This Misfortune happened at Birmingham, and other Places.
432. The Desideratum is, quickly to apply, and remove the Borings, keeping the Machine nearly Air-tight. For, it is now well known, that the Gass will explode, if one-third Part of common Air be introduced: or, if less; it may unite with the Gass, and detract from its Levity.
433. The following Particulars may likewise be considered as an Improvement.
II.
1. To lay a Plate of Iron, Brass, or Copper, over the Hearth; which, if made of cast Iron, will be apt to crack, in Contact with the Steam; and will also unite with and concrete the Iron Turnings or Gun-Borings into a solid Mass, that woud be separated with Difficulty.
2. To make the Dross-Pit in the Form of a hollow Wedge, narrow at the Top: screwing and luting it to the South Side of the Hearth. It shoud hold the Dross arising from a Ton of Borings; which will be sufficient for the Inflation of a Balloon, to carry one Person.
3. On the North Side is to be erected a Platform of Brick, a Yard square, floored with a Plate of Iron: the inside Surface to be even with the Bottom of the Hearth.
4. The Ton of Borings is to be placed on the Floor, and covered with another Muffle, secured and luted to the Side of the Hearth: having a Communication of two Inches high, and one Yard wide, with the Bottom of the Hearth: as the Dross-Pit has.
5. A Brass or Copper Rake is to remain within the two Muffles: to press forward the Borings, spread them over the Hearth; stir them frequently;—by turning the Instrument, scrape them into the Dross-Pit; and apply fresh from the Deposit.
6. To perform these manual Operations within the Machine kept Air-tight; it will be necessary, at the exterior End of the Muffle, to fasten a strong leathern Case, made very wide and pliant, and two Yards long: into which the End of the Rake-Handle is to be inserted.