=============+===========+==============+==========+========= | Parking | | | Month. | (care of | Experimental | Main | Total. | grounds), | filters. | Office. | -------------+-----------+--------------+----------+--------- 1909. -------------+-----------+--------------+----------+--------- Jul | $0.31 | ... | $0.15 | $2.63 August | 0.78 | ... | 0.15 | 2.92 September | 0.52 | ... | 0.20 | 3.42 October | 0.80 | ... | 0.10 | 3.33 November | 0.72 | ... | 0.20 | 3.98 December | 0.41 | ... | 0.17 | 2.69 -------------+-----------+--------------+----------+--------- 1910. -------------+-----------+--------------+----------+--------- January | 0.15 | ... | 0.10 | 3.02 February | 0.12 | ... | 0.17 | 4.52 March | 0.18 | ... | 0.13 | 2.96 April | 0.65 | ... | 0.15 | 4.58 May | 0.66 | ... | 0.20 | 3.63 June | 0.84 | ... | 0.16 | 7.86 -------------+-----------+--------------+----------+--------- Average. | 0.58 | ... | 0.16 | 3.80 -------------+-----------+--------------+----------+--------- Fiscal years: -------------+-----------+--------------+----------+--------- 1905-1906 | 0.01 | ... | 0.09 | 2.14 1906-1907 | 0.09 | $0.03 | 0.04 | 3.07 1907-1908 | 0.21 | 0.09 | 0.10 | 3.13 1908-1909 | 0.40 | 0.01 | 0.15 | 3.66 =============+===========+==============+==========+========= The two preliminary filters were operated at a rate of about 50,000,000 gal. per acre per day, and the three slow sand filters at rates of from 3,000,000 to 4,000,000 gal. per day. This plant was put in service during the early part of February, 1907, and was kept in practically continuous operation until the end of July, 1908. [Illustration: ~Figure 6--Washington Aqueduct, D. C., Experimental Filters Below Dalecarlia Reservoir Coagulating Basins and Apparatus.~]