142 DISCUSSIONS IN CLIMATOLOGY. 



have to be melted off the ground before the warmth of 

 the interglacial period would commence. So long as a 

 single inch of ice covered the surface of the country, 

 the cold would continue. Ice, as we have seen, by 

 chilling the air, induces fresh snow to fall; and, of 

 course, it is only when the amount of ice annually 

 melted exceeds that being formed from the falling 

 snow, that a diminution in the thickness of the sheet 

 would begin to take place. A real melting of the ice, 

 and consequent decrease in the thickness of the sheet, 

 would probably not commence till the astronomical 

 and physical agencies in operation during the glacial 

 period began to act in an opposite direction. In short, 

 it would be the favourable conditions of the inter- 

 glacial period that would effectually remove the ice ; 

 and it would be then, and only then, that the warmth 

 would begin ; while, again, at the close of the period, 

 when the first inch of ice made its appearance on the 

 surface of the country, the interglacial condition of 

 climate would come to an end. The time required to 

 remove the ice does not prevent an interglacial con- 

 dition of climate ; it only somewhat shortens its 

 duration. 



There is another circumstance worthy of notice here. 

 It is this : as the mild and equable character of the 

 climate during interglacial periods resulted to a large 

 extent from the enormous transference of equatorial 

 heat, and its distribution over temperate and polar 

 regions, the difference of climatic conditions between 

 the subtropical and the temperate and polar regions 

 would be less marked than at present; in other words, 

 the temperature would not differ so much with latitude 

 as it does at present. This, as we have seen, is a con- 

 clusion which is fully borne out by geological and 

 palseontological facts. 



