Chap. 4.]

Double acting Pump.

271

CHAPTER IV.

FORCING pumps continued: La Hire's double acting pump-Plunger pump: Invented by Moreland; the most valuable of modern improvements on the pump-Application of it to other purposes than raising water-Frictionless plunger pump-Quicksilver pumps-Application of the principle of Bramah's press by bees in forcing honey into their cells. Forcing pumps with hollow pistons: Employed in French water-works-Specimen from the works at Notre Dame-Lifting pump from Agricola-Modern lifting pumps-Extract from an old pump-maker's circular-Lifting pumps with two pistons--Combination of hollow and solid pistons-Trevethick's pump-Perkins' pump.

Or the various modifications which the forcing pump has undergone in recent times we can notice but a few, and of these the greater part were most likely known to ancient engineers. The most prominent one is that by which the machine is made double acting. Now the device by which this is effected has not only frequently occurred to quite a number of ingenious men in their endeavours to improve the pump who were ignorant of its having been accomplished; but it is an exact copy of one that has been applied to the wind pump of China from time immemorial, (see No. 112;) it probably therefore did not escape such men as Ctesibius, and Heron, and others who appear to have exercised their ingenuity and sagacity to the utmost in order to improve this machine, and who were enthusiastically attached to such researches. The remarks on modern improvements of the atmospheric pump, pages 225-6, are equally applicable to those of the forcing one; and it is worthy of remark, that notwithstanding the present improved state of mechanical science, the ancient forms of both now prevail-for the forcing pump as made by Ctesibius in Egypt, and as described by Vitruvius as used by the Romans, is still more common than any other.

The double acting pump represented in the figure, was devised by M. La Hire in the early part of the last century. His description of it was published in the Memoirs of the French Academy in 1716; and from one of his expressions we perceive (what was indeed very natural) that if he was not indebted for the improvement to the contemplation of bellows, these instruments were at least closely associated with it in his mind. The pump I propose [he observes] furnishes water continually, "just as the double bellows makes a continual wind." The piston rod passes through a stuffing box or collar of leathers on the top of the cylinder. The latter has four openings covered by valves or clacks; two for the admission of water and the same number for its discharge. A B is the suction pipe, and C D the ascending or discharging one. Suppose the lower end of the suction pipe in water; then if the piston be thrust down, the valve near B will close, and the air in the lower part of the cylinder will be forced through the valve at D and up the pipe D C, and in consequence of the rarefaction of the air above the piston, the valve at C will be

272

Plunger Pump,

[Book III. closed, and water will ascend through B A and enter the cylinder at A; then if the piston be raised it will force all the water above it through the valve at C, the only passage for it, while at the same time a fresh portion will enter the cylinder through the valve at B. Thus at every stroke of the piston, whether up or down, the contents of the cylinder are forced out at one end, and it is replenished at the same time through the other; this pump therefore discharges double the quantity of water that an ordinary one of the same dimensions does. The piston rod may be inserted through either end of the cylinder, as circumstances may require. These pumps are frequently used in a horizontal position.

Another variation of the forcing pump consists in making the piston of the same length as the cylinder but rather less in diameter, so that it may be moved freely in the former without touching the sides. These pistons are made wholly of metal and turned smooth and cylindrical, so as to work through a stuffing box or cupped leathers. The quantity of water raised at each stroke has therefore no reference to the capacity of the cylinder, however large that part of one of these pumps may be, for the liquid displaced by the piston can only be equal to that part of the latter that enters the cylinder. Switzer has given a figure and description of an old engine composed of three of these pumps "that has been some years erected in the county of Surrey." Newton has figured the piston bellows described by Vitruvius as furnishing wind to hydraulic organs in a similar way. In Commandine's translation of Heron's Spiritalia, page 159, the same kind of plunger is figured in a pump belonging to a water organ; and at p. 71, a fire-engine, with two working cylinders, has pistons of the same kind. These pistons were formerly named plungers, and the pumps plunger-pumps. Their construction and action will be understood by the

figure, which represents one of a number that were employed in the water-works, York Buildings, London, in the last century. The piston was of brass, cast hollow and filled with lead, the outside being "turned true and smooth." A short rod attached to the upper end of the piston was connected by a chain to the arched end of a vibrating beam, that was moved by one of Newcomen's engines. The piston was therefore merely raised by the engine, while its own weight carried it down to render it sufficiently heavy for this purpose, a number of leaden disks (or cheeses, as they were named from their form) having holes in their centres, were slipped over the rod and rested upon the piston, as in the figure. These were increased until they were found sufficient to press down the piston and force the water up the ascending pipe. The cupped leathers through which the piston worked, were similar to those now used in the hydrostatic press. A small cistern was sometimes formed on the top of the pump, that the water it contained might prevent air from entering through the stuffing box or between the cupped leathers: it served also to charge the pump through a small pipe or cock. A valve opening upwards was sometimes placed just above the plug of the cock, and the latter left open when the machine was started, that the air within the cylinder might escape; and as soon as the water rose and filled the pump, the cock was shut. It is immaterial at what part of the cylinder the forcing or ascend

Chap. 4.]

Invented by Moreland.

273

ing pipe is attached, whether at the bottom, near the top, or at any intermediate place. Small pumps of this kind are now commonly employed to feed steam boilers and for other purposes, and are worked by levers like the ordinary lifting and forcing pumps, the pistons being preserved in a perpendicular position by slings, &c.

66

These pumps are believed to be of English origin, having been invented by Sir Samuel Moreland, master of mechanics" to Charles 2d. Like some old philosophers, he exercised his ingenuity in improving hydraulic and other engines, for raising water. Besides the plunger pump, for which he obtained a patent in 1675, he invented a "cyclo-elliptic movement" for transmitting motion to piston rods, a figure of which is inserted by Belidor in the second volume of his Arch. Hydraulique. He is also the reputed inventor of the speaking trumpet,a of a capstan, and a steam-engine. In 1681 he made experiments with an engine consisting of two or more of his pumps at Windsor, in presence of the king and court, during which he forced water from the Thames in a continual stream to the top of the castle; and according to Dr. Hutton, " sixty feet higher." Moreland visited France the same or the following year, by order of the king, to examine the famous water-works at Marli, and while in Paris he exhibited models of his pump before the French court, and also constructed several for his friends. In 1683 he presented an account of various machines for raising water to Louis 14th, in a manuscript volume written and ornamented with much elegance; and in 1685, an account of his improvements was published in Paris in a work entitled, "Elévation des eaux par toute sorte de machines, réduite à la mesure, au poids, à la balance, par le moyen d'un nouveau piston et corps de pompe; et d'un nouveau mouvement cyclo-elliptique, et rejetant l'usage de toute sorte de manivelle ordinaires, par le Chevalier Moreland." It does not appear that he ever published this work in England, for Switzer had recourse to Ozanam, a French writer, for a description of Moreland's pump; as he could procure no English account of it, "having taken great pains to find out what Sir Samuel had left on that head to no purpose." Ozanam states that Moreland spent "twelve years study and a great deal of money" to bring this pump to perfection; "and without this new invention it would have been impossible to have reduced the raising of water to weight and measure, as he has done." The latter observation refers to the leaden weights placed on the piston rod, and the quantity of water raised by them: the water and the elevation to which it was raised being compared with the sum of the weights employed to force it up.b

If we mistake not this is the most valuable and original modification of the forcing pump that modern times have produced. The friction of the piston is not only greatly reduced, but the boring of the cylinder is dispensed with; an operation of considerable expense and difficulty, particularly so, before efficient apparatus for that purpose was devised. Another advantage is the facility of tightening the packing without taking out the piston or even stopping the pump. The value of Moreland's invention in

a There is an instrument very like a speaking trumpet in the hands of a figure in one of the illustrations of the Eneid, executed in the fourth or fifth century, in the 25th plate of "Painting" in D'Agincourt's History of the Fine Arts. It is a conical tube, the length being equal to that of the individual using it; and by which he appears to direct, from the top of a tower, the combatants below. Kircher has given a figure of a trumpet through which he supposed Alexander spoke to his army.

See Switzer's Hydrostatics, plate 25, pp. 302, 357. La Motraye's Travels, vol. iii, Lon. 1732. Desaguliers' Philos. vol. ii, 266. Belidor's Architecture Hydraulique, tom. ii, 61, and L'Art D'Exploiter Les Mines, in Arts et Metiers, page 1058, and planche 47.

274

Frictionless Plunger Pump.

[Book III. the estimation of engineers appears from the increasing employment of it. It is, moreover, for aught that is known to the contrary, the parent of the common lifting pump; and to its inventor the double acting steamengine of Watt is in some measure due, the efficiency of that noble machine depending entirely upon closing the top of the cylinder and passing the piston rod through a stuffing box-both of which had already been done in this pump. Steam-engines have also been constructed on the same plan as these pumps; one long piston playing in two horizontal cylinders, and the power transmitted from it by means of a cross-head attached to the middle of its length, and on that part which moves between the stuffing boxes. Another celebrated machine is also copied from them -Bramah's hydrostatic press is one of Moreland's pumps.

There is another species of plunger pumps in which the stuffing box is dispensed with, and consequently the piston works without friction. A

J

square wooden tube, or a common pump log of sufficient length, and with a valve at its lower end is fixed in the well as shown in the figure. The depth of the water must be equal to the distance from its surface to the place of delivery; and a discharging pipe having a valve opening upwards is united to the pump tree at the surface of the water in the well. The piston (a solid piece of wood) is suspended by a chain from a working beam, and loaded sufficiently with weights to make it sink. As the liquid enters the pump through the lower valve, and stands at the same level within as without, whenever the piston descends, it necessarily displaces the water, which has no other passage to escape but through the discharging pipe, in consequence of the lower valve closing. And when the piston is again raised as in the figure, a fresh portion of water enters the pump and is driven up in like manner.

Dr. Robison observes that he has seen a machine consisting of two of these pumps, made by an untaught laboring man. The plungers were suspended from the ends of a long beam, on the upper surface of which the man walked, as on the picotah of India. He stood on one end till one plunger descended to the bottom of its tube, and he then walked to the other end, the declivity at first being about 250, but gradually growing less as he advanced. In this way he caused the other plunger to descend, and so on alternately.

No. 124. Frictionless Plunger
Pump.

By this machine a feeble old man whose weight was 110lbs. raised 7 cubic feet of water 11 feet high in a minute, and wrought eight or ten hours every day. A stout young man weighing 134lbs. raised 8 cubic feet to the same height in the same time. The application of this pump is extremely limited, and there is a waste of power in the water that is uselessly raised around the piston at every stroke.

The pistons of preceding machines are made of solid materials; but the pump now to be described has a liquid one. It was invented about the year 1720, by Mr. Joshua Haskins, who made the first experiment with it in the house and presence of the celebrated Desaguliers. His design

Chap. 4.]

Mercurial Pump.

275

was to avoid the friction and consequent loss of power in common pumps, he therefore "contrived a new way of raising water without any friction of solids; making use of quicksilver instead of leather, to keep the air or water from slipping by the sides of the pistons." Various modifications of it were soon devised by the inventor, by Dr. Desaguliers, and by Mr. William Vreem, the assistant of the latter, "who was an excellent mechanic." One form of it is represented by the figure. A is the suction pipe, the lower end of which is inserted in the water to be raised. Its upper end terminates in the chamber C, and is covered by a valve. The forcing pipe B, with a valve at its lower end, is also connected to the chamber.

Between these valves a pipe, open at both ends, is inserted and bent down, as in the figure. The straight part attached to it is the working cylinder of the pump and should be made of iron. Another iron pipe, a little larger in the bore than the last, and of the same length, is made to slide easily over it. This pipe is closed at the bottom and suspended by chains or cords, by which it is moved up and down. Suppose this pipe in the position represented, and filled with mercury-if it were then lowered, the air in the cylinder and between the valves would become rarified, and the atmosphere pressing on the surface of the water in which the end of A is placed, would force the liquid up A till the density of the contained air was the same as before; then by raising the pipe containing the mercury, the air, unable to escape through the lower valve, would be forced through the upper one; and by repeating the operation, water would at last rise and be expelled in the same way; provided the elevation to which it is to be raised does not exceed thirteen times the depth of the mercurial column around the cylinder; the specific gravity of quicksilver being so many times greater than that of water. When the depth of the former is 30 inches, the latter may be raised as many feet in the suction pipe and forced up an equal distance through the forcing one, making together an elevation of sixty feet; but if water be required higher, the depth of the mercurial column in the moveable pipe must be proportinably increased. To make a small quantity of mercury answer the purpose, a solid piece of wood or iron that is a little less than the cylinder, is secured to the bottom of the moveable vessel as shown in the centre: this answers the same object as an equal bulk of mercury.

These pumps have their disadvantages: they are expensive; and however well made, the quantity of quicksilver required is considerable-the agitation consequent on the necessary movement soon converts it into an oxide and renders it useless-great care is also required in working these machines; if the movements are not slow and regular, the mercury is very apt to be thrown out; to prevent which the upper end of the vessel con taining it is dished or enlarged. For experimental researches modifications of such pumps may be useful, but for the reasons above stated, they have never been extensively employed in the arts. A simple form of one is described in a late volume of the London Mechanics' Magazine, and also in the 22d vol. of the Journal of the Franklin Institute, p. 327. See