380 Glacial Epoch in Britain. 



from the sun than when eccentricity is at a minimum, or 

 about 8 \ millions further than its greatest distance now. 

 The earth, therefore, in aphelion would be more than 

 1 4 millions of miles farther from the sun than when in 

 perihelion, and if, in accordance with the precession of 

 the equinoxes, it so happened that winter in the 

 northern hemisphere took place when the earth is 

 furthest from the sun, then by calculation it has been 

 shown that ; the direct heat of the sun in winter would 

 be one-fifth less during that season than at present, 

 and in summer one-fifth greater.' But this extra 

 amount of heat in summer would even less have 

 sufficed to remove the snow and ice then, than it suffices 

 to remove it from Victoria Land at the present day ; 

 for just as that region is all summer apt to be involved 

 in clouds and fogs by vapours, due to partial evaporation 

 of melting snow, even so on a greater scale the same 

 effect must have been produced in old epochs, when 

 greater glacial epochs took place alternately in the 

 northern and southern hemispheres. 



It was during part, or in parts of one of these periods, 

 that great part of what is now the British Islands, was 

 last almost entirely covered with ice, for, as I have 

 already shown, similar phenomena are periodical, and 

 have occurred in several old geological epochs. I do 

 not say that our area consisted of islands during the 

 whole of the last Glacial epoch, and probably during 

 part of it they were united with the Continent, and the 

 average level of the land may then have been somewhat 

 higher than at present, by elevation of the whole, and 

 also because since the first appearance of British glaciers 

 it has suffered much degradation ; but whether this was 

 so or not, the mountains and much of the lowlands were 

 long covered with a universal coating of ice, pro- 



