III.
434. The Mode of Operation.
The Borings being spread on the Hearth, and red hot; the Steam Pipe is to be opened, and instantly shut. The Gass being suddenly extricated; the Pipe is to be opened, and shut again as before: the Borings pushed into the Dross-Pit, and a fresh Supply spread. This Process to be renewed, till the Inflation is completed.
If it be thought necessary to prevent the Steam from communicating with the whole Depôt of Borings, and so evolve too much Gass; a little Brass Door with Hinges of the same, might be made to hang from the Top of the Communication between the two Muffles: which Door opening inwards, and hanging vertically, woud by the Pressure of the Gass, stop up the Open: and yet, if made strong, not prevent the Operations of the Rake, at proper Times.
IIII.
435. The Machine woud be less complex, with one large Muffle, somewhat longer North and South than the Hearth; furnished with leathern Case and Rake. Put in the Borings at one End: keep the Steam-Pipe always open; with a Hand at the Rake; pushing away the Dross, and pressing forwards fresh Borings.
V.
436. Further: it has since occurred, that a Machine in the Form of a gun-barrel, extended in all its Dimensions, will probably answer every Intention.
And of this Kind are the hollow cylindrical Tubes, of different Lengths, and about a Foot in Diameter,[138] which are cast, for the Conveyance of Steam, from the Boiler of a Steam-Engine.
Such a one, (previously lined with a Cylinder of Copper, or malleable Iron, to prevent the Adhesion of the Borings, when reduced to a Calx by the Admission of Steam;) might be placed horizontally over a Stove, (with or without a Chimney) and surrounded with red hot Coals.