1871.] KAMSAT — PRETRIASSIC RED ROCKS. 249 



other red marls, such as our Keuper beds. Solid dolomite, he goes 

 on to say, still contains " about one-fifth per cent, of salts soluble in 

 water, consisting of chlorides of sodium, magnesium, potassium, and 

 calcium, and sulphate of lime. These, like those in most crystals 

 formed from solution, must have been produced at the same time 

 as the dolomite, and caught in some of the solution then present, 

 which is thus indicated to have been of a briny character." 



There are no solid beds of rock-salt in our Magnesian-Limestone 

 series, though I see no reason why pseudomorphous crystals may 

 not occur in the limestones and associated marls. 



Mr. Sorby speaks of the Magnesian Limestone as having been 

 formed in sea- water ; and I presume he means ordinary open sea. I 

 submit that it may be more probable that all our Permian magnesian 

 limestone was chiefly or altogether formed in an inland salt lake. 

 Under such circumstances it appears to me more likely that carbonates 

 of lime and magnesia might have been deposited simultaneously by 

 concentration of solutions due to evaporation ; for I cannot under- 

 stand how such deposits could have taken place in an open sea, 

 where necessarily lime and magnesia only exist in solution in very 

 small quantities in such a large bulk of water. In the open sea, 

 indeed, we know of the formation of beds of limestone only by 

 means of organic agency. The occurrence of gypsum in the marly 

 strata of the Magnesian-Limestone series helps to this conclusion. 

 I have also observed in some of the lower strata of the Mag- 

 nesian Limestone, when weathered, that they consist of a number 

 of curious thin layers bent into a number of very small convolutions 

 approximately fitting into each other, like a number of sheets of 

 paper crumpled together, and conveying the impression that they are 

 somewhat tufaceous in character, looking almost stalagmitic, as if 

 the layers, which are unfossiliferous, had been deposited from solu- 

 tion, and not like ordinary organic calcareous sediment. 



In'an elaborate disquisition on dolomites, in two lectures. Dr. Percy 

 concludes with the following words : — " That dolomite has been 

 formed by the agency of liquids under very ordinary conditions, I 

 have little doubt will be hereafter fully established by direct and in- 

 disputable chemical evidence" *. In the ' Geology of Canada ' (Logan) 

 Dr. Sterry Hunt has given the results of his chemical investigations 

 bearing on geology, in chapters 17-20. At pp. 575-6 he discusses 

 the subject of dolomites. The passages are too long for quotation ; 

 but after explaining various natural processes by which he conceives 

 that mixed carbonates of lime and magnesia may be deposited from 

 solution in salt water, he concludes that " these reactions require in- 

 land seas, or basins cat ofi^from communication with the ocean, while, 

 on the other hand, the conditions of the production of carbonate of 

 lime are everywhere found." The chemical arguments are not what 

 first led me to suspect that the Permian magnesian limestone was 

 deposited in an inland salt sea from solution, though I soon after 

 began to entertain the idea, and to search for evidence on the point. 

 It is satisfactory to find that eminent chemists take this view with 

 * Swiney Lectures, 1864, ' The Chemical News,' p. 89. 



