But when we come to the treatment of this material we fail miserably. At the central station the solid matter, in reality a mud or sludge, is separated from the free liquid. The disposal of the latter offers little or no difficulty. It can be rendered innocuous, and is therefore permitted to resume its part in the scheme of Nature. But the sludge: that is a different proposition. A few figures concerning the situation in regard to London may prove illuminating. Certainly they will serve to demonstrate the magnitude of the volume of this waste. During the year over 100,000,000,000 million gallons of sewage are received from approximately 5,350,000 people occupying 95,000 acres. Each million gallons of sewage yields about 25 tons of sludge. The total quantity of solid matter is approximately 200,000 tons. It costs about 30s.--$7.50--to treat and dispose of each million gallons of raw sewage. The total yield of sludge exceeds 2,600,000 tons a year. It is an incubus having no ostensible commercial value, so is transferred to vessels to be carried out to sea where it is thrown overboard. Seeing that it costs about £17 13s.--$88--to run each vessel out and back again, and that some 111,000 journeys are made during the year, dumping the sludge costs the ratepayers of London nearly £2,000,000--$10,000,000--a year. The crime incidental to London is repeated throughout the country, and in this way, as Sir William Crookes pointed out, the nation is deliberately discarding 16,000,000 tons of valuable nitrogenous material which, were it subject to proper treatment, might be reclaimed to participate in the nourishment of our broad acres. Estimating the value of this potential fertilizing agent at the modest figure of one ¹⁄₂d.--1 cent--per pound we are, of malice aforethought, throwing away a round £35,000,000--$175,000,000--per annum. But this is not the most disturbing feature. For the most part the sludge, and in the case of seaside towns the crude sewage, is discharged upon potential valuable fishing grounds, to the destruction or infection of the fish, especially shell-fish. Furthermore, one must not imagine because the objectionable and dangerous refuse is abandoned well out to sea its serious dangers are removed. Tides and currents play strange tricks, the result being that much of this filth is thrown back upon the coasts, perhaps at a distant point, to wreak possible havoc.