212 



PUMP. 



Pump, the daily work of a man would be 139 cubic metres 

 ^**y*J of water raised a metre. 



M. Perronet found that an inclosed chain pump 

 raised in an hour 1998 cubic feet of water to the 

 height of 12 feet or 23976 cubic feet to the height of 

 ^ne foot. He mentions also that two inclined chain 

 pumps, driven by 36 horses, divided into several re- 

 lays, raised 1177-20 cubic feet of water to the height 

 of 15 feet, or 1765800 cubic feet to the height of one 

 foot ; and as a horse is equal to seven men, we have 

 7 X 36 = 252 men ; hence the daily work of one man, 

 as deduced from this experiment, is 7007 cubic feet of 

 water raised one foot. For farther details respecting 

 these experiments, see Hachette's Trails Elementaire 

 des Machines. 



18. Description of Trevethick's Temporary Forcer. 



Descrip- The object of this contrivance, which we owe to 

 tion of Mr. Trevethick, is to produce a constant stream in a 

 T re j^* common pump, and it consists in attaching to any pump 

 temporary ^^> ^'&' *&' an additional barrel CD, communicating 

 forcer. with the space between the two valves of the pump ; 

 Fig. 19. and in fixing the two pistons so that they may be 

 wrought at the same time. When the pistons are rais- 

 ed, the space BD below them is filled by the pressure of 

 the atmosphere, while the water above the piston of the 

 pump flows out at E. But when the pistons descend, 

 the valve v shuts, and consequently the water driven 

 by the piston b being unable to descend through v, 

 must ascend through the valve in the piston a, and 

 consequently produce a continued discharge from E 

 during the downward stroke of the pistons. See Nich- 

 olson's Journal, vol. ii. p. 216. 



19. Description of New sham's Fire Engine. 



Descrip- As the engines for extinguishing fire are nothing 

 tion of more than pumps for forcing out water in a continued 

 Newsham's stream, we shall make no apology for describing, in 

 fire engine. ^ s p] ace> the fire engine of Mr. R. Newsham, and 

 , LATE some other contrivances of the same kind. 

 No> | This engine consists of two pumps, A, B, Fig. 1, 2, 



Figs. 1, which are both sucking and forcing ones, whose pistons 

 and 2. are wrought by a double lever LL, fixed on the centre 



C of two arched heads, upon which the chains wind 

 and unwind, as the pistons a, b, to which they are at- 

 tached, rise or fall. When one of the pistons is raised, 

 the water from the reservoir R follows it into the bar- 

 rel, through the valve v. But when the same piston is 

 depressed, the valve v shuts, and the water in the bar- 

 rel is forced through the valve x into the air vessel 

 W W, into which a pipe P P' is inserted, and reaches 

 near to the bottom of the vessel. The same effect is 

 produced by the other piston, with this difference only, 

 that while the one piston is rising and sucking water 

 from the reservoir, the other is forcing into the air ves- 

 sel the water which it had raised into the barrel by its 

 previous ascent. As soon as the water has risen in the 

 air vessel above the end P' of the pipe P P', it is ob- 

 vious that the air included in the vessel must be corn- 

 pressed by every new quantity of water that is forced 

 into it, and when the water has risen to a considerable 

 height in it, the elasticity or spring of the air reacts 

 powerfully on the surface m n of the water in the air- 

 vessel, and compels it to ascend through the pipe' P P, 

 through a long flexible leather pipe called the hose, 

 screwed in at P, from the extremity of which it moves 

 with great force, and may be directed, in consequence of 

 the flexibility of the leather pipe, to any part of a house 



on fire. When more than two men are to work the levers 

 LL, a sort of frame work is attached to the engine, by 

 the cross-bars G H, and treddles are also added, by 

 which the workmen act with their weight in treading. 

 The side trough, into which the water is first poured, 

 is shown at Z. It enters the reservoir R through a cop- 

 per grating e d, leaving any sand, dirt, or stones with 

 which it may be mixed, in the pump. At X Y is seen 

 the handle of a cock E, which may be turned into three 

 different situations. The first is used when there 

 is water near at hand to work the engine by the suck- 

 ing pipe S, in which case the water enters at S, and 

 rises through the valve v, and there is no communica- 

 tion between the barrels and the reservoir R. In the 

 second position of the cock, there is no communication 

 between the barrels and the end S of the sucking pipe ; 

 but the water from the reservoir R enters the cock E 

 sidewise, and turning at right angles through the cock 

 towards v, enters the pumps. The third position is 

 that in which there is no communication, either with 

 the sucking pipe S, or with the reservoir R, but only 

 a communication between the reservoir R and the suck- 

 ing pipe S, which is the position when the engine is 

 done working, to empty the water left in the cavity of 

 the cistern. 



The following table shows the law according to 

 which the elasticity of the air will act on the surface of 

 the water in the air vessel : 



Pump. 



7* * * , -. \ * 



. n In 1)33 



n 



For a complete and detailed account of Newsham's 

 fire engine, see Desagulier's Experimental Philosophy, 

 vol. ii. p. 505. 



20. Description of another Fire Engine. 



This fire engine, which is now in use, is constructed Descrip- 

 on the principle of some of the pumps proposed by tion < )f 

 Ramelli, and which we shall describe in the next sec- another 

 tion. It is represented in Fig. 4, and is wrought fue en 8"' e - 

 by the levers LL. The interior mechanism is shown p jg 4. 

 in Fig. 3, where CD is the piston working tight 

 in the cylindrical barrel EFD, and moved by the 

 levers LL. When the piston CD is in the position 

 shown in Fig. 3, the water ascending the main M, Fig. 3. 

 rises through the valve v, and enters by the opening 

 A into the barrel ED. The motion of the piston 

 CD from D to A then closes the valve v, and forces 

 the water between D and E up through the valve 

 x into the air vessel at W. When CD quits the 

 side B of the barrel, the water follows it, rushing in 

 through the valve y, and the aperture B, and when CD 

 returns again towards B, it forces up this water through 

 the valve z into the air vessel, as it cannot return to- 

 wards M by the valve y, which closes on the return of 

 CD towards B. 



In constructing the hose or leathern pipes of fire en- 

 gines, it was customary to sew them together, and 



