394 SEDIMENTARY ROCKS IN MOUNTAIN VALLEYS. 



fact to which we have already drawn attention, of 

 areas of the sedimentary rocks being bodily carried 

 up into the valleys, between the principal ridges, and 

 left lying there in the same order in which they exist 

 beneath the plain; and we agree with Mr. Ball in 

 regarding this as strong evidence of the simultaneous 

 upheaval of both ridges furthermore these sedimen- 

 tary rocks being of the tertiary period in most cases, 

 it follows that their elevation is of more recent date 

 than they are. Thus in the opinion of the superinten- 

 dent of the geological survey of India, and other 

 officers of that department, the Himalayas are " generally 

 supposed to have been upraised in late tertiary times." * 

 The Encyclopedia Britannica takes the same view, f 

 In closing this brief survey of the probable origin 

 of mountains, a few words as to their vast antiquity 

 from the point of view of historical \\n\e may be desirable. 

 Modern though they certainly are, when compared 

 with the mighty epochs represented by geological time, 

 we venture to assert that their watercourses supply 

 ample evidence to establish the great antiquity of existing 

 mountain ranges: for a ridge once formed upon the 

 earth's surface will remain the watershed of the surround- 

 ing country for untold ages; and no observant man 

 can have examined the gorges issuing from a great 

 mountain range, cut as they frequently are for hundreds 

 of feet perpendicularly through the living rock, without 

 being impressed with the vast periods of time which 

 the water must have taken to wear away such conduits. 



* Manual of the Geology of India, compiled from the Observations of 

 the Indian Surveys, by order of the Government of India, by H. B. 

 Medlicott, superintendent, and W. T. Blandford, F.R.S., published 

 Calcutta 1875, Part n, chap, xxii, p. 520. 



j- See Encyclopaedia Britannica, gth Edition, Vol. xi., p. 828. 



