Moreover, it is suggested that in laying down new installations, it will be possible and profitable to install a destructor upon the sewage works. In such cases it would be feasible to draw upon the waste heat from the destructor to conduct the drying and other operations demanding the application of heat. In combining the destructor with the sewage plant the question of transport of the refuse from the collecting ground to the destructor would demand very careful consideration when horse haulage is employed, but with mechanical traction the question of an extra mile or two in distance hauled is not of such moment, especially as it would be off-set by the saving of fuel which would attend the diversion of the waste heat to this useful application. In fact, in cases where new lay-outs are being contemplated it is a matter for serious reflection as to whether it would not be found profitable to centralize destructor, electric generating station and Grossmann sewage treatment plant in one centralized spot, interlocking them together, and taking full advantage of such inter-connection. The destructor would furnish the necessary steam from the combustion of cinders and other refuse which it does not pay at present to exploit, or preferably other low-grade fuel to drive the electric plant, the waste steam being carried to the sewage works for the drying and other machines together with the desired proportion of live steam, while the electric station would furnish the requisite power for operating the automatic mechanical appliances. The grease recovered from the sewage, which is of a domestic character, is essentially that from soap, cooking and washing operations. It is totally free from all objectionable smell. It can be purified very easily and is of distinct value. In its crude condition the fat contains about 70 per cent. of stearic acid. During the past few years the dry powdered residue has not only been utilized in a direct form, but has also been exploited in the production of compounded fertilizers. Mixed with phosphates, sulphate of ammonia, and other nitrogenous products it has yielded a manure which has given most excellent results in farming. Considerable improvements with regard to greater efficiency and cheaper production have been made in the manufacture of compounded fertilizers from this residue, and there is every indication that still greater developments are possible in this direction.