BELLOW, a machine so contrived as to expire and inspire the air by turns, by enlarging and contracting its capacity.
This machine is used in chambers and kitchens, in forges, furnaces, and foundries, to blow up the fire: It serves also for organs and other pneumatic instruments.
ments, to give them a proper degree of air: All these are of various constructions, according to their different purposes; but in general they are composed of two flat boards, sometimes of an oval, sometimes of a triangular figure: Two or more hoops, bent according to the figure of the boards, are placed between them; a piece of leather, broad in the middle, and narrow at both ends, is nailed on the edges of the boards, which it thus unites together; as also on the hoops which separate the boards, that the leather may the easier open and fold again; a tube of iron, brass, or copper is fastened to the undermost board, and there is a valve within that covers the holes in the under-board to keep in the air.
Each pair of bellows imported is valued in the book of rates at three shillings and four pence, and pays duty 710/100 d. whereof 625/100 d. is drawn back on exportation. See PNEUMATICS.