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part of the barrel from which it is moving; the air relation between the power expended and the work contained in which becoming rarefied, by having to produced, as measured by the water raised-we occupy a greater space, exerts less pressure on the may remark, that the power is expended -- 1st, in valve D at the bottom of the barrel than the air in raising the water through the required height; 2d, suction-pipe B below it. This valve is thus opened, in overcoming the friction of the moving parts
and the air from the suction of the pump; 3d, in the friction and fluid resistance
and by the laws of fluid-
Fig. 4. of the water in the suction-pipe, the water will rise in it, until the pressure on its surface, plus the instead of being fixed on the piston, is placed in weight of its fluid column, balances the pressure of the discharge-pipe, the piston itself being solid. the atmosphere on the surface H outside; so that, The water is drawn up into the barrel by suction as the air in the suction-pipe is rarefied, the water in the manner just described in the suction-pipe, rises in it, until, when all the air is extracted from and then the pressure of the piston in its downit, the water stands at the level of the valve D. ward-stroke forces it through the valve E to any By the next upward stroke of the piston, the barrel height that may be required. That shewn in fig. 4 being emptied of air, the water follows the piston, is provided with a different description of piston, and fills the barrel as it filled the suction-pipe. The called the plunger-pole. Its action is precirely the pressure produced by the downward stroke shuts same as that of the other, with this exception, that the valve D, and forces the water in the barrel the plunger-pole, instead of emptying the barrel at through the valve E. The succeeding upward stroke every stroke, merely drives out that quantity which carries this water into the pipe above, and again it displaces by its volume. It is simply a solid rod fills the barrel from the suction-pipe. In like of metal, A, moving through a water-tight stuffing. manner, every successive upward stroke discharges box, B. This stuffing-box is made by placing, on a a body of water equal to the content of the barrel circular flange of metal, rings of india-rubber or into the pipo above it, and the pump will draw other packing, the inner diameter of which is water as long as the action of the piston is con slightly less than that of the plunger-pole On tinued.
The action of this pump may be more shortly whole are passed bolts, which, on being screwed described by saying that the piston withdraws the tight, force the packing tightly against the plungerair from the barrel, and produces a vacuum, into pole. It possesses many advantages, for the packing which the water rushes through the suction-pipe, can be tightened and repaired without removal of impelled by the pressure of the atmosphere on its the piston or stoppage of the pump; also, the surface. This atmospheric pressure balances a cylinder is not worn by its action, nor does it column of water of about 33 feet in height; so that require to be accurately bored out, as in the other if the barrel be placed at a greater height than this form of pump. from the surface of the water in the well, the water. In these pumps, it will be observed that the will not rise into it, and the pump will not draw. water is forced into the ascending pipe cr column.
With regard to its efficiency—that is to say, the only on the downward stroke; it will thus be
discharged in a series of rushes or jerks. As it is a sense, as a means of producing a given result with the
the pressure, and renders box. Fig. 6 shews an example of this pump, which
is worked by a rod B of
piston itself. During the
space D, which would other.
wise be left empty by the
descent of the piston; the other volume is sent into the ascending column; so that a volume of water equal to half the content of the barrel is sent into the ascending column by both the up and the down strokes.
A pump of enormous power, simple and economical, has recently been invented by Mr Thos. Shaw, of Phila., and manufactured by the Hydrostatic and Hydraulic Company of Penna. It consists of an iron pipe, in the centre of which revolves a steel shaft, furnished at intervals of three feet with blades or propellers, inclined at an angle of 65°, and revolving with the shaft. Midway between these blades, but attached to the walls of the pipe, are wings or blades of the same pitch, at a
Fig. 6.—Murray's Chain-pump. reversed angle. On revolving the shaft, a continuous stream of water, 20 inches in diameter, flows from the the ease of its construction and erection, and its elevator, at the rate of 10,000 gallons per minute, from admirable efficiency even at considerable heights. a depth of 300 feet. The manufacturers assert that In this pump, the friction is reduced by having only these pumps cost much less and can lift more foot-| 3 or 4 lifts instead of 20 or 30, as was previously the pounds of water per 100 pounds of coal consumed than case. The chains pass under a roller, A, at the foot, other pumps of the same power. For notices of lifting, and are driven by a small pitch-wheel, B, at the top, centrifugal, and turbine pumps, see Machinery, &c., in over which they are conducted, and which is driven The Industrial Arts, by F. A. P. Barnard, in Rep. of by appropriate gearing. The lifts feather in passing
In spite of the great antiquity of the lift and unfold when brought round to the ascending side ; force pump, it is only of late years that improve- thus the pump is enabled to take off the water with ments have been introduced into its construction the same dip as other pumps. The pump is not capable of rendering it an efficient machine-that is, liable to be choked, as a back turn of the chain one which returns in the shape of water raised, a immediately releases any substance getting between good proportion of the power applied to it. In 1849, the lift and the barrel. The speed is variable, in M. Morin found by experiments that the power lost proportion to the duty required. The speed at was 55 to 82 per cent.--that is to say, that of the which the chain is ordinarily worked is from 200 to motive-power, 45 per cent. was yielded in the best 300 feet per minute. The greatest lift yet made by and 13 in the worst, giving an average of about 30 | Murray's chain-pump is 60 feet high ; but it is conper cent. In 1851, the jury, reporting on those sidered that 100 tons of water per minute could be exhibited in the Great Exhibition, say that it is one raised 100 feet high. From 10 to 12 feet apart has of our worst machines, considered in a mechanical ) been found to be the best pitch for the lifts; putting
them nearer, needlessly increases the friction. Expe- leaves the circumference of the wheel, and enters riments made by Mr Lovick for the Metropolitan the circular whirlpool chamber F; so that the Board of Works, shewed that the slip of the lifts interior of the pump may be looked on as a whirl. which work in the barrel, and are one-eighth of an | pool, extending from the axle of the wheel to the inch shorter each way than the barrel, averaged 20 per circumference of the whirlpool chamber. Into this cent. of their motion, and that the useful work done I whirlpool the water is drawn at the central orifice averaged 63 per cent of the indicator horse-power of of the wheel, and discharged by the pipe G at the the engine working it.
circumference of the whirlpool chamber; and the 4. The Centrifugal Pump.--These pumps, with ref. force with which it is discharged, or the height to erence to those previously described, may be called, which it will rise in the pipe G, is measured by the new, as, though they have been in use in one form or centrifugal force of the water revolving in the another for at least a century, their merits were not whirlpool. brought prominently forward till the year 1851, when With reference to the efficiency of these pumps, the great efficiency of the models exhibited by Messrs it is impossible to give any accurate estimate, since Appold, Gwynne, and Bessemer drew general attention as high as 70 per cent. of the applied power is to the subject.
claimed to be returned by forms of the pump shewn The essential parts of this pump are-1. The wheel in figs. 7 and 8, while some other descriptions expeto which the water is admitted at the axis, and from rimented on in 1851 gave only 18 per cent. of useful which it is expelled at the circumference, by the cen- effect. trifugal force due to the rotatory motion imparted to It will be evident, from the above description it in passing through the rapidly revolving wheel; and of the pump, that the height to which the water 2. The casing or box in which the wheel works, and will be raised depends entirely upon the speed of by which the entering water is separated from that revolution of the wheel ; and it is by this that the discharged.
application of centrifugal pumps is limited to com. Figs. 7 and 8 are a section and plan of a cen- paratively low lifts of say less than 20 feet, as the trifugal pump. The water enters the pump by the speed for high lifts requires to be greater than can
be conveniently and usefully attained in practice. They are best applied when raising large quantities of water through low lifts. It will also be observed, that on account of the simplicity of their parts, and the absence of valves, they are much less liable than other pumps to be choked by the entrance of solid materials. In some descriptions of this pump, the exterior whirlpool chamber is dispensed with; and to the vapes of the wheel is given such a curvature backwards from the direction of motion, that the water leaving the circumference of the wheel is spouted backwards from the vane-passages with a speed equal to that of the wheel in the opposite direction, so that it has only a radial motion with reference to a fixed object; in other words, that the force is acquired from the radial component of the pressure of the vanes, instead of the centrifugal force of the revolving water. Those pumps, how
ever, give the best results which, as the one above Fig. 7.
described, combine both actions. In all cases,
curved vanes are much superior to straight ones. supply-pipes A, A, which lead to the central orifices |
15. The Jet-pump.--This pump is worked by of the wheel B, B; it then passes through the pas-water-powe
water-power, and is worthy of notice on account of sagas C, C, formed by the vanes and the side cover
the extreme simplicity of its parts, and of not ing-plates, 1), of the wheel. In passing through
requiring the care of an attendant while in operation.
Fig. 9 is a representation of this pump, C is the water which it is required to raise to the level of the water D, and B is the water in the stream available for working the pump. The water B passes down the pipe A, and is discharged from the jet or nozzle, E, into the conical pipe F. Round the nozzle is the vacuum-chamber G, at the bottom of which is attached the conical pipe F, and into the side of which the suction-pipe H enters from the water to be pumped. The water, in passing from the nozzle into the conical pipe, carries air with it, and so gradually forms a vacuum in the chamber G, when the water rises into it from the level C, through the pipe H; and it is in turn carried with the jet down the conical pipe into the dischargelevel D. The velocity of the water coming from the jet is gradually retarded by the action of the conical pipe, the speed decreasing as the area of section
increases; and the vis viva of its motion is by this Fig. 8.--Thomson's Centrifugal Pump. retardation converted into a sucking force, drawing
the water from the suction-pipe through the vacuum these passages of the wheel, which is made to chamber into the conical pipe. The water issuing revolve by power applied to the shaft E, it acquires from the jet will have a speed equal to that proa rotatory motion, which still continues when it duced by a column of the height BC, or the sum of
the fall and lift. This pump may be viewed, for name of a witty buffoon of Acerra who joined a purposes of explanation, as a syphon, into the company of players and became the favourite of the si orter leg of which a jet of water is injected, Neapolitan populace. Others give his original name
as Paolo Cinella. The variety and inconsistency of
The drama or play in which the modern P. figures, is ascribed to an Italian comedian, Silvio Fiorillo, about 1600. The exhibition soon found its way into other countries, and was very popular in Eng. land in the 17th century. Its popularity seems to have reached its height in the time of Queen Anne, and Addison has given in the Spectator a regular criticism of one of the performances. The scenes as now given by the itinerant exhibiters of the piece are much shortened from what were originally performed, in which allusions to public events of the time were occasionally interpolated. The fol.
lowing is an outline of the plot as performed Fig. 9.
in 1813. Mr P., a gentleman of great personal
attraction, is married to Mrs Judy, by whom he which overcomes the pressure due to the difference has a lovely daughter, but to whom no name is of levels, and reverses the ordinary motion of the given in this piece, the infant being too young to water in a syphon. An efficiency of 18 per cent. has be christened." In a fit of horrid and demoniac been obtained from this pump, which is low, as į jealousy, P., like & second Zeluco, strangles his compared with that obtained from other descrip
beauteous offspring. Just as he has completed his tions of pump; yet in cases where waste of water
dreadful purpose, Mrs Judy enters, witnesses the power is not so much to be avoided as expense in
brutal havoc, and exit screaming ; she soon returns, erecting, working, and maintenance, these pumps however, armed with a bludgeon, and applies it to possess decided advantages. The case to which her husband's head, ' which to the wood returns a They are peculiarly applicable is the drainage of wooden sound.' P. at length exasperated marshes, which have streams of water adjacent to another bludgeon, soon vanquishes his already. them descending from a higher level.
weakened foe, and lays her prostrate at his PUN is the name given to a play upon words.
feet; then seizing the murdered infant and the
expiring mother, he flings them both out of the The wit lies in the equivocal sense of some parti.
window into the street. The dead bodies having cular expression, by means of which an incon
been found, police-officers enter the dwelling of gruous, and therefore ludicrous idea is unexpectedly | shot into the sentence. One or two examples will
P., who flies for his life, mounts his steed; make the matter clearer than any definition. Two
and the author neglecting, like other great poets, persons looking at a beggar-boy with an extraordi.
the confining unities of time and place, conveys nary big head What a tower !' cried the first. in
his hero into Spain, where, however, he is arrested
by an officer of the terrible Inquisition. After •Say, rather,' replied the second, what a fort o'
enduring the most cruel tortures with incredible lice' (fortalice).- A noted punster was once asked, with reference to Mr Carlyle's writings, if he did
i fortitude, P., by means of a golden key, opens his not like to expatiate in such a field. "No,' was
prison-door, and escapes. The conclusion of the
story is satirical, allegorical, and poetical. The hero the felicitous rejoinder; "I can't get over the style' |
is first overtaken by Weariness and Laziness in the friend that her husband (whose business had taken him to the far West) constantly sent her letters
Disease, in the disguise of a physician, next arrests filled with expressions of endearment, but no money, I did
him; but P. sees through the thin pretence,' and
in was told, by way of comfort, that he was giving her i Death at length visits the fugitive : but Plays
y, disnisses the doctor with a few derogatory kicks. a proof of his unremitting affection!
| about his skeleton carcass so lustily, and makes PUNCH, the chief character in a popular comic the bones of his antagonist rattle so musically with exhibition performed by means of Puppets (q. v.). a bastinado, that · Death his death's blow then Various accounts are given of the origin of the received. Last of all comes the Devil ; first under name. The exhibition is of Italian origin, and the the appearance of a lovely female, but afterwards Italian name is Pulcinella, or Policinella. Accord in his own natural shape, to drag the offender to ing to one story, a peasant, a well-known character the infernal regions, to expiate his dreadful crimes. in the market-place of Naples, got the name Even this attempt fails, and P. is left triumPulcinelli from dealing in fowls (pulcinelli), and phant over Doctors, Death, and the Devil. The after his death was personated in the puppet-shows curtain falls amid the shouts of the conqueror, who, of the San-Carlino theatre. Another account makes on his victorious staff, lifts on high his vanquished the word corruption of Puccio d'Aniello, the foe.