1866.] with the supply of water to Calcutta. 213 
Macnamara’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 
15.4 of earthy. Or, asI 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. Ido not intend to give any of my own 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 gay 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 soda, 
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 asmuch. 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. 
