Moreover, in elaborating his fruitful thoughts the investigator is compelled to bear in mind varying conditions. Accordingly he must adapt his ideas to the prevailing requirements. Obviously it would be inexpedient to concentrate perfecting effort upon one definite system. The plant involved may necessitate a capital outlay possible only to the wealthy firm or city, and utterly beyond the small man anxious to embark upon such an enterprise, or be impracticable to the average town, to which the plant, owing to the limited volume of material to be handled, would never justify the probable expense. In these circumstances we see plants and methods being adapted to varying demands so that the reclamation of the urgently required fats, oils and greases may be pursued by one and all. In a previous chapter, describing the recovery of these commodities from the swill-tubs of the army, I referred to one system which is wholly mechanical in its operation. In this instance success depends essentially upon the centrifugal turbine extractor or “whizzer,” which it must be admitted has proved exceedingly attractive in application. For this reason the “Iwel” system, as it is called, has met with conspicuous success and wide application, being found in every industry. But there is another system, or rather wide range of systems, known as the Scott, differing entirely from the one already mentioned. This, too, is of British origin and construction, and compels attention from its applicability to every possible requirement as well as adaptability to every conceivable condition, from the factory handling only a few thousand pounds of miscellaneous fat-carrying refuse a day, to the huge packing plants to be found upon the American continent, both North and South, Australia and New Zealand, where the accumulations of fresh fat are imposing, and where the necessity for prompt big-scale treatment to secure the attractive prices ruling for high-grade fats is so obvious. The operations of the firm under review demand additional attention inasmuch as, through the combined efforts of its chemists and engineers, it has been able to evolve and perfect a process which is distinctly remarkable, seeing that it enables all but 1 per cent. of the fat contained in the crude refuse to be reclaimed, and in such a manner as to render the method completely profitable.