172 
COMPOSITION AND QUALITY OF THE METKOPOLITAN WATERS IN 
JULY, 1866. 
The following are the returns of the Metropolitan Association of Medical Officers of 
Health:— 
Names of Water 
Companies. 
Total Solid 
Matter 
per Gallon. 
Loss by 
Ignition.* 
Oxidizable 
Organic 
Matter.! 
Hare 
Before 
Boiling. 
[ness. 
After 
Boiling, j 
Thames Water Compa¬ 
nies :— 
Grains. 
Grains. 
Grains. 
Degrees. 
Degrees. | 
Grand Junction. 
17-49 
0-70 
0-60 
13-0 
2-5 j 
West Middlesex . 
16-77 
0-80 
0-76 
12-5 
2-0 1 
Southwark and Yauxhall 
17-10 
0-58 
0-49 
13-0 
3-5 
Chelsea . 
16-60 
0-68 
0-60 
13-0 
2-5 
Lambeth . 
18-39 
0-75 
0-72 
13-0 
2-5 
Other Companies :— 
Kent .. 
27-86 
1-00 
0-02 
18-0 
8-5 
New River. 
17-16 
1-90 
0-20 
130 
30 
East London. 
18-16 
0-80 
0-40 
13-5 
3-5 
H. Letheby, M.B. 
The analysis of the metropolitan waters during the month of July shows that in every 
case there is less than the average proportion of saline and organic matters, and the re¬ 
duction of the latter, which is the most important constituent of potable water, is most 
marked in the waters derived from other sources than the river Thames ; for while the 
amount of organic impurity in the latter has ranged from 0’49 to 0'76 of a grain per 
gallon, that of the former had been from 0'2 to OH per gallon; indeed, the quantity of 
organic matter in the Kent water has fallen from an average of 0*2 of a grain to 0'02 ; 
that of the New River from 0-46 to 0-2 ; and that of the East London from 0-53 to OH, 
These reductions in the quantity of organic matter are chiefly due to the care with 
which the processes of filtration are conducted; and if these analytical results are com¬ 
pared with those of a few years ago the improvement is still more remarkable. It is 
very probable, however, that the most perfect processes of purification, so far as they can 
be used at the works of the water companies, will never be sufficient to ensure such a 
purity of water as the complete removal of those subtle agents of disease which even the 
most refined appliances of the chemist have failed to discover. It may, therefore, well 
be that all discoverable traces of organic matter may be removed from water, and yet it 
may still contain enough of the minute germs of disease to manifest its morbific action 
wherever it is used. Experience, indeed, teaches us tliat it is not the quantity of organic 
matter in water so much as its quality which determines its dangerous properties; and, 
if it be true, as modern pathological science has almost demonstrated, that the real agent 
cf such diseases as infectious fevers, cholera, the rinderpest, and other allied zymotic 
maladies, are living germs, and not a gas or vapour, or dead organic miasm, it must rest 
with the physiologist rather than with the chemist to decide on the means which are 
best suited for their destruction; and it is more than probable that the chemist would 
be putting forward very dangerous propositions if, by relying on his science alone, he 
ventured to dogmatize on so difficult a subject. That which has been abundantly proved 
in respect of smallpox and some other infectious diseases is very applicable to the pre- 
* The loss by ignition represents a variety of volatile matters, as well as organic matter, as 
ammoriiacal salts, moisture, and the volatile constituents of nitrates and nitrites. 
t The oxidizable organic matter is determined by a standard solution of permanganate of 
potash—the available oxygen of which is to the organic matter as 1‘8; and the results are 
controlled by the examination of the colour of the water when seen through a glass tube two 
eet ill length and two inches in diameter. 
