Use of Town Sewage as Manure. 
141 
the scwaf2;c of a town i lb. of solid and 3 lbs. of liquid excre- 
ment. Let us next endcavoui* to ascertain, approxirnatelj at 
least, what the composition of these is likely to be. 
The composition of the excrements of different individuals 
varies even more widely than its quantity, beinjj; dependent upon 
age, diet, occupation, and a variety of other circumstances. It 
would be impossible, therefore, to fix with any degree of accuracy 
the average composition in such very variable conditions. We 
may, however, form a general notion sufficient for our purpose 
from the facts which are known on this head. 
Human fa'ces consist partly of the undigested food which has 
been taken in excess over the necessities of the stomach and 
system, and partly of those undigestihle portions, such as woody 
fibre, which, being part and parcel of the food, are necessarily 
taken into the stomach with it, but which pass unchanged out of 
the body in the faeces. In addition to these substances, the 
faeces contain a certain quantity of fatty matter and bile, but 
these do not sensil)ly contribute to its value in relation to agri- 
cultural applications.* 
The most important constituent of human faeces in respect to 
manure would undoubtedly be the nitrogenous matter contained 
in it. We have no certain data for arriving at this point. In 
three samples of excrements mentioned below I found respec- 
tively a percentage of 1*44, 1"16, and 1"45 nitrogen ; which, 
* Many years ago the great Swedish chemist Berzelius made a very careful 
examination of human fiEces. AVithout entering into details, the following may 
be given as the general result of his analysis (Thomson's Animal Chemistry, 
p. 544) 
In 100 parts- 
Water 73 "3 
Vegetable and animal remains 7*0 
Bile 0-9 
Albumen 0-9 
Peculiar and extractive matter 2*7 
Salts 1-2 
Slimy matter — consisting of biliary matter, peculiar 
animal matter, and insoluble residue . . . . 14*0 
100-00 
I have lately determined the percentage of nitrogen in several samples of human 
excrement. The following table contains the results, together with the propor- 
tions of water and solid matter in the samples which have been already referred 
Mean 
Quantity 
Voided. 
Water. 
Dry Matter. 
Nitrogen 
in 
the Wet. 
Nitrogen 
in 
the Dry. 
A 
Grains. 
1413 
Per Cent. 
74-27 
Per Cent. 
25-73 
Per Cent. 
1-44 
Per Cent. 
5-59 
B 
1344 
73-24 
26-76 
1-16 
4-34 
C 
1198 
79-60 
20-40 
1-45 
7-13 
