case where chemicals in solution are added to the sewage.) Not only does
it act as a mechanical precipitant, but it possesses the property of
combining chemically with some of the soluble organic matter and
carrying it down in an insoluble form.

"Second.--Hydrated ferrous oxide is a deodorizer.

"Third.--By this process the soluble organic matter is reduced to a
condition favorable to the further and complete purification by natural
agencies.

"Fourth.--The effluent is not liable to secondary putrefaction."

Mr. Alfred E. Fletcher also investigated the process subsequently, and
reports as follows:

"The treatment causes a reduction in the oxidizable matter in the
sewage, varying from 60 to 80 per cent. The practical result of the
process is a very rapid and complete clarification of the sewage, which
enables the sludge to separate freely.

"It was noticed that while the raw sewage filters very slowly, so that
500 c.c. required 96 hours to pass through a paper filter, the
electrically treated sewage settled well and filtered rapidly.

"Samples of the raw sewage, having but little smell when fresh, stank
strongly on the third day. The treated samples, however, had no smell
originally, and remain sweet, without putrefactive change.

"In producing this result two agencies are at work, there is the action