1884.1 
The Ghost of the Season. 
259 
French Leeds, but further down it gradually returns to the 
same condition which it had above the town. These suc- 
cessive changes, first for the worse and then for the better, 
were shown by the volume of free oxygen held in solution 
in the water, as determined by De Lalande’s process. As 
the impurities increased this free oxygen very naturally dimi- 
nished, thus proving, by the way, that such free oxygen does 
actually serve for consuming organic impurities, and that if 
these exceed a certain quantity it is all used up faster than 
it can be absorbed from the atmosphere. But as the stream 
flowed on the absorption of oxygen continued, and it gra- 
dually gained ground and was able to destroy the impurities. 
By degrees, too, water-plants and animals of higher grades, 
which were unable to exist immediately below the town, now 
appeared and completed the work of purification. 
I admit, of course, that if the quantity of pollution is too 
great m comparison to the volume of the river, — if water- 
plants and animals are poisoned by manufacturing refuse, 
and if the supply of filth is continuous all along the course 
of the river, — its waters will fail to be purified by the natural 
agents above mentioned. But this is a very different propo- 
sition from the sweeping conclusion of the Commission. 
Whether living organisms, present as an impurity in water, 
are capable of being oxidised and destroyed by aeration, by 
the aCtion of aquatic vegetation, or whether they are capable 
of being removed in any other manner, is a distinct question, 
to which I shall revert below. 
The dogma of the Commission is to some extent based 
upon the analytical method used by them, or, more strictly 
speaking, by Professor Frankland. I am not about to enter 
upon a discussion of this method, or to undervalue it in 
comparison with any other method. But as Dr. Percy 
Frankland asked his audience to condemn the ABC process 
for the purification of sewage, upon the strength of an 
analysis made by that method, I am compelled to bring for- 
ward a certain historical faCt. 
In the beginning of the year 1872 the Native Guano 
Company, proprietors of the ABC process, were beginning 
to treat the sewage of Leeds. A formal trial of forty-eight 
hours was made under the superintendence of the Sewage 
Committee of the Leeds Town Council. Every hour a 
bottle of the effluent water was taken and sealed by officials 
of the Council, and at the end of the forty-eight hours the 
contents of these bottles were poured into a large vessel, 
and thoroughly stirred up together. It is therefore evident 
that any two samples of water taken out of this vessel 
