1867.] with the supply of water to Calcutta. 117 



other, it may be by some conventional plan or according to some 

 favourite theory, and represent them in the state of neutral salts. 

 And as each chemist may follow his own particular plan, the same 

 analysis may be represented in very different ways. As it is simply 

 impossible to say in what way the acids and bases are united to one 

 another in solution, it is very much better to state them separately ; 

 and I was glad to find that Professor Dr. W. A. Miller expressed the 

 same opinion in bis paper formerly referred to. But for general 

 purposes a full statement of each constituent is unnecessary, and when 

 numerous samples have to be examined, is very laborious. It is 

 generally sufficient to classify them, or select a few of tbe most 

 important and characteristic constituents or properties. In the case of 

 tbe mineral constituents, their total amount, the ojuantity of chlorine 

 or of sulphuric acid, the proportion of earthy salts, that is, of lime and 

 magnesia to tbe alkaline salts, are, singly or together, all more or less 

 suitable according to the nature of tbe water to be examined. The 

 soap test formerly noticed is a very favourite method, from the ease of 

 its execution. I have applied it in some cases, thougb the nature of 

 my enquiries led me generally to have recourse to other metbocls. 



The following table gives a view of the constitution of the river 

 water at the various seasons, classified in a way that seems to me very 

 suitable for comparing different samples. The principal mineral 

 constituents are the alkalies, potash and soda, and the earthy, lime and 

 magnesia, — soda being the most abundant alkali, and lime the principal 

 earthy constituent. These bases are combined with carbonic acid in 

 much the larger proportion, and in smaller proportion with hydro- 

 chloric acid, sulphuric acid and perhaps organic acids. The carbonates 

 of lime and magnesia are kept in solution by excess of carbonic acid, 

 and when the water is boiled or evaporated to dry dryness, by far the 

 greater part, indeed all except a very little of the lime and magnesia, 

 are separated insoluble. These remarks apply to the river water 

 proper ; during the hot season, when tidal influence prevails, the 

 constituents of seawater make their appearance ; then sulphuric acid 

 is increased a little and magnesia still more ; and hydrochloric acid 

 and soda (or chlorine and sodium as common salt) arc largely increased 

 in quantity. 



