and its Influence on Climate. 441 



One thing, however, is certain, that this continent, whatever 

 its extent may be, is covered with a vast sheet of ice. This sheet 

 is known to be upwards of 1000 feet thick at its edges. And there 

 are reasons of a mechanical nature (which will come under our 

 notice perhaps on a future occasion) which prove that the thick- 

 ness of the sheet in the centre of this continent must be 

 enormous. 



Assuming, then, that the southern ice-cap extends on an ave- 

 rage down to lat. 70°, it will therefore be equal to ^^ of the 

 entire surface of the globe. The proportion of land to that of 

 water, taking into account the antarctic continent, according to 

 Mr. Saunders*, is as 526 to 1272. The southern ice-cap will 

 therefore be equal to ^^ of the area covered by water. The 

 density of ice to that of water being taken at # 92 to 1, it follows 

 that 25 feet 6 inches of ice melted from off the face of the 

 antarctic continent would raise the level of the ocean 1 foot. 

 If 470 feet were melted off — and this is by no means an extra- 

 vagant supposition, when we reflect, that for every 18 pounds 

 of ice presently melted an additional pound or two pounds, 

 or perhaps more, would then be melted, and that for many 

 ages in succession — the water thus produced from the melted 

 ice would raise the level of the sea 18 feet 5 inches. The 

 removal of the 470 feet of solid ice (which must be but a very 

 small fraction of the total quantity of ice lying upon the ant- 

 arctic continent) would shift the earth's centre of gravity about 

 7 feet to the north of its present position. The shifting of the 

 centre of gravity would cause the sea to sink on the southern 

 hemisphere and rise on the northernf. And the quantity of 

 water thus transferred from the southern hemisphere to the north- 

 ern would carry the centre of gravity about 1 foot further, and 

 thus give a total displacement of the centre to the extent of 

 about 8 feet. The sea would therefore rise about 8 feet at the 

 North Pole, and in the latitude of Glasgow about 6 feet 7 inches. 

 This, added to the rise of 18 feet 5 inches, occasioned by the 

 melting of the ice, would give 25 feet as the total rise in the 

 latitude of Scotland 11,700 years ago. 



Each square foot of surface at the poles 11,700 years ago 

 would be receiving 18,223,100 foot-pounds more of heat an- 

 nually than at present. If we deduct 22 per cent, as the 

 amount absorbed in passing through the atmosphere, we have 

 14,214,000 foot-pounds. This would be sufficient to melt 2*26 

 feet of ice. But if 50 per cent, were cut off instead of 22 per 

 cent, 1*45 cubic foot would be melted. In this case the 470 



* Lyell's ' Principles,' vol. i. p. 257. 

 t Phil. Mag. for April 1866. 



