Columns: A - Period of sedimentation in days. B - Turbidity in parts per million. C - Bacteria per cubic centimeter. ============+=====+=====+=======+===================== | | | |~Percentage Removed~ Reservoirs.| A | B | C |----------+---------- | | | | Turbidity| Bacteria ------------+-----+-----+-------+----------+---------- River | ... | 106 | 6,400 | ... | ... Dalecarlia | 2.2 | 50 | 5,000 | 53 | 22 Georgetown | 2.2 | 38 | 3,400 | 24 | 32 McMillan | 2.8 | 26 | 2,000 | 31 | 41 ------------+-----+-----+-------+----------+---------- Totals and | | | | | averages | 7.2 | ... | ... | 75 | 69 ============+=====+=====+=======+==========+========== While it may perhaps seem unreasonable to single out Washington as a particular sufferer in this respect, it is highly probable that a large share of the typhoid is still caused by secondary infection, flies, impure milk, and private and public wells. The speaker remembers distinctly that ten years ago, when he made an investigation into the purity of the water of about 100 public wells in that city, a large number of them showed unmistakable evidence of being polluted with sewagic matter. Conclusive evidence would be secured to dispel any doubt as to the sanitary quality of the filtered product if hypochlorite of lime were added to the filtered water throughout one year or throughout the typhoid months. It seems strange to the speaker, that for this, if for no other reason, this safe and non-injurious germicide has not as yet been used at Washington, in view of the fact that at the present time it is being used continuously or intermittently in the treatment of the water supplies of scores of the most important cities of this country, among which may be mentioned New York, Philadelphia, Cincinnati, Pittsburg, St. Louis, and Minneapolis.