P U F 



205 



P U M 



"'<". Baron Puffendorf died at Berlin in U)'9i, of an in- 

 lamuei. flammation in his feet, occasioned by cutting his nails, 

 and left behind him a high reputation for integrity and 

 honour. 



His other works, besides those we have men- 

 tioned, are, An Introduction to the History oj' the prin- 

 cipal States at present in Europe, with a Continua- 

 tion ; and an Abridgment ef his Treatise on the Law 



of Nature and Nations, entitled, Dutiet of a Ulan and 

 a Citizen. 



His elder brother Isaiah, who died in 1689, "* the 

 author of a satirical work, entitled, Anecdote* of 

 Sweden, or a Secret Hittory of Charles XL 



ULLEY. See MECHANICS, Vol. XIII. p. 525. 



PUMICE STONE. See MINERALOGY, /ETNA, and 

 VOLCANO. 



PUMPS. 



Descrip- 

 tion of the 

 sucking 

 pump. 

 PLATE 



CCCCLXX. 



Fig. 1. 



Pump. PUMP is the name given to a well known engine for 

 raising water above its natural level. It was invented 

 by Ctesibius, as we have already stated in our Histon/ 

 of HYDRODYNAMICS, but has received many improve- 

 ments in modern times. In giving an account of the 

 most important variations which this engine has under- 

 gone, we shall begin by describing the three forms in 

 which it generally appears, viz. the sucking pump; the 

 lifting pump; and the forcing pump. 



1. Description of the Sucking Pump. 



The sucking pump is represented in Plate CCCCLXX. 

 Fig. 1. where ABDC is called the barrel, and CDEP 

 the suction pipe, which are joined to one another by 

 flanges at CD, (if they are made of cast iron,) so as to 

 be perfectly air tight. The lower end of the suction pipe 

 is immersed in the water to be raised, and generally has a 

 grating across it to prevent the entrance of extraneous 

 substances. The piston cd, attached to the lower end of 

 the spear or rod a b, is a hollow cylinder, and has its 

 exterior circumference formed of leather, so as to move 

 tightly in the barrel ABCD, without permitting any 

 air to pass between it and the barrel. 



In the centre of the piston there is placed a valve v 

 opening upwards, and at CD another x of the same kind, 

 the construction of which is shown in Figs. 2. and 3. 

 Figs. 2, 3. i n pig. 3. CD corresponds with CD in Fig. 1, and 1, 

 2, 3, 4, are the screw holes of the flanges. Upon this 

 plate, with a part NL cut out, there is applied a ring 

 of thick leather NKL ; and another piece of strong lea- 

 ther NR, composing the valve, has its end N placed in 

 the opening NL. The circular part of the leather or 

 valve NR, is of a greater diameter than the opening 

 in the leather NKL, but is not so great as to fill up 

 the circle OKI, Fig. 3. Two brass plates, the upper- 

 most of which is seen at R, are used to strengthen this 

 valve, the under one being a little smaller than the 

 aperture in the valve plate, and the upper one a little 

 larger than that aperture. 



When this plate is inserted at CD, the tail of the 

 leather valve at N will be compressed between the 

 plates, and will become a hinge, on which the valve 

 can rise or fall. A valve nearly similar is placed at u. 



The operation of the pump will now be readily un- 

 derstood. When the piston c d is depressed towards 

 CD by the power of a man working at the rod or spear 

 a b, the air between c d and CD forces up the valve v, 

 and occupies the space passed through by the piston 

 c d ; but upon drawing up the piston towards AB, the 

 pressure of the air above c d shuts the valve, and con- 

 sequently all the air in the barrel below c d, and in the 

 suction pipe, is rarefied. The atmospheric air being 

 no longer balanced by that in the pipe, the equilibrium 

 can only be restored by the water at the bottom of the 



suction pipe rising a little in that pipe. By depressing p u mp. 

 the piston a second time, and again drawing it up, the v^-y-^ 

 air below c d is again rarefied, and the water rises a lit- 

 tle higher in the suction pipe, till by successive strokes 

 of the piston the water rises through the valve, and 

 pressing the valve down by its weight remains there. 

 If the piston is now made to descend in the water above 

 CD, it will rise through the valve v, and will be lifted 

 up by raising the piston into the reservoir MN, from 

 which it may be conveyed by a spout or pipe for use. 

 Hence it is obvious, that whenever the piston c d i* 

 raised, the valve x will rise, and the valve v fall, and vice 

 versa. As the whole pressure of the atmosphere is 

 equal to about a column of water of 32 feet, the perpen- 

 dicular height of the piston cd above the surface of the 

 water in the well must never exceed 32 feet. 



2. Description of the Lifting Pump. 



The lifting pump, which, properly speaking, is only Detcrip- 

 the sucking pump inverted, is shown in Fig. 4. In this lion of the 

 pump, the spear or rod of the pump consists of a frame lifting 

 a in b, anb, to which is fixed the piston c d, with its P um P- 

 valve v opening upwards. At the flange CD there is CC ^ CLXX , 

 also another valve x opening upwards. pjg. 4. 



Let this apparatus be now immersed in water, whose 

 surface is W W, and let the piston be drawn up to CD. 

 When the piston is permitted to descend by its own 

 weight, the valve v will open, and the water will rise 

 till it fills the barrel. If the piston is now drawn up 

 by a power at a, the valve v will shut, and the piston 

 c d will push the water upward through the valve x, 

 into the rising pipe or main CDEF. By again letting 

 down the piston, the valve x will shut by the weight 

 of the superincumbent water, and the water below will 

 again rise into the barrel through the valve v. 



3. Description of the Forcing Pump. 



The forcing pump, represented in Plate CCCCLXX. Deacrip- 

 Fig. 5. consists of a working barrel ABCD, a suction t'n of the 

 pipe CDEF, and a main or rising pipe DGH. The fc 

 piston c d, fixed to the spear or rod a b, is solid, and 

 forms a kind of double cone, which is widest at the 

 middle, being covered with two hoops of strong leather. 

 At CD there is a valve v rising upwards, and another 

 x of the same kind in the rising pipe at ef. 



When the piston a b cd is pushed downwards, it 

 drives the air before it, closing the valve v, and open- 

 ing the valve x. Upon drawing up the piston, the air in 

 the space Dfe now expands in the barrel, and the valve 

 x is shut by the superior pressure of the atmosphere. 

 From the rarefaction of the air in the barrel the equi- 

 librium of the air above and below the- valve v is de- 

 stroyed, and consequently the predominating pressure 



CC CCLXX. 

 FI. 5. 





