ON THE PURIFICATION OF DRINKING WATER. 249 
By those who advocate the superiority of a continuous 
over an intermittent supply of water, the inconveniences and 
expense of cisternage have been forcibly pointed out ; and 
it has been argued that by the adoption of a constant supply, 
the necessity of reservoirs in private houses, would be got rid 
of. This, however, is a fallacy. Cisterns or other reservoirs 
would still be required, on account of the inevitable interrup- 
tions of supply arising from repairs to the mains and service 
pipes, alterations, extensions, and other causes. At the 
present time these are sufficiently numerous and annoying ;f 
but they would in all probability be considerably augmented 
if the mains and service pipes were kept constantly charged ; 
as the bursting of pipes from frosts would then be of more 
frequent occurrence ; and the slightest repair to a service 
pipe would require the interruption of the supply to a street, 
or, perchance, to a district. 
Moreover, in the cases of those companies which do not 
filter the water they supply, house cisterns are absolutely 
required as deposit vessels, as the water furnished is occasion- 
ally turbid and muddy, and quite unfit for immediate use. 
This statement applies to the New River Water, which is 
one of the best of the unfiltered Metropolitan waters. Al- 
though it is conveyed many miles by an acqueduct, which to 
a certain extent may be regarded as a deposit reservoir, and 
is afterwards allowed to deposit in the proper reservoirs at 
the company's works, yet at certain seasons, as after heavy 
rains, the water supplied by the company is very turbid, and 
does not recover its limpidity after two or three days' reten- 
tion in the house cistern. 
2. Filtration. — This process has for its chief object the 
t The total number of interruptions which occurred in the year 
ending September 30, 1849, to the tenants of the Grand Junction 
Water Company was 2316, being an average of 6. 34 per day, Sundays 
included. The average time during which the water was shut off 
was from half-an-hour to six hours, according to the character of the 
works required. 
