1894-95] J 9 X 



years ago, when Lord Salisbury was Foreign Secretary and 

 there was a panic about the Russian advance in Central Asia, 

 he said people's fears would be much allayed if they would only 

 study large scale maps. We may be allowed to reverse this 

 process, and to suggest that if geologists, instead of only looking 

 at a big map of a small piece of country, were sometimes to look 

 al a map ol the whole British Isles, or, better still, of Europe 

 or the northern hemisphere in its entirety, they would see that 

 in proportion to the whole extent of the globe a very small 

 patch of snow comparitively would be sufficient to form such 

 an icecap as would cover Scotland and stretch over the adjacent 

 sea channels to Ireland, the Isle of Man, and the outer Hebrides. 

 A very slight lowering of the temperature of the northern 

 hemisphere would permit of a sufficient accumulation of snow 

 to accomplish this. Many people are apt to imagine that a 

 glacial epoch requires intense cold for its production. This is 

 due to a misapprehension of the conditions. The centre of 

 Eastern Siberia is said to contain the pole of greatest cold, the 

 thermometer falling in mid-winter to something like eighty 

 degrees below zero of Fahrenheit, or over 100 degrees of frost. 

 Yet Siberia scarcely possesses a glacier, and, notwithstanding 

 that the ground is permanently frozen a few feet below the 

 surface, the winter snow vanishes every summer. As Wallace, 

 in one of his chapters of " Island Life,'' has pointed out, a very 

 moderate fall of temperature below the freezing point, coupled 

 with a large precipitation of moisture, is sufficient to bring about 

 an enormous accumulation of snow. The air currents of Siberia, 

 as of the great plains of North America, are comparatively dry ; 

 consequently, in spite of the cold, there is no accumulation of 

 snow. With mountains to cause precipitation, and the moisture- 

 laden winds round islands, such as Greenland, Iceland, and the 

 North American Archipelago, we have large accumulations of 

 ice. It must be always borne in mind that, whilst heat 

 dissipates itself as soon as formed by being carried away in the 

 form of rain drops or vapour, cold the moment it falls below 

 the freezing point of water becomes locked up, is deposited as 



