144 
Use of Town Sewage as Manure. 
ingredients of urine. From a calculation given below,* it will 
be seen that 1000 grains of urine contain about IJ grains of 
phosplioric acid, wJiich is equal to about 2i grains of phosphate 
of lime ; but, as in the other cases, this quantity varies so ex- 
tremely that the result is only to be taken as an approximation 
to the truth. It is obvious that healthy urine contains, when first 
voided, only matters in a state of solution. In certain diseases 
there is, it is true, a deposit after a short time ; but such is the 
exception, not tlie rule. The phosphoric acid of urine is in part 
combined with soda, ammonia, &c., in the form of soluble salts. 
Some of it, however, is in the form of phosphate of lime, itself 
an insoluble salt, but retained in solution in fresh urine by organic 
acids. But with this exception, all the salts of urine, the sul- 
phates and muriates of potash, soda, and magnesia, are soluble 
in water, and do not owe their solubility in fresh urine to its 
acid character. These particulars it is important to bear in mind, 
as they have an immediate bearing upon the question of the agri- 
cultural employment of sewage, as we shall presently see. 
With a general knowledge of what the constituents of urine 
and faeces respectively are, let us see what relation in quantity 
those that are most important in an agricultural point of view 
bear to each other in the solid and liquid excrements. 
We have adopted 1750 grains as the mean quantity of solid 
excrement voided in 24 hours ; at a percentage of 1*5 of nitrogen 
(see analysis in note, page 141), which is certainly above rather 
than behiw the truth, we liave as the total nitrogen in this quantity 
26t grains. The excrement contains l-4th of its weight of dry 
matter, or 437t gi'ains. 
In 21,000 grains (three pints) of urine voided in 24 hours, we 
have, on the supposition that each 1000 grains contains 295- grains 
of dry solid matter, 619^ grains of solid matter voided in tlie 
same space of time. Of this quantity 261 is urea and 10 grains 
uric acid, which will contain between them 125 grains of nitrogen. 
It may serve to impress the mind with the full conviction of this 
relation if these figures are placed in a tabular form : — 
Coiitaiuing — 
Dry Matter. Nitrogen. 
SoHd excrement, voided \ 1750 srrs. „„, 
in 24 hours . . ./ Ulb. ^^71 grs. 26^ grs. 
Liquid excrement, voided) 21,000 fiioi ^nK 
in 24 hours . . . i(3 pints) ^-^'^ " " 
So that in reference to the solid matter and nitrogen of the faeces 
* Thomson gives the quantity of phosphoric acid in lOUO parts of urine as 
follows : — 
In the state of phosphates of soda, ammonia, &e. . 1 • 1.31 
In the state of phosphate of lime . . . '150 
Total . . . .1-281 
