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They consider reasonably safe water, when it is derived from deep wells, (say 100 feet,) or from deep-seated springs, although it contains previous animal sewage, but does not exceed 10,000 parts in 100,000 parts of water. Suspicious or doubtful water is, first, river or flowing water which exhibits any proportion, however small, of previous sewage; and, second, well or spring water containing 10,000 to 20,000 parts. Dangerous water is, first, river or flowing water which exhibits more than 20,000 parts of previous animal contamination; second, river or flow water containing less than 20,000 parts of previous contamination, coming from sewage discharged into it directly, or mingling with it as surface drainage; third, well or deep-seated springs containing more than 20,000 parts, because previous contamination is in direct proportion to the amount of such contamination.

The value of an analysis, sanitarily considered, is questioned. Mr. Simon, medical officer of Her Majesty’s Privy Council, testified, before the Royal Commission on Water Supply, on this point, as follows: