64 NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 
In his present letter Mr. Hamilton quotes from “ the letter to Dr. Odling,” 
but the copy of the pamphlet which we read contains no such letter.] 
NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 
On Town Sewage and its Value. 
In February of the present year, a discourse was delivered before the Chemical 
Society, by Dr. Gilbert, “ On the Composition, Value, and Utilization of Town 
Sewage.” The substance of this discourse has been since embodied in a paper 
by Messrs. Lanes and Gilbert, and published in the Society’s Journal.* This 
paper forms a most comprehensive treatise on the subject, and is of considerable 
length, filling 48 pages. In some preliminary remarks on the general position 
of the sewage question, the authors, although admitting the difficulties and 
loss attending the present system of water-purification for towns, nevertheless 
deprecate the idea of returning to any cesspool, tank, or barrel method of col¬ 
lecting excreta, as being inconsistent with habits and notions of cleanliness, and 
with the maintenance of the comfort and health of large populations. They 
moreover show that neither on the Continent nor in this country has such a 
method resulted in any substantial profit to the towns adopting it. Even in 
Belgium, where, it has been stated, the excretal matters sell for something over 
£1 per person per annum, the authors found by personal observation and 
inquiry that in no case did the town population realize as much as averaged 
one franc per head per annum, while the practice of collection and removal was 
attended with much nuisance and discomfort. 
In a chapter on the “ Composition and Value of Sewage,” the authors state 
it is one thing to determine the amount of constituents contained in sewage or 
contributed to it by a given population, and to estimate their value accordingly, 
as if they existed in the dry and portable condition of the various concentrated 
manures of known value in the market; but it is obviously quite another to 
settle the really available or realizable value of the same constituents when they 
are distributed through an enormous volume of water, and if they must be 
transported and utilized in that condition. With this qualification they then 
discuss in detail the means of determining the theoretical value of sewage. 
When the calculation of this value is based on an analysis of the sewage, they 
show that the result may be very simply arrived at as follows:—“If a value of 
8d. be put upon every pound of ammonia shown by analysis to be contained in 
sewage, or if for each grain of ammonia per gallon, a value of one farthing be 
given to the total constituents in one ton of the sewage, the result will in either 
case agree almost exactly with that obtained by the elaborate method of giving 
the currently-adopted market values to the several constituents, taking dry and 
portable manures as the standard.” Thus, in 1865, Liebig assumed the average 
sewage of the metropolis to contain 7*2 grains of ammonia per gallon, and he 
estimated the value of the constituents in 1 ton of such sewage to be rather over 
Ifd. The authors’ estimate would also give rather over 7 farthings, or l|d. In 
1857, Messrs. Hofmann and Witt concluded from their investigations that the 
average dry weather sewage of the metropolis contained about 8*2 grains of am¬ 
monia per gallon, and calculating the value of the sewage according to the 
amount of ammonia, organic matter, phosphoric acid, and potassa, they esti¬ 
mated that of the total constituents in 1 ton of such sewage to be about 2Tld. 
It is clear, that giving a value of \d. to the total constituents per ton of sewage 
* Journ. Chem. Soc. ser. 2, vol. iv. p. 80. 
