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4 capital outlay, which could not profitably be expended by a small works. It pays to make the necessary special time and labour-saving tools and appliances only when several similar engines are built together, or, as in many railway works, when much of the “motion work” and other parts of one class of engine are interchangeable with those of another class. Naturally when the conditions are such that a large number of similar engines can be constructed together with the help of special tools and “jigs,” the cost per locomotive is very considerably reduced. An isolated engine of a new design is necessarily expensive, but it generally pays a railway company to build such an engine, so that it can be tested thoroughly, and the necessary modifications and alterations made before placing a large order.

Progress of Work through the Workshops. A general idea of the order in which work passes through the various shops may be gained from Fig. 1, beginning with the raw materials. The latter term may and generally does include a considerable quantity of semi-finished material. Steel castings, axles, and tyres may be mentioned specially in this connection. One or two locomotive works, both of the railway companies and private firms, make their own steel castings, but generally these are purchased from outside manufacturers. The same applies to rough forged axles. Tyres are, in most cases, rolled at the