly lesser amount of submergence and 

 emergence. 



Now this hypothesis depends upon several assumptions the withdrawal of any of which would 

 be fatal to it. There must have been a vast accumulation of ice in the northern hemisphere, and 

 it must have been thickest towards the Pole ; there must have been not one submergence but 

 several ; and these must have taken place during the continuance of the glacial epoch. 



Now, first as to the ice ; is there any reason for supposing that at the present time it increases 

 in thickness as we approach the Pole ? I have not met with any statement to that effect ; and 

 if the voyagers who have penetrated furthest had observed any indication of its becoming so they 

 would surely have mentioned it. But both from their sketches and descriptions it appears that the 

 ice and glaciers continued of the same thickness as they advanced to the north. Into this question, 

 the dimensions and extent of mountain glaciers, such as those of the AIjds, do not enter. The 

 inferences of Venetz and Cliarj)entier as to the immense extent of these may be perfectly correct ; 

 but it does not follow that their height must have been correspondingl}^ great. They are, however, 

 exceptional and detached, and do not afiect the case of the general mass of polar ice. 



Of course in the case of sea ice it would probably be of a greater depth the further north we 

 go and the greater the cold there is ; but that is nothing to the purpose, for ice is iigliter than 

 ■ water, and an addition to its dei^th would not add to its weight. It is only by accumulation 

 above the level of the sea that additional weight could be produced. As no one has reached the 

 Pole we cannot tell from observation what is the case there, but we may reason from analogy as 

 to what should be found there. If we assume that the cold becomes more intense the nearer we 

 approach the Pole, it by no means follows that there should be more ice there. All the ice of these 

 regions comes from snow. Snow is produced by warm vapour-bearing clouds or atmosphere coming 

 in contact with cold air. It never falls when the thermometer is much below 32° Fahr. The 

 vapour-laden warm aii' which has risen from the tropics and ascended above the colder temperate 

 atmosphere on meeting the frozen air of the Arctic regions, deposits its vapour in the shajje of 

 snow. It is, therefore, always on the boundary of the eternal ice that snow will be deposited. 

 The Pole itself shoiild be clear from fogs, or vapour, or snow. How far the direct heat of the sun 

 might have some efiect in producing them during the short summer wo cannot tell ; but we know 

 that that is not the origin of the snows which fall elsewhere. It comes from the source already 

 mentioned. Increase of snow and ice shoidd therefore be always at the outer margin of the polar 

 ice ; when there is no yearly increase in the cold, when it is standing water between heat and cold, 

 there will be little increase in the breadth or thickness of the ice, for the heat of summer will 

 melt away the increase of winter. But when the cold is on the increase, as when the glacial epoch 

 came on, its last year's gain woidd not be melted away indeed, but stiU there would be no increase 

 of snow or ice in the interior, it would be always at the outer margin that the increase would go 

 on ; and the effect of increased cold would be, not to pile up more ice upon that which already 



