i′′, are the boiler and the furnace of the engine.
k′, workshop for preparing the loam and other materials of moulding.
l, is the apartment for the patterns.
The pig-iron, coals, &c. are placed either under sheds or in the open air, round the above buildings; where are also a smith’s forge, a carpenter’s shop, and an apartment mounted with vices for chipping and rough cleaning the castings by chisels and files.
Such a foundry may be erected upon a square surface of about 80 yards in each side, and will be capable, by casting in the afternoon and evening of each day, partly in large and partly in small pieces, of turning out from 700 to 800 tons per annum, with an establishment of 100 operatives, including some moulding boys.
Of making the Moulds.—1. Each mould ought to present the exact form of its object.
2. It should have such solidity that the melted metal may be poured into it, and fill it entirely without altering its shape in any point.
3. The air which occupies the vacant spaces in it, as well as the carburetted gases generated by the heat, must have a ready vent; for if they are but partially confined, they expand by the heat, and may crack, even blow up the moulds, or at any rate become dispersed through the metal, making it vesicular and unsound.
There are three distinct methods of making the moulds:—
1. In green sand; 2. In baked sand; 3. In loam.