10 REPORT— 1880. 



paratively rainless countries salts are often deposited on the surface of the 

 ground by the effect of solar evaporation of moisture from the soil. "Water 

 dissolves certain salts in combination with the ingredients of the under- 

 lying rocks and soils, and brings it to the surface, and when solar evaporation 

 ensues the salt or salts are deposited on the ground. This is well known 

 to be the case in and near the region of the Great Salt Lake in North 

 America, and in South America in some of the nearly rainless districts of 

 the Cordillera, extensive surface- deposits of salts of various kinds are 

 common. The surface of the ground around the Dead Sea is also in extra 

 dry seasons covered with salt, the result of evaporation, and in the upper 

 provinces of India (mentioned by Medlicott and Blanford) ' many tracts 

 of land in the Indo-Gangetic alluvial plain are rendered worthless for cul- 

 tivation by an efflorescence of salt known in the North-West Provinces as 

 Reh,^ while every geographer knows that in Central Asia, from the western 

 shore of the Caspian Sea to the Kinshan Mountains of Mongolia, with 

 rare exceptions nearly every lake is salt in an area at least 3,500 miles in 

 length. This circumstance is due to the fact that all so-called fresh-water 

 springs, and therefore all rivers, contain small quantities of salts in solu- 

 tion only appreciable to the chemist, and by the constant evaporation of 

 pure water from the lakes, in the course of time, it necessarily happens 

 that these salts get concentrated in the water by the effect of solar heat, 

 and, if not already begun, precipitation of solid salts must ensue. 



The earliest deposits of rock-salt that I know about have been described 

 by Mr. A. B. Wynne of the Geological Survey of India, in his Memoir ' On 

 the Geology of the Salt Range in the Punjab.' ' The beds of salt are of great 

 thickness, and along with gypsum and dolomitic layers occur in marl of a 

 red colour like our Keuper Marl. This colour I have for many years con- 

 sidered to be, in certain cases, apt to indicate deposition of sediments in 

 inland lakes, salt or fresh, as the case may be, and with respect to these 

 strata in the Punjab Salt Range, authors seem to be in doubt whether 

 they were formed in inland lakes or in lagoons near the seaboard, which 

 at intervals were liable to be flooded by the sea, and in which in the hot 

 seasons salts were deposited by evaporation caused by solar heat. For my 

 argument, it matters but little which of these was^the true physical con- 

 dition of the land of the time, though I incline to think the inland lake 

 theory most probable. The age of the strata associated with this salt is 

 not yet certainly ascertained. In ' The Geology of India ' MedHcott 

 and Blanford incline to consider them of Lower Silurian age, and Mr. 

 Wynne, in his ' Geology of the Salt Range,' places the salt and gypsum 

 beds doubtfully on the same geological horizon. 



The next salt-bearing formation that I shall notice is the Salina or 

 Onondaga Salt Group of North America, which forms part of the Upper 

 Silurian rocks, and hes immediately above the Niagara Limestone. It is 

 rich in gypsum and in salt-brine, often of a very concentrated character, 



* Many earlier notices and descriptions of the Salt Range might be quoted, but 

 Mr. Wynne's is enough for my purpose. 



