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“There are dangerous qualities of water supply with regard to which, so far as I know, chemists are totally unable to measure, even to demonstrate the fatal influences that a water may have. A water may be, for instance, capable of spreading the cholera, but chemists be unable to identify the particular contamination which produces that effect. It is, I think, a matter of absolute demonstration that, in the old epidemics, when the south side of London suffered so dreadfully from cholera, the great cause of the immense mortality there was a badness of the water supply then distributed in those districts of London.”

Prof. Frankland says:

“That we have no reason to believe that the injurious character of either sewage or of the gases from a drain depends fundamentally upon the quality of that sewage or of that gas. In all probability it far more depends upon the quality of the sewage, namely, what it consists of. Now, what is the nature of the poisonous matter in the atmosphere or in the sewage? We do not know that, at all; therefore you can not possibly say when that poisonous matter is got rid of from the water or from the air. Chemical analysis can not do it, for its limit is by the power of weighing and measuring. It is not sufficiently advanced, and is one of the poorest things possible to reach those delicate points.”