23 



and 0.16; and in August last gave 0.125 albuminoid nitrogen per mil- 

 lion. ^Ve must not forget that these are English standards and on that 

 account are questionably api)licable to American rivers, which flow for 

 very great distances over forest and marshy regions where contamination 

 by sewage — \n the ordinary acceptance of this term — cannot occur. 

 We must, I think, concur in the wisdom of Prof. Mallet's decision thaj- 

 " local standards of purity should be ado])ted, based on sufficiently 

 thorough examination of the water-supply in its usual condition. 

 Unfortunately no systematic and continuous examination of our city 

 supply has yet been undertaken, and it is impossible for me to state, 

 except in a very imperfect way, what the normal composition of the 

 Ottawa water is. It must, of course, be expected to vary for different 

 months ; but we should have a series of analyses made at weekly inter- 

 vals for a number of years ; and from the averages so obtained it would 

 be a simple matter to determine the mean character of the water for 

 any period. When we consider that water is a universal food substance 

 that it enters into the preparation of every article of food ; that from the 

 nature of its production and storage, it is peculiarly liable to contamina- 

 tion in vatious ways, and that the most fatal diseases have been fully 

 proven to have become epidemic, through its agency, we shall, I think, 

 agree that a constant and careful examination of the su[)ply uf a city 

 like ours is but a reasonable and necessary precaution. 



9. When organic matter containing nitrogen has been exposed for 

 a sufficiently long time to the ameliorating influences that are always 

 at work in nature, the nitrogen takes the form of nitric acid, and when 

 this is once formed and enters into combination with bases as nitrates, 

 the condition of the nitrogen is fairly stable, and the nitrates so formed 

 may exist as such for an indefinite length of time. Complex organic 

 substances like albumen are thus changed into simple inorganic sub- 

 stances, perfectly harmless, and only interesting to the analyst as serving 

 to measure the previous sewage contamination of the supply. For 

 where much sewage has found entrance to a well-water, for example, 

 although little or none may be now present as sewage, the telltale 

 nitrates serve to prove past contamination. I need scarcely say that 

 such wells as those quoted below are undoubtedly infected by 

 sewage : — 



