28 Economic Geology. 



sent site of Calcutta ; and taking his data from the results of 

 personal observation on the transporting power of rapid cur- 

 rents, he estimates the distance of these mountains as not 

 greater than 20 or 30 miles.* — Resting on this bed of coarse 

 conglomerate, the entire depth of which is unknown, al- 

 though it cannot be less than 80 feet, the bore having 

 pierced it to that extent, there are beds of carbonaceous 

 matter and lacrustine clay bearing the clearest evidence of 

 having been quietly deposited on a marshy surface richly 

 clothed with vegetation. Ere this could have taken place, 

 the powerful currents indicated by the gravel must have 

 been arrested, and as this could only be effected by a great 

 lowering of the inclination of the bed of the river, we may 

 infer the check arose from the entire subsidence of the 

 range of hills above alluded to. The extent to which this 

 took place it is impossible for us to estimate, but the depo- 

 sits which the river continued to make would repose upon 

 the depressed masses, and were boring operations to be 

 carried on successfully in such localities, they would ulti- 

 mately expose these again to our observation. Supposing 

 then, as without impropriety we may do, that the rocks of 

 which these hills were composed stretched away beneath 

 the conglomerate bed formed by the large gravel borne 

 along by the torrent issuing from them, we are led to believe 

 that had the Fort William boring operations been success- 

 fully carried through the entire depth of the conglomerate, 

 the auger would then have impinged on the solid rock; and 

 if so, the question naturally occurs — Would the experiment 

 have terminated favourably ? When we remember that the 

 conglomerate was almost entirely composed of debris from 



* The reader who may wish to see this subject treated in greater 

 detail, is referred to a paper " On the Structure of the Delta of the 

 Ganges," by the writer, in the 3rd vol. of the Calcutta Journal of 

 Natural History, and more especially to Dr. M'Celland's editorial re- 

 mark on that paper in the same work. 



