BOOK VII.

227

hearth, for it does not project beyond the wall. The hide of the bellows isfixed to the bellows-boards with its own peculiar kind of iron nails. It joinsboth bellows-boards to the head, and over it there are cross strips ofhide fixed to the bellows-boards with broad-headed nails, and similarlyfixed to the head. The middle board of the bellows rests on an iron bar,to which it is fastened with iron nails clinched on both ends, so that it cannotmove ; the iron bar is fixed between two upright posts, through which itpenetrates. Higher up on these upright posts there is a wooden axle, withiron journals which revolve in the holes in the posts. In the middle ofthis axle there is mortised a lever, fixed with iron nails to prevent it fromflying out; the lever is five and a half feet long, and its posterior end isengaged in the iron ring of an iron rod which reaches to the “ tail ” of thelowest bellows-board, and there engages another similar ring. And so whenthe workman pulls down the lever, the lower part of the bellows is raised anddrives the wind into the nozzle ; then the wind, penetrating through the holein the middle bellows-board, which is called the air-hole, lifts up the upperpart of the bellows, upon whose upper board is a piece of lead, heavy enoughto press down that part of the bellows again, and this being pressed downblows a blast through the nozzle. This is the principle of the double bellows,which is peculiar to the iron hoop where are placed the triangular crucibles inwhich copper ore is smelted and copper is melted.

A —Iron hoop. B —Double bellows. C —Its nozzle. D —Lever.

zrwitm i') ;

I have spoken of the furnaces and the iron hoop ; I will now speak ofthe muffles and the crucibles. The muffle is made of clay, in the shapeof an inverted gutter tile ; it covers the scorifiers, lest coal dust fall intothem and interfere with the assay. It is a palm and a half broad, and theheight, which corresponds with the mouth of the furnace, is generally a palm,