The floor of the forge shop is a still more simple matter than that of the foundry. The ground is prepared as before, and leveled off a foot below where the top of the floor is to be. This space is filled in with clean gravel mixed with clay, in the proportion of three parts of the former to one of the latter, laid down wet and thoroughly rammed down with a broad-faced rammer.

Sharp sand, or the fine cinders from forges, are sifted over this to prevent the surface from becoming muddy when accidentally wet. In the case of a forge shop, concrete is hardly advisable, being liable to be broken up by the heavy shocks from hammers and the rough usage to which it would be subjected.

Of course it might be made thick enough to endure these conditions, but would be quite expensive and would answer the purpose no better than a hard-rammed floor of earth, as above described.

For the floor of the boiler room, flag-stones or hard-burned bricks may be used, whichever is found most convenient. If stones are used they should be cut to a certain width, in one direction at least, in order that they may be laid in courses so as to "break joints," as shown in Fig. 42. They should be from 1« to 2« inches thick.

Supposing the ground to be sufficiently solid for the purpose, it is prepared by leveling, the same as heretofore described, and at least 4 inches plus the thickness of the stones below where the top of the floor is to be. Sharp sand should be filled in 4 inches deep, and the stones laid upon this, the sand being rammed closely under each course as laid.

When completed, dry sand to the depth of « inch is spread over the whole and swept back and forth to force as much as possible down through the joints. This is the cheaper and, more simple method.

If it is desired to make a more substantial pavement, the earth should be leveled off at such a height that only an inch space is left between it and the stones, and an inch course of a mixture of one part Portland cement and two parts of sharp sand worked up rather soft.

The stones are laid on this while it is wet, and all spaces filled as each course is laid and leveled. Some masons may prefer to make this mixture with a portion of lime added, the same as in cement mortar.

Should bricks be used they may be laid on either the sand or cement bed the same as described for stone, except that about half the depth of sand will be sufficient. They should be arranged in the form shown in Fig. 43, by which method they are firmly bound together, and, if laid only upon sand, will retain their places for a long time. They are in some respects to be preferred to stone.

Where the ground is soft or has soft spots, it will be necessary to excavate to comparatively hard ground and then fill in with solid earth - preferably gravel - which is to be tightly rammed or puddled to make it firm. Upon this the layer of sand may be placed as described.

It is sometimes desirable to have engine room floors paved also, and occasionally with much larger and heavier stones than those described above. They should be carefully laid in cement mortar on a good concrete bed.

If rolled iron plates, or cast iron plates are to be used they should be supported by brick piers and iron bars, or by brick walls supporting their ends, and at other points if their dimensions render it necessary.

Cast iron plates may be made with strengthening ribs on their under side, by which means the supports may be much farther apart. Plates of rolled sheet steel with raised figures of various forms and patterns can be had, which make an excellent floor for engine or boiler rooms.

The modern engine room is a much better appointed department than formerly. It should have a floor of narrow, matched hard pine, smoothly leveled off by hand planing, and the surface kept oiled with boiled linseed oil.

The floor of the storehouse is of 2-inch planks, laid on 3 × 12 inch joists placed 15 inches from center to center, which in turn are supported by timbers 10 × 12 inches, placed 10 feet apart from center to center and resting on piers, leaving 15 feet between supports.

It the load which this floor is to carry warrants it, this distance should be reduced to 10 feet. The floor planks may be matched if desired, but for a floor for heavy machinery storage they need not be either matched or planed.

The carpenter shop floor is of similar construction to the above, except that the joists are 2 × 10 inches, laid 18 inches from center to center, and supported at distances of 13 feet by 8 × 10 inch timbers, resting on piers 10 feet apart.