MOUNTAIN-MAKING. 105 



been pushed eastward by the Pacific area more than two degrees of lon- 

 gitude, and Claypole affirms that the sediments of the Appalachians 

 have been reduced to one-third of their original breadth by the pressure 

 of the Atlantic basin. 



All this is explicable at once on the old contraction theory, so ably ex- 

 pounded in this country by Le Conte. The thick resisting ocean basins 

 have settled downward toward the center of the earth ; they have at the 

 same time caused the mobile matter beneath them to ooze out in volcanic 

 ejections or to slide laterally under the lighter parts of the continents. 

 They have thus exerted a great lateral pressure on their sides, much as 

 the thick coating of ice on one of our northern lakes casts up ridges on 

 its margin. It is objected to this that the earth is a rigid mass, and that 

 the zone of lateral pressure by contraction is very superficial ; but rigid- 

 ity is a relative term — everything can be made to submit to adequate 

 pressure ; and however physical demonstration may establish the solidity 

 of the earth, we may say as did Galileo, though in a somewhat diff'erent 

 connection, we are sure, nevertheless, that it moves ; and the sediments 

 that make up the mountains are the thinnest possible veneer, the mere 

 coat of varnish on an artificial globe, which can scarcely be laid on so 

 evenly that it will not have inequalities greater than our mountains. 



At the same time I see no reason why we should not avail ourselves of 

 the expansion theory of T. ^Tellard Reade as well. The heated and 

 swelling sediments may have thickened and twisted upward in aid of the 

 lateral })ressure caused by contraction. Nor need Button's theory of 

 isostasy l)e left out, for the whole process of mountain-making seems to 

 imply a certain flotation and pouring sideways of the potential liquidity 

 beneath the crust, which is also evidenced by the volcanic ejections ac- 

 companying or consequent on the elevation, and which add to the 

 l)roduct their injected masses and dikes, overflows of molten rock and 

 ejections of fragmental material. The final result is that mountains can 

 neither be built in a day nor by one cause only. When we have to fold 

 great masses of rock into a third of their original width, to raise them 

 thousands of feet into the air, and to sculpture the rude masses thus pro- 

 vided into grand and beautiful forms, we may well avail ourselves of all 

 ])ossible causes of elevation, as well as of those atmospheric and aqueous 

 denuding agencies which give shape to the whole. 



Uniformitarianism. 



In connection with mountain-making, as well as with other geologic 

 changes, the well worn discussions as to uniformitarianism in geology 

 have been refurbished, more especially in England, where Teall, in his 



