342 Scientific Proceedings, Royal Dublin Society. 
The sample was taken from much the same part of the stream 
as sample No. 2, and also one foot below its surface. 
The dissolved gases and other significant constituents were 
determined on the day of collection, and a portion of the 
sample was preserved out of contact with air for a period of 
four days, and again examined. 
The results obtained were as follows :— 
N as N as N 
Date. CO, | O, | Nz NH, N.O. N,0, 
| 
April 20,1894, . . .| 119-26 5:98 16°44 0009 | :00018 | -00952 
April 24, 1894, . . .| 120°56 5°32 16°38 001 00012 | -009388 
Differences, | + 1°30 | — -66 
The sample was slightly turbid, practically colourless, and contained 
no suspended matters. It was neutral. When first collected it 
yielded :005 grms. N as albuminoid ammonia per 100,000 c.es. 
of water. 
These results show that even during the comparatively long 
period of four days, only -66 c.cs. of oxygen out of a total of 
5:98 c.cs. per litre were consumed. Had considerable quantities of 
fermentable organic matters been present in the water, there can 
be no doubt, from the experiments recorded in my first Paper, 
that the oxygen would have been absorbed in a few hours after 
fermentation had set in. 
It will be noted that the time given for fermentation, in 
the case of samples Nos. 1 and 2, was seven and eight months, 
respectively. This length of time was not necessary, but was 
unavoidably allowed for the reason I have already stated. 
In a neutral water containing so small a quantity of fer- 
mentable organic matter as each of these two samples, the time 
necessary for the first stage fermentation, judging from experiments 
recorded in my first Paper, would not exceed one month ; and that 
required for the completion of the two stages, the final result of 
which would be the complete oxidation of all ammonia present, 
would not exceed two months. 
Ineed scarcely dwell upon the great power which this new 
