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34 carefully to permit the escape of gases formed during the casting of the metal.

Inside cylinders were formerly cast separately and afterwards planed and bolted together to form a pair. Modern practice is to cast both inside cylinders in one piece. This requires more expensive patterns, but saves a lot of machine work.

Brass Foundry All the brass and gun metal castings are made in the brass foundry. These are much smaller pieces than iron castings and consist of axlebox brasses, injectors, cocks and taps, slide valves, and a host of miscellaneous details required in a locomotive. Much of the work is “plate moulding.” Various mixtures of metal are used from gun metal bronzes for slide valves and axlebox “brasses” to common brass for taps, etc. The metal is melted, not in large cupolas as in the iron foundry, but in plumbago crucibles which are heated in furnaces generally placed below the floor level.