CHEMICAL ANALYSES. 280 



Assuming then that sodium sulphate is formed in the manner 

 suggested by Schweinfurth and Lewin (see above), we have to 

 consider whether the peculiar conditions in the Sind desert favour 

 the further transformation of sulphate into carbonate by bacterial 

 action as Sickenburger supposes is the case in Egypt. 



The following points seem to be of importance in this connec- 

 tion : — 



(1 ) The alkaline dhands derive their water supply invariably 



from sim or percolating water coming from beneath the 

 desert sand. 



(2) The soil associated with this sim water is of a very dark 



colour, and has a carbonaceous appearance. 



(3) The alkaline dhands have a peculiar and offensive smell 



and in this respect differ markedly from the saline 

 dhands. 



(4) They contain bacteria of a peculiar type. Specimens of 



the bitterns were taken by me in December 1918. placed 

 in spring stoppered bottles with rubber fittings (and 

 therefore air-tight),, and sent to the Geological Survey 

 Laboratory for testing. With the exception of an hour 

 or so, when the bottles were opened in order to take 

 out samples for testing, they were kept air-tight till 

 September 1919,— a period of eight months. Never- 

 theless the bacteria were still vigorous, and were found 

 still living in such strong bitterns as Mithri and others 

 of similar high specific gravity. The discovery of 

 bacteria in these bitterns is due to Dr. Annandale, who 

 kindly examined several bottles. Captain li. S. Sewell, 

 I. M.S., also kindly examined some samples for me. The 

 bacteria appear to be anaerobic, but they have not been 

 identified with any known type, and it would be exceed- 

 ingly interesting to study them further. I am not 

 myself qualified to undertake this, but I hope at some 

 future time that the matter may be investigated by a 

 bacteriologist. 

 I then seek an explanation of these alkaline dhands in the peculiar 

 conditions of the Sind desert, where a flat alluvial plain, probably 

 fertile formerly (or at any rate as fertile as the plain west of the 

 Nara), is now completely covered by wind-blown desert sand. The 

 alluvial clay is fairly impervious to water. This is a feet well 



