562 
SANITARY NOTES ON POTABLE WATER. 
periments upon the separation of fermenting matter from 
water by filtration. I will now explain some further experi¬ 
ments which I made since reading those papers to the Royal 
Society, to which I have alluded above. 
The purifying media experimented upon were, as formerly, 
animal charcoal and spongy iron. All former experiments 
were based on the supposition that the meat, when being 
exposed to the action of filtered water, must necessarily, in 
the first instance, be disinfected by boiling. I proved in 
this way that water, after passing through animal charcoal, 
does not prevent putrefaction of the meat. The same water, 
and even hay infusion, after filtration through spongy iron, 
under otherwise like conditions, is incapable of inducing, for 
many months at any rate, putrefaction of the meat, if brought 
in contact with it under conditions which I have specified. 
However, on consideration of those results, it appeared 
probable that water, after passing through spongy iron, might 
have itself antiseptic properties sufficiently strong so as not 
only to be unable to support the existence of putrescent 
processes in the water itself, but even to prevent without 
preliminary boiling the putrefaction of meat. 
To test this, similar vessels were employed to those de¬ 
scribed in the first paper before referred to. They were not, 
however, for reasons which will presently be seen provided 
with a perforated bottom, but some fresh meat which had 
not been boiled was placed on the bottom of the vessel and 
covered by a cup with perforated sides and a neck at the top. 
From the neck a tube was passed through and made tight in 
a neck at the base of the filtering vessel, being connected 
there with a stopcock for regulating the flow of water. The 
vessel was next filled five to six inches high with ordinary 
spongy iron, and continuously supplied with New River 
water, which at the time was in an unusually bad condition, 
owing to floods. 
The meat was, therefore, not in contact with the spongy 
iron, but solely with the water which had passed through 
that material. In this manner the apparatus was as far as 
possible kept going constantly for three weeks, a volume of 
water equal to the bulk of spongy iron passing through it in 
about fortv-five minutes. The meat was at the end of that 
time in a perfectly fresh condition. To about half an inch 
from the exterior it was white, but the interior was still red. 
A subsequent repetition gave a like result. 
The experiment was at the same time modified in such a 
way that the filter, otherwise arranged as before, was merely 
kept full of water, any filtration through it being dispensed 
