42 LA TOL'CHE : GEOLOGY OF WESTERN RAJPUTANA. 



Sambhar and Didwana. The water of wells that are sunk in the 

 sand without reaching the rock beneath is also brackish as a rule, 

 and sometimes decidedly salt. Mr. Blanford conjectured that the 

 salt may have been derived from an arm of the sea which, he supposed, 

 formerly extended up the valley of the Luni, 1 but there are consider- 

 able difficulties in the way of accepting this theory. In the first place 

 there is no evidence whatever of a recent submergence and re-eleva- 

 tion of the desert area, such as would bring the Sambhar lake down 

 to sea level, and back again to its present position 1,184 feet above 

 the sea. This objection was pointed out by Mr. Blanford himself. 

 Again, if the sea only extended as a gulf up the lower portion of the 

 Luni valley, this would not account for the presence of salt higher up 

 the valley ; and in any case such a gulf, if it ever existed, would be 

 filled up by ordinary silt brought down by the rivers from the hills, 

 and not more likely to contain salt in larger quantities than similar 

 sediments elsewhere. 



It seems to me that instead of our being compelled to speculate 

 on former extensions of the sea or great changes of level, no evidence 

 of which is to be found, in order to account for the presence of the 

 salt, a simple explanation presents itself in the peculiar conditions of 

 the country as regards drainage and evaporation. The rain water 

 flowing from the hil's is evaporated long before it reaches the sea, 

 owing to the porous nature of the sand and the dryness of the atmos- 

 phere, and the salt it contains, which would under ordinary condi- 

 tions be carried by rivers itto the sea, and help to swell the amount 

 of salt already there, is deposited among the sand grains, and" in 

 process of time has thoroughly impregnated the soil with salt. The 

 process is in fact exactly similar to that which, it is universally- 

 admitted, accounts for the presence of the salt in the sea itself. 

 Wherever depressions in the general level of the country occur, as at 



1 Journ. As. Soc. Beng., Vol. XLV, Pt. 2, p. 96. Rec. Geol. Surv. Ind., Vol. 

 X, Pt- 1, p. 21. 



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