a machine so contrived as to expiro 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, to give them a proper degree of air. All these are of various contrivances, 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, brafs, 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.

Anacharis the Scythian is recorded as 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 respiration in the latter. Animal life itself may on some occasions be subsisted by blowing into the lungs with a pair of bellows. Dr Hooke's experiment to this effect is famous: 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, he found, that as he blewed, the dog recovered, and as he ceased, fell convulsive; and thus was the animal kept alternately alive and dead above the space of an hour. There are bellows made wholly of wood, without any leather about them; one of which is preserved in the repository of the Royal Society; and Dr Plot describes another in the copper-works at Elafton in Staffordshire. Aut. della Fruta contrived a substitute for bellows, to spare the expence thereof in the fusion of metals. This is called by Kircher camera acuta, and in England commonly the water bellows; where water falling through a funnel into a close vessel, sends from it so much air continually as blows the fire. See the article FURNACE, where different blowing machines of this kind are described.

Smiths and founders bellows, whether single or double, are wrought by means of a rocker, with a string or chain fastened thereto, which the workman pulls. The bellows pipe is fitted into that of the tevel. One of the boards is fixed, so as not to play at all. By drawing down the handle of the rocker, the moveable board rises, and by means of a weight on the top of the upper board, sinks again. The bellows of forges and furnaces of mines usually receive their motion from the wheels of a water-mill. 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 foot of the player. Butchers have also a kind of blast or bellows of a peculiar make, by which they bloat or blow up their meat when killed, in order to piecing or parting it the better.

Bone BELLOWS, θυραίνεις οστεοι, occur in Herodotus for those applied by the Scythians to the genitals of mares, in order to distend the uterus, and by this compression make them yield a greater quantity of milk.

Hessian BELLOWS are a contrivance for driving air into a mine for the respiration of the miners. This M. Papin improved, changing its cylindrical form into a spiral one; and with this, working it only with his foot, he could make wind to raise a two pound weight.

Hydrostatic BELLOWS. See HYDROSTATICS.