334 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



nearest the valley of the Ganges ; and the process of mountain- 

 formation seems to be such that when several successive ranges are 

 formed and completed that nearest the sea is the highest, probably 

 because the forces there became most nearly vertical. 



In Vol. II, p. 552, Professor Suess says : '' As a result of tangen- 

 tial thrusts the sediment of this (Mediterranean) Sea was folded to- 

 gether and driven upwards as a great mountain range, and the Alps 

 have, therefore, been described as a compressed sea." 



From these considerations, it is obvious that the Alps were 

 injected from several sides, but especially from the side of the 

 valley of the Po. In this way, the successive ranges of the Alps 

 were formed, probably beginning near the north, and working 

 southward ; and thus we see that the valleys of Switzerland are the 

 results of this successive wrinkling of the crust. Many lakes were 

 formed in the Alps, and these contributed their part to the final 

 shaping of the contours of the country. As the country was sur- 

 rounded by seas and traversed by many valleys and lakes, all of 

 which gave the water access to the bowels of the earth where breaks 

 of the rocks were once started, the movements finally became very 

 complex, and hence the great difficulty of unravelirlg the tangled 

 skein of Alpine development. In no other way than this could such 

 a system of mountains have arisen. The average height of the 

 Alpine region is about 4,000 feet, but instead of a level tableland, 

 it is a mass of broken chains and valleys, showing great horizontal 

 crumpling, and also conspicuous and uneven vertical uplifts. The 

 Alps, therefore, afford one of the best illustrations of the theory. 

 For details of the various valleys of the Alps, and the great faults 

 which mark these sunken areas, one may consult Suess, Vol. I, p. 

 200, et seq. 



§24. On the origin of the Himalayas and of the Plateau of Tibet. 



If we study the general character of the Himalayas by means 

 of the excellent vnBjp given in the article, " India," Encyclopedia 

 Britannica, ninth edition, we shall find that the most conspicuous 

 feature of this great chain is the prominence of the jutting spurs on 

 the south, facing the ocean. Perhaps a few remarks ought to be 

 made about the process by which these spurs originate. 



We have seen that it was by the injection of lava from the sea 



