352 
Sewage Disposal and Rivers Pollution. 
suitable it did its work as effectively and with far less nuisance than the 
ordinary sewage farm. The whole surface of the river Thames, from 
Barking to the Nore, was about equal to the smallest sewage farm proposed 
for London. 
Granting that rivers do purify sewage, as indeed must be the case 
on even a superficial view of the question, it is still, to our mind, a 
grave mistake to compare the purifying power of a river area with 
that of an equal area of land, as is here done. If the nitrifying 
power is to be taken as a criterion, the writer can say from his own 
experiments that the difference between the nitrifying power of sur- 
face soil and that of river water is so great that it is hard to compare 
them at all ; and the reason is obvious, the nitrifying organisms being 
immensely more abundant on the soil particles, all freely aerated, 
than in the body of the water, aerated to an extremely limited 
extent. Beside this the nitrifying organisms at any race form a 
layer which has a great habit of sticking fast to surfaces. 
We have dealt with sewage treatment at such a length that we 
have little space left to touch upon the kindred question of rivers 
pollution except in so far as it is implied in what has been already 
said. With the advances above described in securing clean effluents, 
and the prospect of further advances as efficient filtration is put into 
practice, there is not the difficulty there formerly was in setting up 
a standard of purity which may stand some chance of becoming an 
actuality when rivers are merely subject to ordinary polluting 
agencies. Rivers so unfortunately situated as the Irwell ought of 
course to be judged by a different standard. The standards recom- 
mended some years ago by the Rivers Pollution Commissioners have 
been a dead letter, because absurdly stringent and absurdly inelastic. 
What seems to be a suggestion in the right direction arising from 
the discussion under review is that suitable standards should be 
established for each river by local bodies empowered to do so. Mr. 
Grantham suggests that committees of the County Councils should 
conduct experiments to establish such standards for streams within 
their boundaries, and should systematically examine all effluents. 
Mr. Willis Bund replies to this that two or more County Councils 
concerned with one river might set up different standards, and 
moreover the Councils themselves are in some cases responsible for 
pollution. He thinks that a Conservancy Board for each river basin 
is necessary, though these might possibly be constituted by joint 
committees of the County Councils concerned. 
Riverside, Churchfields, Salisbury. 
J. M. H. Munro. 
THE TEWFIKIEH COLLEGE OF AGRICULTURE, 
EGYPT. 
It may be of interest to record what has been lately done by 
England to promote the agircultural prosperity of Egypt, and to 
spread the knowledge of practical and scientific agriculture in a 
