^s'OTES AND ABSTEACTS IN CHEMISTRY AND PHARMACY. 65 
for each grain of ammonia per gallon, would yield almost identically the same 
result. 
The authors quote a number of analyses which have been made of metropo¬ 
litan sewage. The results show a variation of from about 3 to more than 41 
grains of ammonia per gallon. This variation is due to the unequal dilution to 
which sewage is subject. The authors consider that the sample analysed by 
Messrs. Hofmann and Witt (containing 8-2 grains of NHg per gallon) repre¬ 
sents the average dry iveather sewage of the metropolis better than any previously 
collected and examined. It was a mixture of equal portions taken every hour 
during 24 hours of dry weather, and the constituents in 1 ton were estimated 
to be worth rather over 2d. According to information furnished to the analysts, 
the quantity of such sewage (^. e. sewage exclusive of rainfall) was calculated to 
be about 158,000,000 tons per annum. 
The authors next describe the series of experiments which were made at 
Rugby, from which they conclude that from that town there are, on an aver¬ 
age, about 60 tons of sewage per head per annum, containing 6^ grains of am¬ 
monia per gallon.^' From this it would result that 12^ lbs. of ammonia were 
contributed annually for each average individual of the mixed population, of 
both sexes and all ages. 
The authors then discuss another method which has been adopted for com¬ 
puting the value of sewage, namely, by the calculation of the amounts of fseces 
and uATire, or of the various constituents of these, voided by persons of different 
sexes and ages, 'in 1854, the authors, basing their estimates on very compre¬ 
hensive data, relating both to the amounts of constituents consumed in the 
food and voided in the urine and fseces, of persons of different ages and both 
sexes, concluded that probably about 10 lbs. of ammonia, and total constituents 
of the estimated manurial value of about Qs. 8(f., were annually contributed to 
aewage per individual of a mixed town population. More recently they have 
revised their estimates, and reviewing the whole of the evidence they have con¬ 
cluded that the amount of ammonia annually contributed to the sewer-water by 
an average person of a mixed population was pretty certainly more than 10 lbs., 
as formerly assumed, but probably less than 12 lbs., and making allowance for 
the fractional part of the excretal matters of horses, cows, dogs, and other ani¬ 
mals, of the refuse of slaughter-houses, of soot, and of other refuse matters that 
may reach the sewers, it was concluded that still not more than 12| lbs. of am¬ 
monia would be contributed annually to the sewers from all sources per head of 
mixed town population. This would indicate an estimated value of 8s. 4zd. per 
annum for the total constituents in the sewage for each average individual. 
Since the publication of this last estimate, however, numerous gaugings of the 
mid- and high-level northern sewage have been made, and many samples have 
been analysed by Mr. Way. Although these results are not yet published, the 
authors are enabled to state their general bearing. They appear to indicate 
that the total amount of dry weather sewage averages only about two-thirds 
as much per head as that assumed by Messrs. Hofmann and Witt, but that the 
amount of ammonia per gallon agrees with their estimate. It would follow 
from this that the amount of ammonia annually contributed to the sewage, 
from all sources, per head of a mixed population, is more nearly 10 lbs. than 
12| lbs. We have then from 10 to 12|lbs. of ammonia, and an estimated value 
of from 6.9. 8d. to 85 . 4zd. for the total manurial constituents contributed to 
sewage by each average individual of a mixed town population. The actual 
amount of fluid per head per annum, is calculated to be about 80 and certainly 
not exceeding 100 tons, inclusive of rain and subsoil water. Taking it at 80 
* The Rugby sewage contained, according to the author’s analyses, 27 parts of phosphoric 
acid and 42 parts of potassa, for 100 of nitrogen. 
VOL. VIII. E 
