Geological Society. 383 



which asserts the synchronous elevation of distant mountain chains, 

 parallel to each other. 



As the latter part of this subject will, I doubt not, still undergo 

 ample discussion, both on the continent and in England, we must 

 wait for the development of numerous facts before we can be 

 warranted in arriving at general conclusions ; and I need scarcely 

 urge all our working brethren, to try the adequacy of M. de Beaumont's 

 ingenious theory by an appeal to nature in our own country. 



The new work of M. de Humboldt (" Fragmens Asiatiques") pre- 

 sents us with some striking phaenomena. 



This illustrious traveller, not content with having been the first to 

 clear away the mists which obscured our knowledge of the physi- 

 cal structure of the great continent of South America, has, with all 

 the energy of his character, embarked in the attempt to throw light 

 upon the unexplored regions of the continent of Asia; and we 

 have now before us the outline of his own observations and inquiries, 

 together with those of MM. Rose and Ehrenberg, made during a 

 journey to the Tartarian frontiers of China, under the auspices of the 

 Government of Russia. 



Of the four great mountain chains which traverse Asia from west 

 to east, one of them, the Thian Chan, is said to be marked by a 

 line of active volcanos, the chief of which is situated at a distance 

 of from three hundred to four hundred leagues from any sea. This 

 phaenomenon is in strict accordance with the recent observations of 

 M. Riippel, in the interior of Africa, and M. de Humboldt infers 

 from it, that the received doctrine of the sea being necessarily a 

 proximate agent in the causation of volcanic outbursts, is errone- 

 ous ; and he conceives that the greater frequency of active volcanos 

 along maritime tracts, depends on the less thickness and conse- 

 quently greater weakness of the earth's cr\ist upon such lines of 

 coast, than in those parts where massive continents have been 

 raised ; and that when they occur in the centre of continents, as in 

 central Asia, the molten and gaseous matters find vent through 

 deep rents and fissures. — I need scarcely remind you that the same 

 view had previously been entertained by Mr. Poulett Scrope. 



M. de Humboldt believes that the four great chains of Asiatic 

 mountains are parallel to each other; and that this circumstance 

 tends powerfully to confirm the theory of M. Elie de Beaumont. 

 As, however, the personal observations of the author have not ex- 

 tended beyond the Altai, we are as yet wholly unprovided with 

 evidence, whereon the synchronism of the elevations of these moun- 

 tains, so distant from each other, can be established ; for should their 

 parallelism be confirmed by subsequent observations, geologists are 

 still compelled to pause in drawing conclusions as to their contem- 

 poraneity of elevation, until the precise nature of the sedimentary 

 deposits on the flanks of each chain, and the manner in which these 

 sediments have been affected, shall have been clearly ascertained. 



The existence of a vast depression on the earth's surface, extend- 

 ing beyond the Caspian and the Oural, whicli had been partially 

 noticed by P^nglehardt and old travellers, and recently, as re- 

 spects 



