Chap. 7.] Metallic Pumps. 221 CHAPTER VII. Metallic pumps-Of more extended application than those of wood- Description of one-Devices to prevent water in them from freezing-Wells being closed, no obstacle in raising water from them-Application of the atmospheric pump to draw water from great distances as well as depth-Singular circumstance attending the trial of a Spanish pump in Seville-Excitement produced by it-Water raised to great elevations by atmospheric pressure when mixed with air-Deceptions practised on this principle-Device to raise water fifty feet by atmospheric pressure-Modifications of the pump innumerable -Pumps with two pistons-French marine pump-Curved pump-Muschenbroeck's pump-Centrifugal pump-West's pump-Jorge's improvement-Original centrifugal pump-Ancient buckets figured in this chapter. THAT the public hydraulic machinery of the Romans was of the most durable materials sufficiently appears from Vitruvius. The chain of pots described by him was, contrary to the practice in Asia and Egypt, wholly of metal-the chain was of iron and the buckets of brass. The pumps of Ctesibius that were employed in raising water to supply some of the public fountains, he informs us, were also of brass and the pipes of copper or lead. Some of the oldest pumps extant in Europe are formed altogether of the latter. Leaden pumps were very common in the 16th century. They are mentioned by old physicians among the causes of certain diseases in families that drank water out of them. The pump of the celebrated alchymist, Dee, alluded to in the last chapter, was a leaden one; and which he expected to be able to transmute into gold, by means of the elixir or the philosopher's stone, which he spent his life and fortune in seeking. In the vicinity of some English lead mines such pumps have for many centuries been in use. The Italian pump that led to the discovery of atmospheric pressure was also a metallic one. The introduction of metals in the construction of pumps greatly extended their application and usefulness, for they were then no longer required to be placed directly over the liquids they raised. Those of wood were necessarily placed within the wells out of which they pumped water; but when the working cylinder and pipes were of copper or lead, the former might be in the interior of a building, while the reservoir or well from whence it drew water, was at a distance outside; the pipes forming an air-tight communication between them under the surface of the ground. The following figure, (No. 90) represents a common metallic sucking pump; the cylinder of cast-iron or copper, and the pipes of lead. It will serve to explain the operation of such machines in detail, and to show the extent of their application. When this pump is first used, water is poured into the cylinder to moisten the leather round the sucker, and the pieces which form the clacks or valves; it also prevents air from passing down between the sucker and the sides of the cylinder when the former is raised. Now the atmosphere rests equally on both orifices of the pipe, the open one in the well, and the other covered by a valve at the bottom of the cylinder: in other words, it presses equally on the water in the cylinder and in the well which covers both; but when by Not absolutely so, or in a strict philosophical sense, but the difference is so slight in an altitude of 25 or 28 feet, (the ordinary limits) as to be inappreciable in a practical point of view. 222 Common Pumps. [Book II. the depression of the handle or lever, the sucker is raised, this equality is destroyed, for the atmospheric column over the cylinder, and consequently d over the valve O is lifted up, and sustained by the sucker alone; it therefore no longer presses on the upper orifice, while its action on the lower one remains undiminished. Then as the external air cannot enter the pipe to restore the equilibrium except through its orifice immersed in the well; in its efforts to do so, (if the expression is allowable) it necessarily drives the water before it on every ascent of the sucker, until the air previously contained in the pipe is expelled, and both pipe and cylinder become filled with water. The subsequent operation is obvious. When the sucker descends, the clack on its upper surface is raised by the resistance of the water through which it passes; and when at the bottom of the cylinder, this clack closes by its own weight: so that when the sucker is again elevated, besides overcoming the resistance of the atmosphere, it carries up all the water above it, and which it discharges at the spout-at the same time the atmosphere resting undisturbed on the water in the well, pushes up a fresh portion into the vacuity formed in the cylinder, and the valve O prevents its return. No. 90. Common Metallic Pump. The horizontal distance between the cylinder or working part of the pump and the well is, in theory unlimited, but in practice it seldom exceeds one or two hundred feet. In all cases where long pipes are used, their bore should be enlarged in proportion to their length, or the velocity with which the sucker is raised, should be diminished; and for this reason-time is required to overcome the inertia and friction of long columns of water in pipes; hence a sucker should never be raised faster than the pipe can furnish water to fill the vacuity formed by its ascent. In pumps whose pipes have too small a bore, it frequently happens that the sucker is forcibly driven back when quickly raised, because the water had not time to rush through the pipe and fill the vacuity in the cylinder as rapidly as it was formed. The bore of wooden pumps being equal throughout, the water is not pinched or wire-drawn while passing through them, as in most of those of metal. This is one reason why they generally work easier than the latter. It is immaterial in what part of the pipe the valve O is: it is usually placed at the upper end for the convenience of getting to it when requiring repairs. When it fits close to its seat, the water always remains suspended in the pipe, (unless the latter should be defective) as mercury is sustained in a barometer tube. In cold climates it is a matter of some importance to prevent water in pumps from freezing. Metallic pumps are, from the superior conducting property of their material, more subject to this evil than those of wood. Of various devices a few may be mentioned. The old mode of enclosing Chap. 7.] Limits of the perpendicular length of Suction Pipes. 223 the pump in a case containing tanners' bark, charcoal, the dung of horses, &c. is continued. Others are to prevent the valve O from sitting close to its seat, or to open it, by pressing the sucker upon a pin attached to it, so that the contents of the cylinder and pipe may descend into the well; hence every time the pump is used a fresh portion is required to 'prime it.' A more common method is to connect the lower part of the cylinder with the suction pipe by a stop cock and short tube, as at C. By opening the cock the water in the pump descends through it into the pipe. But the usual practice in this country, is to make the cylinder of such a length that two or three feet of it may be below the surface of the ground, and out of the reach of the frost; about a foot above the valve O or lower box, a plain cock is inserted: in winter this cock is left partially open, and the water above escapes slowly through it into the ground; while that below, into which the sucker is made to extend at its lowest position, serves instead of fresh 'priming.' A similar device is attached to the lateral pipes that convey the water of the Schuylkill into the houses of Philadelphia. Some persons can scarcely conceive how the atmosphere can have access to a well, while the latter is covered with slabs of stone or timber, and a thick bed of clay or mould over all. They forget that it is the rarity of air, the extreme minuteness of its particles, which enables it to circulate through the finest soils, as freely as people pass through the various chambers and passages of their dwellings. Were the sides of a well coated, and its mouth covered with the best hydraulic cement—no sooner could the sucker or piston of a pump produce a partial vacuum within it, than the air would stream through the cement as water through a colander or shower bath. And if the top and sides were rendered perfectly air-tight, it would then enter the bottom and ascend through the water without any perceptible obstruction. If it were possible to make a well impervious to air, no water could be raised from it by one of these pumps: no movement of the sucker could then bring it up. We might examine the apparatus with solicitude-remove its defects with careconsult the learned with the Florentines, or get enraged like the Spanish pump maker of Seville;-still, the water, like Glendower's spirits of the deep, would in spite of all our efforts refuse to rise. When the atmospheric pump is required to raise water from a perpendicular depth, not exceeding 26 or 28 feet, (i. e. in those parts of the earth where the mercury in the barometer generally stands at 30 inches) the length of the cylinder need not exceed that which is required for the stroke of the sucker. In ALL cases, the perpendicular distance between the sucker, when at the highest point of its stroke and the level of the water, should never exceed the same number of feet as the tube of a barometer, at the place where the pump is to be used, contains inches of mercury. But in the temperate zones where pumps are chiefly used, the pressure of the air varies sometimes to the extent of two inches of mercury, or between two and three feet of water; hence the distance should be something less. And as the level of water in wells is subject to changes, it is the laudable practice of pump makers to construct the cylinder and rod of the sucker, of such a length, that the latter may always work within 26 or 28 feet of the water. By keeping the above rule in view, water may be raised by these pumps from wells of all depths; for after it has once entered the cylinder, it is raised thence by the sucker independently of the atmosphere, and to any height to which the cylinder is extended. This seems to have been well understood by old engineers., The remark of those who made 224 Singular incident in trying a Pump at Seville. [Book II. the Florentine pump is a proof; and others might be adduced from much older authorities. Plate 48, in Besson's Theatre, represents an atmospheric pump raising water from a river to the top of a high tower. The cylinder is square, formed of plank and bound with iron clamps. It is shown as nearly four times the length of the suction pipe, which is round. When pump rods are required of great length, they should be made of pine. This wood does not warp, and as it is rather lighter than water, its weight has not to be overcome (like iron rods) when raising the sucker. A circumstance to which we have slightly alluded, was announced in the public papers of Europe, in the year 1766, which roused the attention of philosophers; for it seemed to threaten a renewal of the disputes about a vacuum, and the ascent of water in pumps and siphons, &c. A tinman of Seville, in Spain, undertook to raise water from a well 60 feet deep, by the common pump. Instead of making the sucker play within 30 feet of the water, he made the rod so short, that it did not reach within 50 feet of it. As a necessary consequence, he could not raise any. Being greatly disappointed, he descended the well to examine the pipe, while a person above was employed in working the pump; and at last in a fit of despair, at his want of success, he dashed the hatchet or hammer in his hand, violently against the pipe. By this act a small opening was made in the pipe about ten feet above the water-when, what must have been his surprise! the water instantly ascended and was discharged at the spout! The fact being published, it was by some adduced as a proof that the pressure of the atmosphere could sustain a perpendicular column of water much longer than 32 or 34 feet, and consequently that the experiments of Torricelli and Pascal were inconclusive. M. Lecat, a surgeon at Rouen in Normandy, repeated the experiment with a pump in his garden: he bored a small hole in the suction pipe ten feet above the water, to which he adapted a cock. When it was open, the water could be discharged at the height of 55 feet, instead of 30 when it was shut. As might be supposed, these experiments when investigated, instead of overthrowing the received doctrine of atmospheric pressure, more fully confirmed it. It was ascertained that the air on entering the pipe became mixed with the water; and which therefore, instead of being carried up in an unbroken column, was raised in disjointed portions, or in the form of thick rain. This mixture being much lighter than water alone, a longer column of it could be supported by the atmosphere: and by proportioning the quantity of air admitted, a column of the compound fluid may be elevated one or two hundred feet by the atmospheric pump; but there is no advantage in raising water in this manner by the pump, and we believe it is seldom or never practiced. In a paper, on the duty performed by the Cornwall Steam Engines in raising water, in the Journal of the Franklin Institute for May, 1837, it is stated that a little air is sometimes admitted in the pump pipes, which it is alledged, "made the pump work more lively, in consequence of the spring it gave to the column of water, and caused less strain to the machinery." In the same paper Mr. Perkins states that forty years before, an attempt was made to impose upon him in this country, a pump which raised water by atmospheric pressure 100 feet: but he detected "a small pin hole" in the pipe through which the air was admitted. The same deception it seems gave rise to the humorous poetical satire, 'Terrible Tractoration.' The ingenious author states in his preface, that he was employed in 1801, as agent for a company in Vermont, and of which he was a member, to proceed to London, and secure a patent for Chap. 7.] Modifications of Atmospheric Pumps. 225 'a new invented hydraulic machine.' "I was urged to hurry my departure in consequence of a report in circulation, that certain persons by stealth had made themselves masters of the invention, and were determined to anticipate us in our object of securing a patent in London. In consequence of this report, the experiments made with this machine were performed in a hasty manner. By it, water was raised through leaky tin pipes in a hasty experiment, 42 feet from the surface of the fountain to the bottom of the cylinders, in which the pistons were worked. I embarked from New-York the 5th of May, and arrived in London after a tedious passage the 4th of July. I waited on Mr. King, then ambassador from the United States, to whom I had letters, and was by him favored with a letter to Mr. Nicholson, an eminent philosopher and chemist. With this gentleman I had several interviews on the subject of my hydraulic machine, and from him received an opinion in writing unfavorable to its merits. I likewise made a number of experiments in London, with a different result from what I had seen in Vermont. In this desperate situation of the adventure, I received a letter from one of the Vermont Company, informing me there was a deception in the patent-that from experiments made subsequent to my departure, it appeared that no water could be raised by Langdon's invention higher than by the common pump, unless by a perforation in the pipe, which made what the inventor called an air hole, and which by him had been kept a secret. Mr. Nicholson informed me that a similar deception had been practised on the Academicians of Paris, but that the trick was discovered by the hissing noise made by the air rushing into the aperture." From the disappointment Mr. Fessenden turned to his pen, and wrote The modern Philosopher or Terrible Tractoration.' See preface to 2nd American ed. Phil. 1806. It is possible however to raise water by a short cylinder, fifty or even a hundred feet high, but for all practical purposes the device is useless. The first thing of the kind that we know of, was accomplished nearly forty years ago by a boy. He fixed a small pump (the cylinder was 12 inches in length) in the garret of a high dwelling, and a tub of water in the cellar, the perpendicular distance being nearly 50 feet. About half way up the stairs, he placed a close vessel, (a three gallon tin boiler) from the bottom of which a small leaden tube was continued to the pump cylinder; and another tube being soldered to the top, descended into the tub of water. A third tube was soldered to the top of the vessel, and terminated near the pump, having a cock soldered to the end. This cock being shut and the pump worked, the air in the pipes and the vessel was withdrawn, and the latter consequently filled with water by the atmosphere; he then opened the cock which admitted the atmosphere to act on the surface of the water in the vessel, and by again working the pump the contents of the vessel were raised and discharged in the garret. By a series of close vessels placed at distances not exceeding 30 feet above each other, water may be raised in this manner to any elevation. It is impossible to notice here a moiety of the projects for improving the atmospheric pump and the various parts of which it is composed; their name is legion, and this volume is far too limited to comprise an account of them all. Those that we are about to describe are of modern date, but it does not therefore follow that they were unknown to the ancients. Men in every age, when striving to accomplish a specific object, naturally fall into similar trains of thought, and hit upon the same or nearly the same devices. Could the ancient history of this machine be procured, it would we have no doubt prove, that (like the instruments invented by a celebrated French surgeon, fac-similes of which of exquisite finish, were |