Fig. 5 represents a longitudinal section, and Fig. 6 an end view of the air chamber A, and the contained pump P, p the piston, S the stuffing box of the piston rod, h, h, valve holes, through which the water is driven into the air cham ber, those by which it is received into the pump not being visible in the first projection, but V in Fig. 6 is the front entering valve, and D the discharging valve, over this is the diaphragm d. From the general similarity of construc tion in fire engines, it is unnecessary to enter into further details. The vignette figure 1, represents a hydraulion peculiarly suited for villages, and adapted to the power of sixteen men, the pump being seven inches in diameter and the stroke of the piston 9 inches. Twenty men are suffi cient to furnish the requisite supply of water, and to put the whole apparatus into complete and effectual operation. The short piece of hose attached to the pump nozle in the manner delineated, indicates a simple but very useful mode of employing the head of water raised to the inser tion of the pump handle, and for impelling the water from the pump through hose to the engine.
The larger sized hydratilions are supported on springs, which greatly facilitate their motions over rough roads or pavements, and prevent many injuries which might occur. They are constructed in such a manner as to be very or namental, and generally have two reels, in which case the engine is placed in the centre of the body.
When fire engines are constructed to raise the water as from a pond, by suction, it is obvious that the pipes through which the water is raised must be perfectly air tight. Leather hose distended by a series of metal rings, but re taining. some degree of flexibility, and divided into short sections, connected by screws, were usually employed for the purpose. The operations of the engine, however, were often defeated by warble holes or other small defects in the hose, through which the air would enter, and pre vent the ascension of the water. This inconvenience has been completely obviated by a plan of Sellers and Pennock, which substitutes metal tubes with joints, instead of such hose, as repr csented in Fig. 7. These tubes are connected to the caps C, C, Fig. 7 and 8, the caps being drawn together by the rod R, and swivelled jointed at J, J, by means of a tongue on one, that revolves in a groove in the other cap. Suctions thus simply constructed accommodate them selves with more facility to the position they are to occupy when in use, than the leather pipes, which only bend in a long curve; they are certainly air tight, are much lighter, and fold up so as to be carried in a birth under the engine, without taking them apart at the joints, which has to be done with the ordinary suction hose to render them por table.
For farther information on the subject of fire-engines, see Phil. Trans. 1676, vol. xi. p. 679. Reaumur's engine Mem. Acad. Par. 1722 ; Machines Approuvees, torn. i. p. 151. Ublemann's engine, Mem. Acad. 1722, and Mach. Approuv. tom. iv. 35. Gensanne's engine, Mach. .4pprouv. tom. vii. 95. Thillay's engine, Men/. Aced. 1746, Iltst. 120. Bonnet's engine, Mem. Aced. 1749, Hist. 182. Dearborn's engine, Meat. Amer. Acad. of Arts, 1794, vol. i. p. 520. Bramah's engine, Repertory of Arts", vol. iii. p. 368. Simp kin's engine, Repertory of Arts, vol. vii. p. 301. See also Belidor's Architect. Hydraul. vol. ii. p. 186. Emerson's Mechanics, p. 275. An account of the history of fire engines, by Beckmann, will be found in the Phil. Meg. vol. xi. p. 238, or in his Hist. of Inventions, vol. iv. p. 75.
22. Description of various Pumps,by Ramelli and others As these different pumps all resemble one another in principle, we shall describe them under the same section. They are represented in Plate CCCCLXXI. Figs. 7, 8, 9, and 10.
In Fig. 7, AB is a lever moving round C as a centre. The end BC works in a box CBF, immersed in the water `VW. 'When AC is pulled to the left, the end BC forces out the water up the pipe E and through the valve v into the pipe Ev, where it is kept by the descent of the valve The water enters the box by an aperture below B.
In Plate CCCCLXXI. No. III. Fig. 8. a wheel A, with three spiral wings, B, C, D, revolves round A in the centre, and is immersed in the water NVW. When C ascends towards F, the water between C and F is forced up into the pipe JIG, and is detained by the descent of the valve v, the rod FE rising between the guides or rollers inn as c advances to F, for the purpose of preventing the water from getting through at F. The next wing D produces the same effect, carrying up the water above its natural level \V"tV to the pipe H.
In Fig. 9, which is taken from the cabinet of Servier, there are two revolving wheels AB, which work, in one another, and arc pulled close to the elliptical cistern DC. The water which rises through the pipe E into C is forced by these wheels round the outer teeth up to I), and conse quently up the pipe F. Ramelli had previously given a pump of this kind, in which there was only one wheel, with a rod like EF in Fig. 27. Sec .1Vicholson's vol. viii. p. 35.