6 DISCUSSIONS IN CLIMATOLOGY. 



never shifted its position to any great extent. "If 

 we examine," he says, " the localities of the fossil 

 remains of the Arctic regions, and consider carefully 

 their relations to the position of the present North 

 Pole, we find that we can demonstrate that the Pole 

 has not sensibly changed its place during geological 

 periods, and that the hypothesis of a shifting pole 

 (even if permitted by mechanical considerations) is 

 inadmissible to account for changes in geological 

 climates." 



There is no geological evidence to show that, at 

 least since Silurian times, the Atlantic and Pacific 

 were ever in their broad features otherwise than 

 they are now — two immense oceans separated by the 

 Eastern and Western continents — and there is not the 

 shadow of a reason to conclude that the poles have 

 ever shifted much from their present position. On 

 this point I cannot do better than quote the opinion 

 expressed by Sir William Thomson : — 



"As to changes of the earth's axis, I need not repeat the 

 statement of dynamical principles which I gave with experi- 

 mental illustrations to the Society three years ago ; but may 

 remind you of the chief result, which is that, for steady rota- 

 tion, the axis round which the earth revolves must be a 

 'principal axis of inertia,' — that is to say, such an axis that 

 the centrifugal forces called into play by the rotation balance 

 one another. The vast transpositions of matter at the earth's 

 surface, or else distortions of the whole solid mass, which 

 must have taken place to alter the axis sufficiently to pro- 

 duce sensible changes of the climate in any region, must be 

 considered and shown to be possible or probable before any 

 hypothesis accounting for changes of climate by alterations 

 of the axis can be admitted. This question has been exhaus- 

 tively dealt with by Professor George Darwin, in a paper 

 recently communicated to the Royal Society of London, and 



