294 On the Gypsum of the Himalaya. [July 



cularly in those deposits where an appearance of stratification or alter- 

 nation with other rocks is apparent) have undergone a change, more 

 sudden, and more general, than what we understand by the term 

 " infiltration," as applies to the formation of calcareous tufa. 

 A question may be put, as to the absence of any impres- 

 sions of vegetable remains, — as to the want of the cylindrical 

 and radiated texture, which so peculiarly marks the tufa in 

 formation ? It must be confessed, that on comparing the minerals, 

 and supposing the process under which they are found to be si- 

 milar ; difficulties, though not irreconcilable to the above supposition, 

 present themselves. In the first place, the action of sulphuric acid 

 would tend in a much more rapid degree to the formation of gypsum, 

 than does the presence of carbonic acid and lime to produce tufa. 

 The same rapid action would create a texture of a totally different 

 quality, and the ingredients themselves would destroy any vegetable 

 remains that might be enveloped in the mass : had the same gradual 

 and slow process that forms the tufa been also exerted in forming 

 gypsum, similar texture would have been the consequence ; and the 

 deposit of the latter would shew at least marks of stalactites, &c. ; 

 but though infiltration is granted as a solution of the problem, the action 

 of time and other causes may have removed those outward and visible 

 marks that might have tended at once to a direct conclusion. Age, 

 pressure, and other causes, are well known as the means of producing 

 most extraordinary changes in the system, and also in the texture 

 and quality of the rocks themselves. The above causes, in a greater 

 or less degree, may have equally exerted their effects on gypsum. 



The obvious transition of the blue limestone into the gypsum at 

 the deposit at Salkofh ; and the extreme purity of the gypsum when 

 in contact with the black fragmentary rock, which scarcely effervesces 

 with acids, leads me to the idea that all these varieties of lime-rock in 

 the proximity of the mineral are simply modifications, caused by the 

 action of the sulphuric acid in a greater or less degree. The springs 

 and rivers in the vicinity of all these formations abound in carbonic 

 acid, as is evident from innumerable deposits of tufa, and stalactitic forma- 

 tions ; — while the rocks themselves are of limestone: — near Sansadhdrdy 

 6ulphur and sulphuretted hydrogen impregnate the waters, and it is at 

 least plausible to suppose from the occurrence of gypsum, that the 

 presence of sulphuric acid is one, if not the main cause of the super- 

 abundance of carbonic acid diffused through all the springs, and leading 

 to the tufaceous and stalactitic deposits of lime that not only appear 



