354 A. B, WYNNE ON THE PHYSICAL 



the Himalayan area, while in the Salt-Range region there was an 

 enormous accumulation of gypseous marl taking place, in which 

 stratification is seldom observable, unless marked by the occasional 

 presence of layers of gypsum or dolomite, or towards the top by 

 the thick bands of gypsum and rock-salt. Over these, sandstones 

 were laid down, succeeded by dark-coloured mud and calcareous 

 glauconitic layers, deposited by waters which contained, at least, 

 some forms of organic existence (Obolus). 



7. The mystery in which the origin of rock-salt is involved makes 

 it difficult to imagine why this old deposit should be limited to the 

 narrow area of the Salt Range and a few miles beyond the Indus. 

 How far it may extend beneath the Rawal-Pindi plateau it is im- 

 possible to say, but that it does not very suddenly die out seems 

 likely from the occurrence of the salt-marl and saline springs in 

 faulted exposures on the north of the range. I have estimated that 

 there is in the neighbourhood of the outcrop, roughly speaking, a 

 quantity of the mineral equal to nine cubic miles, or in round 

 numbers enough to represent all the salt of a body of sea-water 

 half a mile deep and 700 to 800 square miles in superficial 

 extent. 



The mode in which the salt occurs is in simple alternations of 

 thick pure translucent bands, with other thick bands containing a 

 large proportion of clay. The stratification of the salt is well 

 marked, even in the purest bands, by numerous laminre of different 

 texture or colour • and it shows the effects of disturbance in the 

 same way as other stratified rocks, by inclination and curvature. 

 The thick beds of pure gypsum, as a rule, overlie it. No visible 

 foreign matter, except the clay*, enters into the composition of 

 either of these rocks ; but both have sometimes a blotched or 

 brecciated look, produced by more compact or more crystalline 

 lumps, in the case of the salt lying in a more earthy matrix. 



With regard to the supposition that this enormous deposit of rock- 

 salt may be attributed, as is usually done, to the evaporation of an 

 isolated salt-water lake, lagoon, or backwater, I am unacquainted 

 with any instance of the recent formation of salt in this manner 

 which does not become insignificant when compared with the 

 hundreds of feet of solid salt accumulated at the Salt Range, or in 

 the other salt region of this country. The recent deposits of Carmen 

 Island, and those taking place round the shores of the Caspian, may 

 be larger or deeper than those of the Run of Kutch, for instance ; 

 but I have been unable to obtain a record of their thickness f or the 

 depth of their basins. 



Even if the seas of the period were more saline, or evaporation 

 more rapid, it appears that neither of these conditions would account 

 for the observed association of gypsum with and overlying the rock- 

 salt. 



It is strange that the only igneous rock found in situ in the Salt 



* And in rare instances iron pyrites or quartz in small crystals in the gypsum. 

 t The Caspian deposits are treated of in Yon Baer's papers, Bulletin de 

 1'Academie Imp. des Sciences de St. Petersbourg, vols, xiii., xiv., xv. 



