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PUMPS.

2. The Lift and Force Pump.-Figs. 3 and 4 represent two varieties of this pump. That shewn in fig. 3 is very similar to the suction-pump before described, with this exception, that the valve E,

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 pipe enters the barrel; so of the water in passing through the valves and pipes; that when the piston has 4th, in the losses arising from the want of proper arrived at the top, a volume proportion between the various parts of the pump. of air equal to the contents The losses arising from these last sources are very of the barrel has passed great, and vary so much according to the confrom the suction-pipe into struction of each particular pump, that no useful the barrel. When the piston estimate can be formed of the efficiency. We may descends, it compresses the say, however, that a pump of this description, to air in the barrel, which shuts yield 50 per cent. of the applied power, must be the valve D; and when the well proportioned and carefully constructed. C density of the compressed air becomes greater than that of the atmosphere, the valve E in the piston is forced open, and the air in the barrel passes to the upper side of the piston. The next upward stroke of the piston again draws a like quantity of air from the suction-pipe into the barrel; and, as none of this air again enters the pipe, but is passed to the upper side of the piston by its downward stroke, the suction-pipe is by degrees emptied of the air it contained. During this process, however, motion has taken place in the water at the foot of the suction-pipe. The surface of the water at His pressed upon by the weight of the atmosphere with a pressure of about 15 lbs. on every square inch; and by the laws of fluidpressure, if an equal pressure is not exerted on the surface of the water in the suction-pipe, the water will rise in it, until the pressure on its surface, plus the weight of its fluid column, balances the pressure of the atmosphere on the surface H outside; so that, as the air in the suction-pipe is rarefied, the water rises in it, until, when all the air is extracted from it, the water stands at the level of the valve D. By the next upward stroke of the piston, the barrel being emptied of air, the water follows the piston, and fills the barrel as it filled the suction-pipe. The pressure produced by the downward stroke shuts the valve D, and forces the water in the barrel through the valve E. The succeeding upward stroke carries this water into the pipe above, and again fills the barrel from the suction-pipe. In like manner, every successive upward stroke discharges a body of water equal to the content of the barrel into the pipo above it, and the pump will draw water as long as the action of the piston is continued.

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Fig. 2.

The action of this pump may be more shortly described by saying that the piston withdraws the air from the barrel, and produces a vacuum, into which the water rushes through the suction-pipe, impelled by the pressure of the atmosphere on its surface. This atmospheric pressure balances a column of water of about 33 feet in height; so that if the barrel be placed at a greater height than this from the surface of the water in the well, the water will not rise into it, and the pump will not draw.

With regard to its efficiency-that is to say, the

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Fig. 3.

Fig. 4.

instead of being fixed on the piston, is placed in
the discharge-pipe, the piston itself being solid.
The water is drawn up into the barrel by suction
in the manner just described in the suction-pipe,
and then the pressure of the piston in its down-
ward-stroke forces it through the valve E to any
height that may be required. That shewn in fig. 4
is provided with a different description of piston,
called the plunger-pole. Its action is precurely the
same as that of the other, with this exception, that
the plunger-pole, instead of emptying the barrel at
every stroke, merely drives out that quantity which
it displaces by its volume. It is simply a solid rod
of metal, A, moving through a water-tight stuffing-
box, B. This stuffing-box is made by placing, on a
circular flange of metal, rings of india-rubber or
other packing, the inner diameter of which is
slightly less than that of the plunger-pole.
these is placed a ring of metal, and through the
whole are passed bolts, which, on being screwed
tight, force the packing tightly against the plunger-
pole. It possesses many advantages, for the packing
can be tightened and repaired without removal of
the piston or stoppage of the pump; also, the
cylinder is not worn by its action, nor does it
require to be accurately bored out, as in the other
form of pump.

On

In these pumps, it will be observed that the water is forced into the ascending pipe cr column. only on the downward stroke; it will thus be

PUMPS.

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discharged in a series of rushes or jerks. As it is a sense, as a means of producing a given result with the great object to procure a continuous discharge, both least possible expense of power. In those exhibited for its convenience, and for the saving of the power in the International Exhibition of 1862, we find wasted by the continual acceleration and retarda-marked improvement. The jury report that 'a large tion of the ascending column, various methods have number of constructers have sought to give the waterbeen used for that purpose. The most common is ways and valves dimensions which render as small as the reservoir of air, which is an air-tight receptacle possible the loss of power by friction. They have also fixed vertically on the discharge-pipe; the water sought to give a continuous movement to the ascendforced into the pipe by the down-stroke compresses ing column of water, independently of the action of this air, which, acting as a spring, returns this force the reservoir of air.' to the ascending column during the period of the 3. The Chain-pump. This pump is formed in up-stroke, and so, by taking the blow of the enter- general of plates of wood fastened to an endless iron ing water, and returning it gradually, equalises chain, and moving upwards in a rectangular case or the pressure, and renders box. Fig. 6 shews an example of this pump, which the discharge uniform. was exhibited in the International Exhibition of Another method is the 1862, called 'Murray's Chain-pump ;' a pump which double-action force-pump, is very much used on public works, on account of by which equal volumes of water are forced into the ascending column by both up and down strokes. example of this is shewn in fig. 5. The solid piston A is worked by a rod B of half the section of the piston itself. During the up-stroke, the upper surface forces a volume of water into the ascending column, and the lower surface draws in twice that volume. In the down-stroke, these two volumes are sent through the pipe E into the receptacle C, communicating with the upper face of the piston. One of the volumes fills 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.

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Fig. 5.

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 reversed angle. On revolving the shaft, a continuous stream of water, 20 inches in diameter, flows from the elevator, at the rate of 10,000 gallons per minute, from a depth of 300 feet. The manufacturers assert that these pumps cost much less and can lift more footpounds of water per 100 pounds of coal consumed than other pumps of the same power. For notices of lifting, centrifugal, and turbine pumps, see Machinery, &c., in The Industrial Arts, by F. A. P. Barnard, in Rep. of Am. Com, to the Paris Üniv. Exhib., Washington, 1870. In spite of the great antiquity of the lift and force pump, it is only of late years that improvements have been introduced into its construction capable of rendering it an efficient machine-that is, one which returns in the shape of water raised, a good proportion of the power applied to it. In 1849, M. Morin found by experiments that the power lost was 55 to 82 per cent.-that is to say, that of the motive-power, 45 per cent. was yielded in the best and 18 in the worst, giving an average of about 30 per cent. In 1851, the jury, reporting on those exhibited in the Great Exhibition, say that it is one of our worst machines, considered in a mechanical

Fig. 6.-Murray's Chain-pump.

the ease of its construction and erection, and its admirable efficiency even at considerable heights. In this pump, the friction is reduced by having only 3 or 4 lifts instead of 20 or 30, as was previously the case. The chains pass under a roller, A, at the foot, and are driven by a small pitch-wheel, B, at the top, over which they are conducted, and which is driven by appropriate gearing. The lifts feather in passing over the wheel to the descending side, and only unfold when brought round to the ascending side; thus the pump is enabled to take off the water with the same dip as other pumps. The pump is not liable to be choked, as a back turn of the chain immediately releases any substance getting between the lift and the barrel. The speed is variable, in proportion to the duty required. The speed at which the chain is ordinarily worked is from 200 to 300 feet per minute. The greatest lift yet made by Murray's chain-pump is 60 feet high; but it is considered that 100 tons of water per minute could be raised 100 feet high. From 10 to 12 feet apart has been found to be the best pitch for the lifts; putting

PUMPS.

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them nearer, needlessly increases the friction. Experiments made by Mr Lovick for the Metropolitan Board of Works, shewed that the slip of the lifts which work in the barrel, and are one-eighth of an inch shorter each way than the barrel, averaged 20 per cent. of their motion, and that the useful work done averaged 63 per cent. of the indicator horse-power of the engine working it.

4. The Centrifugal Pump.-These pumps, with reference to those previously described, may be called, new, as, though they have been in use in one form or another for at least a century, their merits were not brought prominently forward till the year 1851, when the great efficiency of the models exhibited by Messrs Appold, Gwynne, and Bessemer drew general attention to the subject.

The essential parts of this pump are-1. The wheel to which the water is admitted at the axis, and from which it is expelled at the circumference, by the centrifugal force due to the rotatory motion imparted to it in passing through the rapidly revolving wheel; and 2. The casing or box in which the wheel works, and by which the entering water is separated from that discharged.

Figs. 7 and 8 are a section and plan of a centrifugal pump. The water enters the pump by the

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leaves the circumference of the wheel, and enters the circular whirlpool chamber F; so that the interior of the pump may be looked on as a whirlpool, extending from the axle of the wheel to the circumference of the whirlpool chamber. Into this whirlpool the water is drawn at the central orifice of the wheel, and discharged by the pipe G at the circumference of the whirlpool chamber; and the force with which it is discharged, or the height to which it will rise in the pipe G, is measured by the centrifugal force of the water revolving in the whirlpool.

With reference to the efficiency of these pumps, it is impossible to give any accurate estimate, since as high as 70 per cent. of the applied power is claimed to be returned by forms of the pump shewn in figs. 7 and 8, while some other descriptions experimented on in 1851 gave only 18 per cent. of useful effect.

It will be evident, from the above description of the pump, that the height to which the water will be raised depends entirely upon the speed of revolution of the wheel; and it is by this that the application of centrifugal pumps is limited to comparatively low lifts of say less than 20 feet, as 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 vanes 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, however, give the best results which, as the one above described, combine both actions. In all cases, curved vanes are much superior to straight ones. 5. The Jet-pump.-This pump is worked by water-power, and is worthy of notice on account of the extreme simplicity of its parts, and of not requiring the care of an attendant while in opera

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tion.

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 retardation converted into a sucking force, drawing the water from the suction-pipe through the vacuum chamber into the conical pipe. The water issuing from the jet will have a speed equal to that produced by a column of the height BC, or the sum of

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PUN-PUNCH.

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which overcomes the pressure due to the difference of levels, and reverses the ordinary motion of the water in a syphon. An efficiency of 18 per cent. has been obtained from this pump, which is low, as compared with that obtained from other descriptions of pump; yet in cases where waste of waterpower is not so much to be avoided as expense in erecting, working, and maintenance, these pumps possess decided advantages. The case to which they are peculiarly applicable is the drainage of marshes, which have streams of water adjacent to them descending from a higher level.

PUN is the name given to a play upon words. The wit lies in the equivocal sense of some particular expression, by means of which an incongruous, and therefore ludicrous idea is unexpectedly shot into the sentence. One or two examples will make the matter clearer than any definition. Two persons looking at a beggar-boy with an extraordinary big head-What a tower!' cried the first. What a tower!' cried the first. Say, rather,' replied the second, what a fort o' lice (fortalice).—A noted punster was once asked, with reference to Mr Carlyle's writings, if he did not like to expatiate in such a field. 'No,' was the felicitous rejoinder; I can't get over the style' (stile).-A Massachusetts lady complaining to. a friend that her husband (whose business had taken him to the far West) constantly sent her letters filled with expressions of endearment, but no money, was told, by way of comfort, that he was giving her a proof of his unremitting affection!

PUNCH, the chief character in a popular comic exhibition performed by means of Puppets (q. v.). Various accounts are given of the origin of the name. The exhibition is of Italian origin, and the Italian name is Pulcinella, or Policinella. According to one story, a peasant, a well-known character in the market-place of Naples, got the name Pulcinelli from dealing in fowls (pulcinelli), and after his death was personated in the puppet-shows of the San-Carlino theatre. Another account makes the word a corruption of Puccio d'Aniello, the

name of a witty buffoon of Acerra who joined a company of players and became the favourite of the Neapolitan populace. Others give his original name as Paolo Cinella. The variety and inconsistency of the legends shew them to be myths--histories invented to account for the name. The modern P. is only a modification of an ancient Mask (q. v.) to be seen represented on ancient vases, and taken perhaps from the Oscan Atellanæ; and the Italian name is pretty evidently a diminutive of pollice, the thumb-Tom Thumb (the dwarfs of northern mythology are sometimes styled däumling, thumkins). The English name Punch is apparently identical with Eng. paunch; Bavarian punzen, a cask; Ital. punzone, a puncheon; and denotes anything thick and short (e. g., a Suffolk punch). The name Punchinello seems to have arisen from blending the English and Italian names.

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 England 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 following is an outline of the plot as performed in 1813. Mr P., a gentleman of great personal attraction, is married to Mrs Judy, by whom he has a lovely daughter, but to whom no name is given in this piece, the infant being too young to be christened. In a fit of horrid and demoniac jealousy, P., like a second Zeluco, strangles his beauteous offspring. Just as he has completed his dreadful purpose, Mrs Judy enters, witnesses the brutal havoc, and exit screaming; she soon returns, however, armed with a bludgeon, and applies it to her husband's head, which to the wood returns a wooden sound.' P. at length exasperated seizes another bludgeon, soon vanquishes his alreadyweakened foe, and lays her prostrate at his feet; then seizing the murdered infant and the window into the street. The dead bodies having expiring mother, he flings them both out of the been found, police-officers enter the dwelling of P., who flies for his life, mounts his steed; and the author neglecting, like other great poets, P., who flies for his life, mounts his the confining unities of time and place, conveys his hero into Spain, where, however, he is arrested by an officer of the terrible Inquisition. enduring the most cruel tortures with incredible fortitude, P., by means of a golden key, opens his prison-door, and escapes. The conclusion of the is first overtaken by Weariness and Laziness in the story is satirical, allegorical, and poetical. The hero Disease, in the disguise of a physician, next arrests shape of a black dog, which he fights and conquers; him; but P. 'sees through the thin pretence,' and dismisses the doctor with a few derogatory kicks. Death at length visits the fugitive; but P. lays about his skeleton carcass so lustily, and makes the bones of his antagonist rattle so musically with a bastinado, that 'Death his death's blow then received.' Last of all comes the Devil; first under the appearance of a lovely female, but afterwards in his own natural shape, to drag the offender to the infernal regions, to expiate his dreadful crimes. Even this attempt fails, and P. is left triumphant over Doctors, Death, and the Devil. The curtain falls amid the shouts of the conqueror, who, on his victorious staff, lifts on high his vanquished foe.

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