338 Scientific Proceedings, Royal Dublin Society. 
The most striking feature of this table is the evidence afforded 
of the great rapidity of the changes which occurred in the first 
series of experiments compared with those which took place in the 
second and third series. In the former about 40 per cent. of the 
dissolved oxygen disappeared in 24 hours, and 60 per cent. in 
48 hours, whereas in the second series only about 7 per cent. had 
isappeared in 88 hours, 14 per cent. in 90 hours, and only 18 per 
cent. in 528 hours (22 days). 
Owing to an accident to the gas analysis apparatus when 
commencing the third series of experiments, the dissolved oxygen 
and nitrogen in the original mixture of sewage and sea-water 
could not be determined ; but if it be assumed that the oxygen 
was about the same as in the preceding series (as was no doubt the 
case), then, in 7 days (168 hours), only 15 per cent. was lost, and 
at the end of 21 days, 26 per cent. 
The composition of the sewage employed is, no doubt, mainly 
responsible for this remarkable difference in the behaviour of the 
mixtures, No. 1 sample being evidently far more concentrated 
than the other two. 
Want of uniformity in the composition of sewage is one of the 
difficulties which must attend experiments of the kind described, 
and it is not easy to see how it should be overcome. 
It is evident that what is really required is a stock of standard 
sewage—say, London sewage, but how could this be preserved ? 
If evaporated to dryness, a stock of putrescible substances of 
uniform composition would, no doubt, be obtained; but they 
would, of course, have suffered considerable changes during evapo- 
ration, and would scarcely be of the same nature as sewage, 
especially as the characteristic bacteria would have been destroyed. 
Another plan would be to experiment, as Dr. Adeney has done, 
with definite substances, such as urea, asparagine, albumen, &c., 
and, no doubt, much light would thus be thrown on the subject ; 
but this method would involve an enormous amount of work, 
as each substance would require separate investigation, both at 
different temperatures and in different concentrations, and it 
might after all be urged that such substances do not represent 
sewage. 
Turning, again, to the Table of Results, the evolution of 
carbonic anhydride—or rather its production—in relation to the 
