1866.1 to&h the supply of water to OalcvMa, 215 



water proper, the mean indeed being nearly as much as tlie maximum 

 of the Hoogbly before tidal influence begins. The amount of variation 

 is much smaller in these waters : of the Thames water the highest 

 quantity of solid matter was 32.62 grs. the lowest 18.78, and the well 

 waters vary less. And it was observed that the quantity of solid 

 matter tended to increase alter heavy rain fall. 



Oilier river waters contain more or less of such constituents, dependent, 

 on the nature of the rocks and soil they traverse. Mr. Sterry Hunt 

 gives an analysis of tin; Ottawa water, taken before the melting of the 

 snows, containing G. 12 grs. solid in 100,000. Bisckoff, in his Chemi- 

 cal Geology, gives a pretty large list of analyses of river waters, show- 

 ing a variation of from 2.61 to 54.5 grains solid matter in 100,000. 

 The nature of their mineral constituents also varies greatly, but that 

 ■will not engage our attention at present as it is more a geological 

 question than a sanitary one. "We shall proceed to the point more 

 immediately connected with the object of the paper. 



The substanees treated of can scarcely be called impurities with 

 reference to natural waters. They are rather constituents, and are 

 only to be considered impurities in a sanitary point of view when 

 they are excessive in quantity, as for instance exceeding 40 or even 

 50 grains in 100,000. The remaining substances to l»e noticed may 

 in a purely chemical point oi view be called constituent! also with 

 quite as much truth, but with reference to sanitary considerations 

 may with propriety be termed impurities. They were enumerated 

 before as organic matter, ammonia and nitric acid. It may be better 

 to consider them as organic matter of vegetable origin and organic 

 matter of animal origin, with the respective products of their decom- 

 position. 



Vegetable substances of all kinds mixed with the soil, exposed to 

 air and moisture or immersed in water, dead animal bodies of every 

 variety in similar circumstances, all rotting, fermenting and putrefying, 

 ■with the excrcmentitious matters from living animals, constitute the 

 materials from which river water derives that portion of its consti- 

 tuents called organic matter. Its nature is so heterogeneous and its 

 quantity so small, that it would be hopeless to attempt to separate it 

 into its proximate constituents. All we can attempt is to get some 

 general idea of its nature, from which to form some judgment of its 



27 



