228

Muschenbroeck's Pump.

[Book II.

it formed a part, served as a fulcrum on which the rod and handle (both of one piece) moved. The rod was curved so as to move in the centre of the chamber.

No. 93. Curved Pump.

The objects supposed to have been attained by this arrangement, were "greater simplicity of workmanship," and "greater steadiness and precision of action" (of the sucker.) The device is ingenious, but can never be generally adopted. The spring of the rod with the wear of the bolt on which it turns, must soon render the play of the sucker and wear of the chamber unequal: the difficulty and expense of making the latter curvilinear, and of repairing it when bruised or otherwise injured, are fatal objections. The pipe must be separated from the chamber to get at the

lower box or valve; and the application of the pump is limited to depths within 30 feet. We have noticed it, lest the same idea occurring to some of our mechanics, should lead them to a useless expenditure of time and money. In the same year a patent was issued in England for making the cylinder in the form of a ring, or nearly so, the centre of which was the fulcrum on which the piston turned, and an alternating motion was imparted to the latter. Repertory of Arts, vol. xxxv. 1819.

An interesting modification of the atmospheric pump was described by Muschenbroeck in his Natural Philosophy. Instead of a piston or sucker working inside of the cylinder, the latter itself is moved, being made to slide over the pipe somewhat in the manner of telescope tubes. No. 94 represents this pump. The upper end of the suction pipe, being made of copper or brass, and its exterior smooth and straight, is passed through the bottom of a small cistern. Its orifice is closed by a valve opening upwards. A short cylinder whose diameter exceeds that of the suction pipe is slipped over the latter; and to its lower end a stuffing box is adapted to prevent air or water from passing between them. Its upper

Chap. 7.]

Centrifugal Pump.

end is covered by a valve also opening upward. The pump rod is attached to the same end by a fork, as represented in the figure. By moving the cylinder up and down, the air within it and the pipe is soon expelled, and its place occupied by a portion of the water in which the lower end of the suction pipe is immersed. When the cylinder is then raised the atmosphere forces up water into it, and when it is depressed, the water being prevented by the valve on the end of the pipe from descending into the well, escapes out of that on the top of the cylinder, precisely as in the bellows pump. (p. 206.) By keeping water in the cistern, air is effectually prevented from entering between the pipes at the stuffing box, even if it be not perfectly tight. A cup or dish formed on the upper end of the cylinder to contain a little water over, the valve, would be an advantage in this description of pumps, for any defects in it by which a vacuum could not then be air is admitted would be fatal, as formed within the cylinder, and of course no water raised by it. Our common pumps would be almost useless if water was not kept over the valves; it is that which renders them air tight, and consequently efficient. In the early part of the 18th century, a new method of exciting the sure of the atmosphere for the purpose of raising water was adopted. Its discoverer burst the fetters with which long established modes of accomplishing this object had embarrassed common minds. He left the old track entirely, and the result of his researches was a philosophical machine that bears no resemblance to those by which it was preceded.

pres

Most people are practically acquainted with the principle of the Centrifugal pump, viz. that by which a body revolving round a centre tends to recede from it, and with a force proportioned to its velocity: thus mud is thrown from the rims of carriage wheels, when they move rapidly over wet roads; a stone in a sling darts off the moment it is released; a bucket of water may be whirled like a stone in a sling and the contents retained even when the bottom is upwards. A sailor on ship board, or a housemaid, dries a wet mop by whirling it till the force communicated to the watery particles overcomes their adhesion to the woolen fibres. Boys sometimes stick pellets of tough clay to the end of a switch or flexible rod, and then drawing it quickly through the air, the force imparted to the balls

I

No. 95. Centrifugal Pump.

sends them to their destination. If a tube be substituted for the rod, and the end that is held in the hand closed, by a similar movement, balls dropped or water poured into it, would be thrown forward in like manner; and if by some arrangement the movement of the tube was made continuous, projected streams of either balls or water might be rendered constant: the centrifugal gun is a contrivance to accomplish the one-the centrifugal pump the other.

This pump generally consists of tubes, united in the form of a cross or letter T, placed perpendicularly in the water to be raised. (No. 95.) The lower end is supported on a pivot; perforations are made to admit the water, and just above them a valve to retain it when the pump is not in motion. The ends of the transverse part are bent downwards to dis

230

Centrifugal Pumps.

[Book II. charge the water into a circular trough, over which they turn. To charge it, the orifices may be closed by loosely inserting a cork into each, and then filling the pump through an opening at the top which is then closed by a screw cap. A rapid rotary motion is imparted to the machine by a pulley fixed on the axis and driven by a band, from a drum, &c. The centrifugal force thus communicated to the water in the arms or transverse tube, throws it out; and the atmosphere pushes up the perpendicular one fresh portions to supply the place of those ejected. These pumps are sometimes made with a single arm like the letter L inverted; at others quite a number radiate from the upright one. It has also been made of a series of tubes arranged round a vertical shaft in the form of an inverted cone. A valuable improvement was submitted by M. Jorge to the French Academy in 1816. It consists in imparting motion to the arms only, thus saving the power consumed in moving the upright tube, and by which the latter can be inclined as circumstances or locations may require.

A combination of the centrifugal pump with Parent's or Barker's mill, was proposed by Dr. West, which in some locations may be adopted with advantage. It is simply a vertical shaft round which two tubes are wound: (No. 96) the upper one is the pump; the lower one the mill. The area of the lower one should be to that of the upper in the inverse ratio of the perpendicular height, and as much more as is necessary to overcome the friction. The cup or basin into which the stream (part of which is to be raised) is directed, may be attached to the shaft and turn with it, or the latter may pass through it. Tilloch's Phil. Mag. vol. xi.

No. 96. West's Pump.

No. 97. Le Demour's Pump.

The first centrifugal pump appears to have been invented by M. Le Demour, who sent a description of it to the French Academy in 1732. (Machines approuvé. Tom. vi, p. 9.) It was merely a straight tube attached in an inclined position to a vertical axis, and whirled round by the handle the tube was fastened by ligatures to three strips of wood projecting from the axis, as shown at No. 97.

With this pump we close our remarks on devices for raising water by atmospheric pressure; more might have been added, but as nearly all the machines yet to be described illustrate the same principle, the reader is referred to the following Books, and particularly to the atmospheric and forcing pumps described in

the next one.

[The vessels under the pump spouts in Nos. 90, 93 and 94, are Roman bronze buckets from Pompeii.]

END OF THE SECOND BOOK,

BOOK III.

MACHINES FOR RAISING WATER BY COMPRESSURE INDEPENDENTLY OF ATMOSPHERIC INFLUENCE.

CHAPTER I.

DEFINITION of machines described in this Book-Forcing Pumps-Analogy between them and bellows -History of the bellows that of the pump-Forcing pumps are water bellows-The Bellows of antediluvian origin-Tubal Cain-Anacharsis-Vulcan in his forge-Egyptian, Hindoo, and Peruvian blowing tubes-Primitive bellows of goldsmiths in Barbary-Similar instruments employed to eject liquids-Devices to obtain a continuous blast-Double bellows of the Foulah blacksmiths, without valves-Simple Asiatic bellows-Domestic bellows of modern Egypt-Double bellows of the ancient Egyptians-Bellows blowers in the middle ages-Lantern bellows common over all the East-Specimens from Agricola -Used by negroes in the interior of Africa-Modern Egyptian blacksmiths' bellows-Vulcan's bellows -Various kinds of Roman bellows-Bellows of Grecian blacksmiths referred to in a prediction of the Delphic oracle-Application of lantern bellows as forcing pumps-Sucking and forcing bellows pumps -Modern domestic bellows of ancient origin-Used to raise water-Common blacksmiths' bellows employed as forcing pumps-Ventilation of mines.

MACHINES of the third class described in this Book, are such as act by compressure: the water is first admitted into close vessels and then forcibly expelled through apertures made for that purpose. This is effected in some by compressing the vessels themselves, as in bellows pumps-in others by a solid body impinging on the surface of the liquid, as in fire engines-sometimes a column of water is used for the same purpose, at others the expansive force of compressed air. Of the last two, Heron's fountain, air engines, and soda fountains, are examples. Strictly considered, these machines have nothing to do with the pressure of the atmosphere, (the active principle of those of the second class,) but in practice it is very generally employed. When the working cylinder of a forcing pump is immersed in the water it is intended to raise, or when the latter flows into it by gravity, it is a forcing pump simply; but when the cylinder is elevated above the water that supplies it, and consequently is then charged by atmospheric pressure, the machine is a compound one, embracing the peculiar properties of both sucking and forcing pumps. The latter therefore differ from the former in raising water above their cylinders; and to elevations that are only limited by the strength of their materials and the power employed to work them. They have been considered by some writers as the oldest of all pumps. We shall consider their varieties in the order in which we suppose they were developed.

An intimate connection has ever subsisted between the forcing pump and the bellows; they are not only identical in principle, but every form adopted in one has been applied to the other. The bellows, from the simple sack or skin employed by the negroes of Africa to the complex and efficient instrument of China, and the enormous blowing machines of

232

Antiquity of Bellows.

[Book III. our foundries, has been used to raise water: and every modification of the pump, not even excepting the screw, has been applied as a bellows. A singular proof of the analogy between them and of their connection in ancient times, is, that in one of the earliest accounts we have of the cylindrical pump, (viz. by Vitruvius) it was used as a bellows "to supply wind to hydraulic organs." And that rotary pumps are as numerous as rotary bellows, is known to every mechanic. Thus, while pumps have been used as bellows, bellows have been employed as pumps; and every device to obtain a continuous current of air in the one, has been adopted to induce an unbroken stream of water in the other.

The history of the bellows is also that of the pump; and if we mistake not it affords the only legitimate source now open in which the origin of the latter can be sought for with any prospect of success. Under this impression we shall examine the bellows of various people, and in doing so the reader will find an auxiliary, but very important branch of the subject, illustrated at the same time, viz. that which relates to VALVES, for the bellows was probably the first instrument of which they formed a part. No other machine equally ancient can be pointed out in which they were required. In fine, the forcing pump is obviously derived from the bel lows, or rather it is an application of that instrument to blow water instead of air-an application probably coeval with its invention.

The origin of the arts is generally considered as a subject of mere conjecture. Antiquarians and historians despair of discovering any thing of importance relating to the early history of any of the simple machines. In the present case, however, there can be no doubt that the first bellows was the mouth; and it was the first pump too, both atmospheric and forcing. The representation of it when employed as a bellows was a favorite subject with ancient statuaries and painters. Pliny gives several examples, and among others, Stipax the Cyprian, who cast an elegant figure of a boy "roasting and frying meat at the fire, puffing and blowing thereat with his mouth full of wind, to make it burn." Aristoclides, was also celebrated for a painting of a boy, "blowing hard at the coals; the whole interior of the room appeared to be illuminated with the fire thus urged by the boy's breath, and also what a mouth the boy makes." Holland's Translation.

That the bellows is of antediluvian origin, there can be little doubt, for neither Tubal Cain nor any of his pupils could have reduced and wrought iron without it. The tongs, anvil and hammer of Vulcan, (or Tubal Cain) have come down to our times, and although the particular form of his bellows be not ascertained, that instrument is, we believe, as certainly continued in use at the present day, as the tools just named. Nor is there any thing incredible in such belief, for if even the common opinion, that the whole globe was enveloped in the deluge, be true, Noah and his sons, aware that the destinies of their posterity, so far as regarded the arts of civilization, must in a great measure depend upon them, would naturally secure the means of transmitting to them the knowledge of those machines that related to metallurgy, as among the most essential of all. Of these, the bellows was quite as important as any other; without it, other tools would have been of little avail. Now if we refer to oriental machinery, (among which the bellows of the son of Lamech is to be found if at all,) we shall find, in accordance with its characteristic unchangeableness, that the instrument now used over all Hindostan and Asia in general, and by the modern blacksmiths of Cairo and Rosetta, is identical with

a Hachette's Traité élémentaire des Machines, p. 142.