AprnEY— The Reservoir at Roundwood. 211 
water is well under the limit usually allowed to a good potable 
water; that, however, in the unfiltered water, just exceedsit. A 
careful examination, however, of the analytical data given in the 
above table will, I think, lead to the conclusion that the organic 
matters in both unfiltered and filtered water may be classed as un- 
fermentable, and may, in consequence, be regarded, both from 
experience and our present knowledge, as presenting no danger to 
health. 
Let us consider, in the first instance, the filtered water. The 
fact that the very decided quantity of free ammonia in the unfiltered 
water became practically completely oxidized to nitric acid during 
the passage of the water through the filter-beds proves that the 
water had undergone a very strong process of oxidation, one, in 
fact, which warrants the conclusion that all fermentable organic 
matters, if any were present in the unfiltered water, must have been 
completely oxidized. ‘This conclusion is warranted by the results 
of all bacteriologists and chemists who, so far as I am aware, have 
made the products of destructive metabolism of saprophytic organ- 
isms a special study. ‘Their results all tend to show that, with all 
fermentable organic matters, when dissolved or mixed with water, 
and exposed to the influence of saprophytic organisms, the organic 
carbon becomes first oxidized, chiefly to carbon dioxide, the oxida- 
tion of the carbon in nitrogenous matters being usually attended 
with the formation of ammonia and other substances. From a 
large number of experiments I have made on this subject, I have 
found that the ammonia so formed, or purposely added, only begins, 
under ordinary circumstances, to suffer oxidation after most of the 
organic carbon has been oxidized, and then, and not till then, does 
the ammonia begin to become oxidized. When nitrification has 
set in, then the amount of ammoniacal nitrogen oxidized may much 
exceed in proportion the amount of organic carbon simultaneously 
oxidized to carbon dioxide. 
The question then arises, what is the character of the organic 
matters left in the water after they had passed such a strong 
process of oxidation as that we have seen to be exerted by the 
organism in the surfaces of the material composing the filter-bed ? 
There can be no doubt that the remaining organic matters were 
either derived from peat, or are similar in character to the colour- 
ing matters found in peat. 
