Scienlific Intelligence. — Geology. 403 



tliu'd takes a general view of the geological structure ; the fourth 

 exhibits the conclusions drawn by Captain Herbert, from his ob- 

 servations, as compared with theory and inquiries in other, 

 countries ; and the fifth enumerates the mineral productions df 

 the mountains, as far as yet ascertained. In the first division of 

 his subject, Captain Herbert adverts to the supposed elevation 

 of the great central table of Asia, whence arise so many consi- 

 derable streams, and which, although surrounded by lofty baiv 

 riers, is not necessarily of the great height which has been ima- 

 gined. His observations, however, are restricted to a part only 

 of the barrier, which is not among its least important portions. 

 He estimates the superficial extent of the mountainous region, 

 now comprised within the boundary of British India, at about 

 23,000 square miles. The whole of this is mountainous, but 

 the mountains do not offer, to an ordinary observer, the idea of 

 regular chains ; and it is only with refei'ence to the course of the 

 rivers that their principal branches can be discriminated from 

 each other. They are then distinguishable into different ranges, 

 of which the Indo-Gangetic chain is the most extensive. With 

 respect to elevation, Captain Herbert observes, that, whilst in 

 South America, there is but one peak, Chimborazo, which ex- 

 ceeds 20,000 feet, and not more than five which are about 

 18,000 ; there are no fewer than twenty-eight peaks in the 

 Himalaya, which overtop Chimbarazo, one of which is about 

 25,000 feet, forty-four which exceed the three next of the 

 American elevations, and more than a hundred which tower 

 above the next in height : facts which he justly considers as 

 more satisfactory proofs of the superior elevation of these 

 mountains than the greater loftiness of an isolated summit. 

 Through this range the only rock sufficiently extensive to be 

 characteristic of its formation is gneiss, the other rocks occurring 

 only in veins or beds. It occurs in three principal states, or 

 laminated, granular, and what Captain Herbert terms glandu- 

 lar. Granite veins are numerous in some positions, but this 

 mineral does not form a leading feature of these mountains, in 

 which they offer a remarkable difference from the structure of 

 the Andes. Various other differences, equally remarkable, oc- 

 cur, one of which is the total absence of volcanoes in the Hi« 



