Notes on Geology and Mineralogy of Affghanistan. 585 



tracts to which water can be artificially brought, or through 

 which it naturally flows, being productive, and well culti- 

 vated ; while all beyond the reach of irrigation, (and this is 

 always by far the greater portion of the valleys) remains an 

 arid waste. 



Selenite, or sulphate of lime, is dug out of the plain on 

 the Ghuznee side of Candahar, and when burnt to lime 

 forms the finest plaster used in the buildings of the city. It 

 is said, that the discovery of this mineral was made in the 

 time of Ahmed Shah, who considered it so valuable an 

 acquisition, that he caused public prayers and thanksgivings 

 to be offered up, and celebrated the event with feasting and 

 charitable gifts. The mineral is known to the Affghans by 

 the name of " Gutch" and occurs about three feet below 

 the surface of the alluvial soil ; it contains many pebbles of 

 trap rocks and limestone imbedded in it, which would tend 

 to prove it to have been an aqueous deposit, unless indeed, 

 which is perhaps more probable, it has arisen from the 

 infiltration through the soil, of water holding sulphuric acid 

 derived from the decomposition of pyrites and the volcanic 

 rocks of the district, which acid combining again with the 

 calcareous particles derived from the limestone ranges and 

 disseminated through the soils, may have formed a bed of 

 loosely aggregated crystals of sulphate of lime. 



The range of hills dividing the valley of the Argandab 

 from Candahar, is composed of limestone intimately associ- 

 ated with volcanic rocks, a range of which runs parallel 

 along the base of the mountains, consisting of greenstone, 

 basalt, serpentine and clay-stones ; while the shelving plains 

 around are covered with fragments of granite, syenite, green- 

 stone, basalt, and various porphyries : some of these have 

 been brought from a distance, especially the granite and 

 some limestones, for I found specimens of both of the latter 

 rocks which I only know positively to occur in situ in the 

 Shah-muksood range beyond the Argandab. Water appears 



