First.-Theactive agent, hydrated ferrous oxide, is prepared within the sewage itself as a flocculent precipitate.

Second.-Hydratedferrous oxide is a deodorizer.

An almandine in which the ferrous oxide is replaced partly by magnesia is found at Luisenfeld in German East Africa.

With my knowledge of Bronze Age graves, or the importance of ferrous oxides for the colour of Greek ceramics, I'm a match for almost anybody.