WATER SUPPLY OF LONDON. 
237 
a system of traffic in dead meat instead of living animals. 
The idea is of course chimerical, but rapid development of 
ideas is a characteristic of the present age, and there are 
people now living who have seen greater changes actually 
effected. 
WATER SUPPLY OE LONDON. 
Dr. Letheby in his report says, the chemical composi- 
tion of the metropolitan water has not fluctuated to any 
considerable extent ; for that derived from the Thames and 
the Lea has contained from 21 to 23 grains of solid matter 
per imperial gallon during the winter months, when the rain- 
fall is the greatest, and from 17 to 17*3 grains per gallon in 
the summer, when it is least, the average for the whole year 
being about 19*3 grains per gallon, of which about 14*2 grains 
are calcareous salts, giving that degree of hardness to the 
water, the hardness being reduced to about 3’8 degrees by 
boiling the water for a quarter of an hour. The proportion 
of common salt in the water does not exceed 1*8 grains per 
gallon, and the organic matter, as estimated by the oxygen 
required to oxidise it, is not above two thirds of a grain per 
gallon. The nitrogenous matter also is remarkably small, 
ammonia being in the proportion of only one part to about 
35,000,000 parts of water, and the nitrogen, as nitrates, &c., 
as one to 630,000 parts. The water supplied to the public 
is for the most part clear and colourless ; on one occasion, 
however, during the year, it w as slightly turbid in the case of 
the Grand Junction water; on two occasions with the South- 
wark and Vauxhall water; on four with the Lambeth; and 
on six w 7 ith the Chelsea. The daily supply of water to the 
metropolis has ranged from 91,378,341 gallons per day, in 
the month of January last, to 110,094,038 gallons in the 
month of July, the average for the whole year being rather 
more than 99 millions of gallons per day, or 31*2 gallons per 
head of the population. The daily supply to Paris averaged 
24*6 gallons per head of the population ; but this includes 
the water supplied to the public fountains, &c. The number 
of houses supplied daily by the w ater companies of London is 
about 463,000. Rather more than half of the water is ob- 
tained from the River Thames at Hampton, and the rest is 
from the Lea, and from springs and wells in the chalk. The 
filtering of the w’ater is generally very effective. I have 
remarked that, except in special cases, water of moderate 
hardness, like that supplied to the metropolis, to Paris, and 
xliii. 17 
