igoS] THE PHYSICS OF THE EARTH. 227 



But, however vast the Andes may seem to us, it should be remembered that 

 they form but an insignificant portion of the globe itself. Aconcagua is 

 about 1/2,000 of the earth's diameter, which is relatively not more than a 

 pimple 1/30 of an inch high on the skin of a tall man." (Ency. Brit., Vol. 

 II, pp. 15-16.) 



The account here given of how the Andes were formed seems 

 exceedingly instructive. In the sea troughs formerly existing be- 

 tween the ocean and the eastern range, which was the first thrown 

 up, we have a complete explanation of the extraordinary depth of 

 sedimentation ; for in such trenches adjacent to a new range the 

 rate of sedimentation would be a maximum. The subsequent up- 

 lifting of the western side of the sea troughs, with the vast lateral 

 folding and compression necessarily accompanying this movement, 

 accounts for the plateaus, valleys and general structure of the 

 Andes, as well as for the violent volcanic outbreaks, which are said 

 to greatly predominate in the range nearest the sea, from which 

 the expulsion of lava giving rise to this mighty Cordillera pro- 

 ceeded. The vastness and height of the Andes and the terrific 

 forces operating to erect this gigantic wall along the shore of the 

 continent is a true measure of the secular leakage of the Pacific 

 Ocean, and of the automatic relief it finds by folding the earth's 

 crust along the border, in the countless successive expulsions of 

 lava from beneath the bed of the sea. It is needless to point 

 out how perfectly the new theory explains the persistence of the 

 earthquake belt along the western shore of South America, and 

 of the seismic sea waves by which that region is so often afflicted. 

 It is obvious that the forces which uplifted the mountain also car- 

 ried up the plateaus enclosed between the various ranges. 



§ 35. The Himalayas. — The following luminous account of the 

 Himalayas by the late Lieutenant General Sir Richard Strachey, 

 Encyclopedia Brifaiinica. article " Himalayas," is of extreme in- 

 terest. General Strache}' resided in India for many years, and made 

 a life long study of the Geology and Geography of Central Asia. 

 He was the principal authority of his time on this little explored 

 continent and died February 12, 1908, at the age of 91 years. 



" Scientific investigation has clearly shown that, so far as the main 

 characteristics of the mountains are concerned, the natural boundaries of 

 the Himalayan system must be carried much farther than had at first been 



