SANITARY NOTES ON POTABLE WATER. 
565 
solution. This was in all other experiments not the case. 
The object of this modification was to further confirm a result 
which I had obtained before, that the physiological action of 
spongy iron in preventing putrefaction is not dependent on 
the absence of oxygen. 
After continuing the passage of New River water through 
through these filters at the ordinary rate for a fortnight, for 
the sake of thoroughly washing the materials, the filters 
were connected each with a glass flask containing some fresh 
uncooked meat, and generally arranged as before. 
The filtration of water was then continued for three more 
weeks, at the ordinary regulated speed, when the several 
samples of meat were taken out of the flasks. After being 
placed on similar dishes, I had them successively handed to 
me, blindfolded, for examination of their smell, so as to pre¬ 
vent any preconception on my part. It must be borne in 
mind that fresh meat in itself has more smell than cooked 
meat, therefore any slight putrefaction cannot be as readily 
distinguished in the former as in the latter. 
The following was the result of my examination :—The 
samples which had been in connection with the two spongy 
iron filters exhibited a peculiar slight smell, reminding me 
of cheese, w'hich, however, was totally different from the 
smell of putrid meat. The sample which had been in 
contact with the water filtered through animal charcoal 
was offensive, having a decidedly putrid smell. At the 
same time, when the preceding experiments were com¬ 
menced, I immersed tw T o other glass flasks which contained 
some fresh meat for an hour ancl a half into boiling water. 
One of these flasks was then connected with the spongy 
iron filter which yielded w 7 ater containing oxygen in solution, 
with a view of comparing the action of that filter with former 
experiments when there was no oxygen in the filtered water. 
Into the other flask, which contained boiled meat, I passed, 
without opening the stopper, a small quantity of unfiltered 
New River water, when at once the inlet and outlet 
tube were closed air-tight. The object of this latter 
experiment was further to test directly whether the com¬ 
paratively low temperature then prevailing had any sensible 
influence on the result of the experiments in rendering 
bacteria inactive. This w 7 as again decidedly negatived, 
for that small quantity of unfiltered New River water sufficed 
to render the meat, after three w T eeks^ standing, very offen¬ 
sive and putrid * whilst the corresponding sample, which 
also coffiained boiled meat, and had been connected with 
one of the spongy iron filters, exhibited only the smell of 
