1866.] with the supply of water to Calcutta. 213 



Macnaniara's report, in the month of August there was in 1 gallon of 

 water 1.2 grains of soluble salts and 5.4 grs. of insoluble earthy salts, 

 beside silica and organic matter, and in February 1.8 of soluble and 

 13.4 of earthy. Or, as I prefer to express it, there was in August 1.7 

 grs. alkaline salt and 7.8 grs. earthy carbonates in 100,000 fl. grs., and 

 in February 2.6 alkaline salt and 19.1 grs. earthy carbonates in the 

 same volume. The first represents the water in its most diluted state 

 during the height of the rains, the last in its most concentrated state 

 at the end of the cold season, just before tidal influence begins to be 

 felt. I do not intend to give any of my oavu results, partly because a 

 full analysis of the water is not the object of this paper, and partly 

 because a circumstance entirely unforeseen and unexpected has thrown 

 doubts on the correctness of some of those obtained, and I do not 

 wish to give them in an imperfect state, as they cannot be corrected 

 until the return of the cold season gives me a new supply of water. 

 It is sufficient to say that they do not appear to differ materially 

 from those given in Dr. Macnamara's report. The only point to 

 be noticed is, that Dr. Macnamara, in accordance with the usual custom, 

 where minute accuracy is not required, assumes that the alkali is s<nla. 

 Both potash and soda, however, are present in the river water ; to what 

 extent they vary, I have not yet ascertained. During the hot season, 

 from the increase of common salt from tidal water, there is of necessity 

 a great increase in the proportion of soda in the state of common salt. 

 The^ alkaline salts consist of potash and soda in combination with 

 sulphuric acid, silicic, and probably hydrochloric acid (or more strictly 

 their metals combined with chlorine) and perhaps some organic 

 acid. The earthy salts are carbonates of lime and magnesia, kept in 

 solution by excess of carbonic acid. On evaporation nearly the 

 whole of the lime and magnesia separate as carbonates insoluble. 

 Besides these there are a few minute constituents to be noticed after- 

 wards. The only"' particular now to be noticed is, the different 

 proportion of solid constituents in the water at the two extremes ; in 

 August there is 9.5 grains of alkaline and earthy salts in solution in 

 100,000 fl. grs. of^water, in February there is 21.78 grs. or about two 

 and a quarter times as much. This great difference is of course due to 

 the nature of^the seasons'in Bengal, where almost all the rain falls 

 during four or five continuous months. 



