66 THE HISTORY OF THE NORTH ATLANTIC 



present dissociation of the axis of rotation from the magnetic 

 poles, and with changes of cUmate, have attracted some atten- 

 tion,^ and probably deserve further consideration on the part 

 of physicists. In so far as geological evidence is concerned, 

 it would seem that the general association of crumpling with 

 metamorphism indicates a certain rapidity in the process of 

 mountain-making, and consequent development of heat ; and 

 the arrangement of the older rocks around the Arctic basin for- 

 bids us from assuming any extensive movement of the axis of 

 rotation, though it does not exclude changes to a Hmited extent. 



(8) It appears from the above that mountains and conti- 

 nental elevations may be of three kinds, {a) They may con- 

 sist of material thrown out of volcanic rents, like earth out of 

 a mole burrow. Mountains like Vesuvius and ^tna are of 

 this kind, {b) They may be parts of wide ridges or chains 

 variously cut and modified by rains and rivers. The Lebanon 

 and the Catskill Mountains are cases in point, {c) They may 

 be lines of crumpling by lateral pressure. The greatest moun- 

 tains, like the Cordillera, the Alps, and the Appalachians are of 

 this kind, and such mountains may represent lateral pressure 

 occurring at various times, and whose results have been greatly 

 modified subsequently. 



I wish to formulate these principles as distinctly as possible, 

 and as the result of all the long series of observations^ calcu- 

 lations, and discussions since the time of Werner and Hutton, 

 and in which a vast number of able physicists and naturalists 

 have borne a part, because they may be considered as certain 

 deductions from our actual knowledge, and because they lie 

 at the foundation of a rational physical geology. 



We may roughly popularise these deductions by comparing 

 the earth to a drupe or stone-fruit, such as a plum or peach 



^ See recent papers of Oldham and Fisher, in Geological Magazine, and 

 Philosophical Magazine, July, 1886. Also Peroche, " Revol. Polaires." 

 Paris, 1886. 



