OHIO IX AND AGE OF THE SUITS HEAT. 295 



two miles would not deflect the Pole much over half a 

 degree. Assuming the mean elevation of the continents 

 of Europe and Asia to be 1000 feet, Professor Houghton 

 calculates that their removal would displace the Pole 

 only 199"4 miles. 



It may now be admitted as settled that if the earth 

 be perfectly rigid, the climate of our globe could never 

 possibly have been affected by any change in the 

 axis of rotation. But it is maintained that, if the 

 earth can yield as a whole so as to adapt its form to a 

 new axis of rotation, the effects may be cumulative, 

 and that a displacement of the Pole as much as 10° or 

 15° is possible. 



But then if the earth be able to adapt its form to a 

 change in the axis of rotation, there is no reason why 

 it may not be able to adapt its form to a cha age in the 

 rale of rotation, and, if so, the flattening at the Poles 

 and the bulging at the Equator would diminish as 

 the rate of rotation diminished, even supposing there 

 were no denudation going on. 



Argument from the Secular Cooling of the Earth. — 

 The earth, like the sun, is a body in the process of 

 cooling, and it is evident that if we go back sufficiently 

 far we shall reach a period when it was in a molten 

 condition. Calculating by means of Fourier's mathe- 

 matical theory of the conductivity of heat, Sir William 

 Thomson has endeavoured to determine how many 

 years must have elapsed since solidification of the 

 earth's crust may have taken place. This argument 

 is undoubtedly the most reliable of the three. Never- 

 theless, the data on the subject are yet very imperfect, 

 so that no very definite result can be arrived at by 

 this means as to the actual age of the earth. In fact, 

 this is obvious from the very wide limits assigned by 

 him within which solidification probably took place. 



