On Living Organisms 
[March, 
III. ON LIVING ORGANISMS WITH REFERENCE 
TO POLLUTED WATERS. 
By J. W. Slater. 
T is well known that the late Royal Rivers’ Pollution 
(sj) Commission, in consequence of their observations and 
experiments, concluded that a river if once polluted 
with foecal matter does not become purified by any natural 
process, at least within the length of any stream in the 
United Kingdom. Dr. Meymott Tidy, from a paper which 
he has recently communicated to the Chemical Society, 
holds, on the contrary, the opinion that rivers after contami- 
nation with animal or vegetable matter — excrementitious 
substances being necessarily included — are capable of self- 
purification, through the instrumentality of subsidence, of 
the absorption of oxygen, which is the more rapid the more 
impetuous the current, or by the agency of fish. It can 
scarcely, I think, be contended that fish can have any power 
of freeing water from dissolved impurities. 
Some years ago an eminent French chemist came to con- 
clusions very similar to those which have been made known 
by Dr. Tidy. He had proposed to estimate the relative 
purity of waters by the amount of free oxygen which they 
hold in solution and which he determined volumetrically by 
means of a standard solution of the “ hydrosulphite” of 
Schiitzenberger and De Lalande. Among other waters 
which he thus examined were those of the river Vesle, above 
and below Rheims. As this town is the seat of very exten- 
sive woollen manufactures, the Vesle is polluted in a very 
similar manner to the Aire at Leeds, with both organic and 
inorganic refuse of the most varied kinds. He found that 
the water at the distance of some miles above the town con- 
tained a normal proportion of free oxygen. Approaching 
to Rheims and receiving the waste liquids of manufactories, 
it showed a smaller and smaller percentage, and a minimum 
was reached a little below the town. Afterwards, as the 
stream continued its course through an open agricultural 
district, the proportion of oxygen again increased, and at the 
distance of about twenty miles below Rheims' — I quote from 
memory — it showed the same percentage as had been 
obtained above the city. At the same time he observed a 
series of changes in the organic forms inhabiting the river, 
which in his opinion proceeded step for step with the de- 
