BOOK III.
MACHINES FOR RAISING WATER BY COMPRESSÜRE INDEPEND-ENTLY OF ATMOSPHERIC INFLUENCE.
C H A P T E R I .
Definition of machines described in this Book—Forcing Pumps—Analogy between them and bellows—History of the bellows that of the pump—Forcing pumps are water bellows—The Bellows of antedi-luvian origin—Tubal Cain—Anacharsis—Vulcan in his forge—Egyptian , Hindoo, and Peruvian blowingtubes—Primitive bellows of goldsmiths in Barbary—Similar instrumenta employed to eject liquids—De-vices to obtain a continuous blast—Double bellows of the Foulah blacksmiths, without valves—SimpleAsiatie bellows—Domestic bellows of modern Egypt —Double bellows of the ancient Egyptians—Bel-« lows blowers in the middle ages—Lantern bellows common over all the East—Specimens from Agricola—Used by negroes in the interior of Africa —Modern Egyptian blacksmiths’ bellows—Vulcan’s bellows—Various kinds of Roman bellows—Bellows of Grecian blacksmiths referred to in a prediction of theDelphic oracle—Application of lantern bellows as forcing pumps—Sucking and forcing bellows pumps—Modern domestic bellows of ancient origin—Used to raise water—Common blacksmiths’ bellows em-ployed as forcing pumps—Ventilation of mines.
Machines of the third dass described in this Book, are such as act bycompressure: the water is first admitted into close vessels and then for-cibly expelled through apertures made for that purpose. This is effectedin some by compressing the vessels themselves, as in bellows pumps—inothers by a solid body impinging on the surface of the liquid, as in fire en-gines—sometimes a column of water is used for the sarae purpose, atothers the expansive force of eompressed air. Of the last two, Heron’sfountain, air engines, and soda fountains, are examples. Strictly con-sidered, these machines have nothing to do with the pressure of the at-mosphere, (the active principle of those of the second dass,) but in prac-tice it is very generally employed. When the working cylinder of a for-cing pump is immersed in the water it is intended to raise, or when thelatter flows into it by gravity, it is a forcing pump simply; but when thecylinder is elevated above the water that supplies it, and consequently isthen charged by atmospheric pressure, the machine is a compound one,embracing the peculiar properties of both sucking and forcing pumps.The latter therefore differ from the former in raising water above theircylinders; and to elevations that are only limited by the strength of theirmaterials and the power employed to work them. They have been con-sidered by some writers as the oldest of all pumps. We shall considertheir varieties in the Order in which we suppose they were developed.
An intimate Connection has ever subsisted between the forcing pumpand the bellows; they are not only identical in principle, but every formadopted in one has been applied to the other. The bellows, from thesimple sack or skin employed by the negroes of Afriea to the complexand efficient instrument of China , and the enormous blowing machines of