Nov. 1850. GEOLOGICAL SPECULATIONS. 325 



floored valleys of the southern watershed may be attributed 

 to the scouring action of higher tides on a boisterous rocky 

 coast. These views are confirmed by an examination of 

 the east shores of the Bay of Bengal, and particularly by a 

 comparison of the features of the country about Silhet, now 

 nearly 200 miles distant from the sea, with those of the 

 Chittagong coast, with which they are identical. 



The geological features of the Khasia are in many 

 respects so similar to those of the Vindhya, Kymore, Behar, 

 and Rajmahal mountains, that they have been considered 

 by some observers as an eastern prolongation of that great 

 chain, from which they are geographically separated by the 

 delta of the Ganges and Burrampooter. The general contour 

 of the mountains, and of their sandstone cliffs, is the same, 

 and the association of this rock with coal and lime is a 

 marked point of similarity ; there is, however, this differ- 

 ence between them, that the coal-shales of Khasia and 

 limestone of Behar are non-fossiliferous, while the lime of 

 Khasia and the coal-shales of Behar contain fossils. 



The prevalent north-east strike of the gneiss is the same 

 in both, differing from the Himalaya, where the stratified 

 rocks generally strike north-west. The nummulites of the 

 limestone are the only known means we have of forming 

 an approximate estimate of the age of the Khasia coal, 

 which is the most interesting feature in the geology of the 

 range : these fossils have been examined by MM. Archiac 

 and Jules Haines,* who have pronounced the species 

 collected by Dr. Thomson and myself to be the same as 

 those found in the nummulite rocks of north-west India, 

 Scinde, and Arabia. 



* " Description des Auimaux Fossilea des Indes Orientales," p. 178. These 

 species are Nummulites scabra, Lamarck, N. obtusa, Sowerby, N. Lucusana, 

 Deshnyes, and N. Beaumonti, d'Arch. and Haines. 



