o f sewage (1) in alkaline solutions, (2) in distilled water. 355 
In the following table we give the results when the sewage 
was incubated with sea, -water from Stalham, off the Norfolk coast, 
when analyses were made after 1 day, 3 days, and 8 weeks. 
Time 
Free NH :J 
Albuminoid 
nh 3 
Total NEC 
Nitrates and 
Nitrites 
Coni mencement. . . 
0-32 
0-12 
0-44 
absent , 
1 day 
0-40 
0-13 
0-53 
55 
3 days 
0-36 
0-17 
0-53 
55 
8 weeks 
0-32 
0T1 
0-43 
55 
1 
The results were very similar to those in the preceding table, 
and showed (1) that there was a small rise in the total ammonia 
by about the end of the third day and then a gradual fall, and 
(2) that no nitrates or nitrites were produced. 
And in all the experiments Purvis and Coleman conducted 
they obtained similar results. Perhaps the most striking result of 
the experiments was to prove that there was a marked interference 
in the production of nitrates and nitrites when the sewage was 
incubated with the aforesaid salts, both singly and when mixed in 
the proportions in which they are found in sea- water, and also 
when incubated with natural sea-water both sterilised and un- 
sterilised. It appeared as if the dissolved salts interfered with the 
growth of the nitrifying organisms which, under favourable condi- 
tions, rapidly convert sewage into simpler compounds such as 
nitrates. The production of nitrates and the simultaneous dis- 
appearance of the two ammonias are usually considered to be 
measures of the efficiency of any method of sewage disposal. But 
in these experiments there was no production of nitrates or of 
nitrites. The decomposition of the sewage did not extend to 
a complete breakdown into the simple forms of water, carbon 
dioxide, and nitrates. There was a progressive decrease in the 
two ammonias, but highly complex nitrogenous compounds re- 
mained in solution even after a period of 8 weeks incubation. 
It seemed to be of some importance to study the break- 
down of sewage under other conditions than those of Purvis and 
Coleman’s ; and the present writers have conducted a series of 
experiments by incubating sewage (a) with alkaline solutions, and 
(6) with ammonia-free distilled water, of which the following is an 
account. 
