701 



II. Postscript to a Paper " On the Deflection of the Plumb-line 

 in India, caused by the Attraction of the Himalayan 

 Mountains." By the Venerable Archdeacon PRATT. Com- 

 municated by Professor STOKES, Sec. R.S. Received 

 February 21, 1859. 



(Abstract.) 



Since transmitting his Paper " On the deflection of the Plumb-line 

 in India caused by the attraction of the Himalaya Mountains*," the 

 author has had the advantage of seeing the pages of Major R. 

 Strachey's work on the physical geography of the Himalayas, now 

 passing through the press ; and being permitted to make use of them, 

 he availed himself of the important information therein contained to 

 add a postscript to his former communication. 



Major Strachey thinks that none of the numerous ranges commonly 

 marked on maps of Thibet, have any special definite existence as 

 mountain chains, apart from the general mass of the table-land ; and 

 that this country should not be considered to be as if in the interval 

 between the two so-called chains of the Himalaya and Kouenlun, 

 but that it is in reality the summit of a great protuberance, above 

 the general level of the earth's surface, of which the supposed 

 Kouenlun and Himalaya are nothing more than the north and south 

 faces, while the other ranges are but corrugations of the table-land 

 more or less marked. The plains of India which skirt the foot of 

 the table-land, to an extent of 1500 miles, nowhere have an elevation 

 exceeding 1 200 feet above the sea, the average being much less ; and 

 there is reason to think that the northern plateau of Yarkend and 

 Khotan, like the country about Bukhara, lies at a very small eleva- 

 tion, probably not more than 1000 or 2000 feet above the sea, 

 while on the borders of the Caspian the surface descends below the 

 sea-level. 



On comparing the information contained in Major Strachey* s work 

 with the assumptions as to height above the sea-level, adopted by 

 the author in his former paper from the best data then in his pos- 

 session, it appears that the mean height of the table-land was con- 

 siderably under-estimated ; while on the other hand attracting masses 

 were supposed to lie still further north which really have no existence. 



* Proc. Roy. Soc. vol. ix. p. 493. 



