a machine so contrived as to inspire and expire the air by turns, by enlarging and contracting its capacity. This machine is used in chambers and kitchens, in forges, furnaces, and founderies, to fan or blow up the fire; and it serves also for organs and other pneumatic instruments, to give them a proper degree of air. It is of various construction, according to the different purposes to which it is applied; but in general it is 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, and also on the hoops which separate the boards, that the leather may easily open and fold again; and a tube of iron, brass, or copper, is fastened to the undermost board, while there is a valve within, which covers the holes in the under board to keep in the air.

Anacharsis the Scythian is reputed the inventor of bellows. The action of bellows bears a near affinity to that of the lungs; and what we call blowing in the former, affords a good illustration of what is called respiring in the latter. Even animal life itself may on some occasions be supported by blowing into the lungs with a pair of bellows. This is shown by Dr Hooke's well-known experiment. Having laid the thorax of a dog bare, by cutting away the ribs and diaphragm, pericardium, &c., and having cut off the aspera arteria below the epiglottis, and bound it on the nose of a bellows, this ingenious person found, that as he blewed the dog recovered, and as he ceased it fell into convulsions; and thus the animal was kept alternately alive and dead for more than an hour.

Smiths' and founders' bellows, whether single or double, are wrought by means of a rocker, with a string or chain fastened to it, which the workman pulls. The bellows pipe is fitted into that of the tewel. One of the boards is fixed so as not to play at all. By drawing down the handle of the rocker, the movable board rises; and, by means of a weight on the top of the upper board, it sinks again. The bellows of forges and furnaces of mines usually receive their motion from the wheels of a water-mill or steam-engine. Others, as the bellows of enamellers, are wrought by means of one or more steps or treddles under the workman's feet. Lastly, the bellows of organs are wrought by a man called the blower; and in small organs by the hand or foot of the player. See Blowing Machinery.

Hessian Bellows is a contrivance for driving air into a mine to facilitate the respiration of the miners.