Reviews — Indian Salt Deposits. 269 



highly charged with sodium chloride, which is raised for the 

 purpose of manufacturing salt at various places. The largest of 

 the lakes is at Sambhar, which, when filled with water at the 

 end of the rainy season, covers, according to the season, from 

 70 to 80 square miles, and with the latter area may reach a depth 

 of only four feet in the centre of the lake". Since 1869 this 

 lake has been "one of the principal sources of salt in Northern 

 India, the output being on an average about 140,000 tons a year ". 

 About ten years ago it was thought that the resources of the lake 

 might be diminishing, but investigations and borings made by the 

 Geological Survey of India demonstrated "the occurrence of 

 something like 54 million tons of salt in the uppermost 12 feet of 

 silt ", and anxiety was relieved. 



After discussing various theories propounded with regard to the 

 origin of the salt, Sir Thomas Holland points out that during the hot 

 dry season large areas of the Uann of Cutch become covered with an 

 incrustation of salt. During the same period, from April to June, 

 dry, hot, and strong winds and gales blow from the south-west and 

 carry away great quantities of the dry and powdery salt to the 

 liajputana Desert. When the rains set in the salt at and near the 

 surface is carried in solution by the floods into the hollows which 

 become temporary lakes, and after the rainy season is over there will 

 be areas of concentrated brine, with or without complete evaporation, 

 during a cold dry period. These conditions are succeeded by the hot 

 season and by further supplies of salt-dust carried by the south-west 

 winds. Observations and experiments carried on by Sir Thomas 

 Holland and Dr. Christie have led them to conclude that at least 

 200,000 tons of salt aie thus annually distributed over the Eajputana 

 Desert. 



Attention is drawn to the observations of the late J. Lomas on the 

 features common to the Trias and to modern desert formations. 

 Among these explanation is given of the occurrence of pseudomorphs 

 of rock-salt and of the nature of the so-called red marls, which 

 consist largely of very fine particles of quartz dust. It is noted that 

 the silt of Sambhar consists locally of large accumulations of the 

 finest mud of a deep-black colour, due to the presence of ferrous 

 sulphide, and it is suggested that the red colour of the mudstones 

 or so-called marls of the Trias are equivalent deposits, their colour 

 being due to the subsequent oxidation of the iron-salt. 



With respect to the bearing of wind-borne salt on estimates of 

 geological time, the author supports the conclusions of Professor Joly 

 and others concerning " the relative unimportance of such cyclic 

 sodium in calculations regarding the rate of accumulation of salt in 

 the ocean ". 



Y. — Geological Sukvey of Westeen Austkalia. 



IN Bulletin No. 45, 1912, Mr. H. W. B. Talbot deals with parts 

 of " The North Coolgardie and East Murchison Goldfields ", giving 

 the results of a series of traverses made in' company with Mr. C. S. 

 Honman, the Topographical Surveyor. The report is illustrated by 

 a geological sketch-map of the country around Lake Barlee (scale 



