noticeable during the winters of 1907 and 1908 when the water was taken from the new intake. It will be interesting to compare the results after the preliminary filters have been operated for a long period to ascertain their normal effect on efficiency and on the increased yield. [Illustration: ~Figure 11--Filters at Albany, N. Y. Results of Operation. 1899-1909. Compiled from data in Annual Reports.~] Another fact to be drawn from the plotted Albany data is the increase in the cost of filtration, both in capital charges and in operation. From 1899 until 1906 the cost of operation, including the cost of low-lift pumping, was approximately $5 per million gallons of water filtered; and the total cost of filtration, including capital charges, was about $10 per million gallons. During the year ending September 30th, 1909, the cost of operation had increased to $7.63 per million gallons, and the total cost of filtration to $15.92 per million gallons, or approximately 50% in three years. ~Table 27--Results of Bacteriological Analyses of Samples of Water at Peekskill, N. Y., Before and After Filtration.~ ~Bacteria per cubic centimeter.~ ==============+=======+=======+========+========+========+========+======== | Raw | Clear |Effluent|Effluent|Effluent|Effluent| Tap in Date. | water.| reser-| No. 1. | No. 2. | No. 3. | No. 4. | city. | | voir.| | | | | --------------+-------+-------+--------+--------+--------+--------+-------- 1909. --------------+-------+-------+--------+--------+--------+--------+-------- December 29th | 190 | 100 | ... | ... | ... | ... | ... --------------+-------+-------+--------+--------+--------+--------+-------- 1910. --------------+-------+-------+--------+--------+--------+--------+-------- February 15th | 135 | 10 | 10 | 30 | 20 | ... | 265 March 31st | 225 | 50 | 25 | 45 | 60 | ... | 35 May 18th | 300 | 29 | 22 | 26 | 35 | 43 | 36 July 6th | 300 | 44 | 9 | 3 | 41 | 10 | 31 August 16th | 60 | 5 | 0 | 4 | 1 | 13 | 15 October 3d | 550 | 14 | 12 | 14 | 38 | ... | ... November 21st | 315 | 22 | 26 | 17 | 6 | ... | ... --------------+-------+-------+--------+--------+--------+--------+-------- 1911. --------------+-------+-------+--------+--------+--------+--------+-------- January 25th | 415 | 7 | 8 | 4 | 6 | ... | 7 --------------+-------+-------+--------+--------+--------+--------+-------- Average | 277 | 30 | 14 | 16 | 26 | 22 | 65 ==============+=======+=======+========+========+========+========+========