290 On the Gypsum of the Himalaya. [July, 



Saussure, Daubuisson, and others, have conceived some of the Alpine 

 gypsum to be primary ; that of Cogne, mentioned by Brochant, as dis- 

 covered and considered primitive by Daubuisson, obtaining the dis- 

 tinction from a superincumbent stratum of lime-stone " a little crys- 

 talline, blueish grey, and very schistose from a mixture of talc ;" 

 the gypsum having no outcrop whatever, and consequently being im- 

 bedded in the above rock ; and, as M. Brochant says there is every 

 reason to suppose that the schistose limestone of the roof contains 

 quartzose veins, as also happens in transition limestone, he, rather 

 gratuitously, concludes that the formation is contemporaneous. 



The presence of these quartzose veins, which is the type of tran- 

 sition, and the absence of outcrop, rest on the mere ipse dixit 

 of the villagers, and can hardly be received as proofs in a matter 

 where direct geological accuracy is concerned. The deposit also of 

 "Val Canaria is a very doubtful proof of the existence of gypsum pri- 

 marily. The fact of its underlying mica slate is contradicted by 

 Brochant, who thinks the same of his transition variety. The proof 

 of its being primitive is therefore still far from being ascertained, and 

 I propose in a future part of this paper to suggest causes that might 

 place in doubt, even the superincumbence of mica slate as a proof 

 of its antiquity. The general description given by writers on the 

 subject of Alpine gypsum, so closely applies itself to the mineral 

 lately found in the line of mountains north of the Dehra Dun, both 

 in regard to its position and its attendant rocks, that a comparison 

 becomes exceedingly interesting, as illustrative of the difference, if 

 there be any, of the gypsum decidedly secondary, and that which is 

 accompanied by rocks of evidently a more ancient formation. 



The localities which have come under my immediate observation are 

 two of those adverted to by Captain Herbert, in his communication 

 to the Society. The first near Sansardhdra, immediately on the skirts 

 of the mountains bounding the valley of Dehra, on the north : the 

 second about four miles further north, near the village of Salkofh^ 

 differing in position most essentially from the former, though resem- 

 bling it in character ; to enter into a detail of each, with its respective 

 peculiarities will be necessary in furtherance of the history of the 

 rock in question. 



Gypsum opposite Sansardhara. 



Immediately opposite the stalactitic caves, and beyond the rapid 



stream that runs towards the village of Nagul, a passage into the 



mountains is effected up the course of one of its tributaries, which 



branching off to the left, leads you at once to the gypsum, the prox- 



