Notes on Geology and Mineralogy of Afghanistan. 591 



trating the readily yielding sides than the bottom, converted 

 into a sort of pavement by the stones rolled down from the 

 mountains. The stream has not however of late years occu- 

 pied the whole breadth, though in former times, before it 

 had cut itself so deep a bed, it would appear to have done 

 so near Girishk : for example, there are ruins at opposite 

 sides of the river, of forts known to have been contempora- 

 neous, and under which the water must have flowed (for 

 they are built in a semicircle, without a wall on the river 

 face,) though there is a space of four miles between them. 

 The stream now hugs the left bank, above which rises in 

 vast mounds the sandy desert. The ancient right bank is 

 well marked by the high cliffs of the plain before mention- 

 ed, which are every where hollowed and indurated by the 

 action of water. The rich space between this band and the 

 modern channel, of which the average breadth is rather 

 more than two miles, is the country of Gurmsehl."* 



The " sort of pavement of stones" here alluded to as 

 forming the bottom of the river's bed, is the conglomerate, 

 and the " yielding sides" are the sands and alluvial soils 

 which, as we travel south, are seen to overlie the conglome- 

 rate. The cliffs forming " the ancient right bank" are com- 

 posed of the same indurated conglomerate, but that in- 

 duration is in no way caused by the action of the river, as 

 Captain Conolly's remarks would lead one to suppose, but 

 is due to causes which must have been in operation before 

 the river Helmund commenced its existence. The plains 

 extending for many miles on either side of the river at 

 Greeshk are composed of the same rock, and it is therefore 

 evident that in such situations its waters could have exer- 

 cised no influence whatever. The river certainly has not 

 filled its bed for many years, and the high conglomerate 

 banks, between which and the modern stream a broad belt 

 of rich cultivation intervenes, and which forms in truth the 



* Vide Journal As. Soc. Bengal, No. 103, page 712. 



