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Rh diameter, which there dip into the river, and through which the water is drawn by the pumps. The engines are three in number, each of 50 horse power nominal, with six boilers. They are contained in a handsome brick building designed by Mr. Christopher Wray, of Cannon Street, London. All these buildings are of similar design. The water is discharged into six settling tanks, each five hundred feet long by two hundred and fifty feet wide; they are walled and floored with brick masonry. The floors are arranged with a slope and channels to facilitate the cleansing. The water is allowed to stand quiescent for thirty-six hours, when a large quantity, amounting to eight or ten inches, of mud accumulates. This is flushed away through the sludge culvert into the river. The water after settlement is drawn off from the tanks. An arrangement is provided from which it is taken from just beneath the surface, continuously, as the surface sinks to within three feet of the bottom. This lower water is never drawn off for consumption; it is used for cleaning out the tanks. The quantity of four feet in depth of two of these tanks is required for one day’s supply of six million gallons. The water then passes through iron pipes, forty-two inches in diameter, to the filters. These are eight in number, each two hundred feet by one hundred feet in area; they contain four feet in depth of filtering media when fully charged, and two feet in depth of water. The water passes downward through the filtering media, and through brick channels beneath, into cast-iron pipes, by which it is conducted to the covered well. This is a small building over a large octagonal tank, where the water is collected from all the working filters previous to starting on its journey to Calcutta. In the covered well it passes over a marble platform, where its purity can be observed. The water flows thence through the forty-two inch main, which is capable, under the most favourable circumstances, of passing eight million of gallons through it in twenty-four hours. The purity of the water is daily tested in Calcutta by the Government analyst, Dr. Macnamara. The result proves it to be generally even purer than the water of Loch Katrine which supplies Glasgow, so effectually are the means of providing for its cleansing and filtering in the dry season. The real difficulty is during the rains; and to overcome this, the Engineer is of opinion that some alteration is necessary. The present mode of comparing purity is by the quantity of ammonia of organic matters. This usually varies from .04 to .08 of a millionth,—a quantity so small that it may be said to be practically pure.’ Having gone fully into