

1867.] With the supply of water to Calcutta. 133 



Phosphoric acid : very distinct indications of in both. 

 This was also found in smaller quantity in the other four of these 

 waters, and in still smaller quantity in the water of the aqueduct. 



The relative proportions of these constituents, so different from those 

 of ordinary spring or even river waters, point clearly to their origin. 

 The large quantity of alkaline salts, compared with those of Lime and 

 Magnesia, and the large proportion of Potash and of organic matter, 

 indicate that they are derived from the decomposition of vegetable 

 and animal substances : the phosphoric acid and perhaps the chlorine 

 being more particularly characteristic of their animal origin. In fact, 

 it is the composition of sewage water, and differs from some other 

 analyses of English town sewage* most remarkably in the large 

 proportion of potash present, no doubt the product of the vegetable 

 food of the mass of the population. It is indeed simply sewage water, 

 deprived in great part of its bad smell by filtering through the earth. 

 And the partial analyses of the other tanks and wells (except the 

 three first tanks of the table) indicate that the waters all partake 

 more or less of the same character, and contrast strikingly with the 

 superior purity and different characteristics of the river water during 

 the cold season. 



The large quantity of Ammonia as exhibited by Table VIII. in the 

 two waters fully analysed is also very striking. 



Nov^to return to the consideration of the organic matter which has 

 undergone comparatively little change, and for the proper examination 

 of which we have no very ready or suitable chemical processes : the best 

 means of judging of its nature and properties have already been 

 discussed in my first paper. These are, chiefly, the general appearance 

 and smell of the residue obtained by evaporating the water, the 

 smell on burning, and the estimation of the amount of nitrogen by 

 the Soda lime process. This last, for reasons already stated, I have not 

 applied. But I may observe again, that these bad tank waters more 

 resemble the river water of the rains than of the hot season, in the 

 appearance and properties of their organic contents. No doubt this 

 proceeds in part from the larger proportion of matter of vegetable 



* Lawes and Gilbert, Journal of Chem. Soc. Ser. 2, Vol. IV. p. 118 for 1866. 

 Way's Report on Sewage of Towns quoted in Parkes's, Manual of Practical 

 Hygiene, 2nd edition, 1866, p. 325. 



