Chap. 1.]

Water-Ram.

371

operation is continued, as long as the spring affords a sufficient supply and the apparatus remains in order.

The surface of the water in the spring or source should always be kept at the same elevation, so that its pressure against the valve E may always be uniform-otherwise the weight of E would have to be altered as the surface of the spring rose and fell.

This beautiful machine may be adapted to numerous locations in every country. When the perpendicular fall from the spring to the valve E is but a few feet, and the water is required to be raised to a considerable height through F, then, the length of the ram or pipe B, must be increased, and to such an extent that the water in it is not forced back into the spring when E closes, which will always be the case if B is not of sufficient length. Mr. Millington, who erected several in England, justly observes that a very insignificant pressing column is capable of raising a very high ascending one, so that a sufficient fall of water may be obtained in almost every running brook, by damming the upper end to produce the reservoir, and carrying the pipe down the natural channel of the stream until a sufficient fall is obtained. In this way a ram has been made to raise one hundred hogsheads of water in twenty-four hours to a perpendicular height of one hundred and thirty-four feet, by a fall of only four feet and a half. M. Fischer of Schaffhausen, constructed a water-ram in the form of a beautiful antique altar, nearly in the style of that of Esculapius, as represented in various engravings. A basin about six inches in depth, and from eighteen to twenty inches in diameter, received the water that formed the motive column. This water flowed through pipes three inches in diameter that descended in a spiral form into the base of the altar; on the valve opening a third of the water escaped, and the rest was forced up to a castle several hundred feet above the level of the Rhine.

A long tube laid along the edge of a rapid river, as the Niagara above the falls, or the Mississippi, might thus be used instead of pumps, water wheels, steam-engines and horses, to raise the water over the highest banks and supply inland towns, however elevated their location might be; and there is scarcely a farmer in the land but who might, in the absence of other sources, furnish his dwelling and barns with water in the same way, from a brook, creek, rivulet or pond.

If a ram of large dimensions, and made like No. 168, be used to raise water to a great elevation, it would be subject to an inconvenience that would soon destroy the beneficial effect of the air chamber. When speaking of the air vessels of fire-engines, in the third book, we observed that if air be subjected to great pressure in contact with water, it in time becomes incorporated with or absorbed by the latter. As might be supposed, the same thing occurs in water-rams; as these when used are incessantly at work both day and night. To remedy this, Montgolfier ingeniously adapted a very small valve (opening inwards) to the pipe beneath the air chamber, and which was opened and shut by the ordinary action of the machine. Thus, when the flow of the water through B is suddenly stopped by the valve E, a partial vacuum is produced immediately below the air chamber by the recoil of the water, at which instant the small valve opens and a portion of air enters and supplies that which the water absorbs. Sometimes this snifting valve, as it has been named, is adapted to another chamber immediately below that which forms the reservoir of air, as at B in No. 169. In small rams a sufficient supply is found to enter at the valve E.

Although air chambers or vessels are not, strictly speaking, constituent elements of water-rams, they are indispensable to the permanent operation

372

Canne Hydraulique

[Book IV. of these machines. Without them, the pipes would soon be ruptured by the violent concussion consequent on the sudden stoppage of the efflux of the motive column. They perform a similar part to that of the bags of wool, &c. which the ancients, when besieged, interposed between their walls and the battering rams of the besiegers, in order to break the force of the blows.

The ram has also been used in a few cases to raise water by atmospheric pressure from a lower level, so as to discharge it at the same level with the motive column or even higher. See Siphon Ram, in next book. The device by which Montgolfier made the ram self-acting, is one of the neatest imaginable. It is unique: there never was any thing like it in practical hydraulics, or in the whole range of the arts; and its simplicity is equal to its novelty, and useful effects. Perhaps it may be said that he only added a valve to Whitehurst's machine: be it so-but that simple valve instantly changed, as by magic, the whole character of the apparatus-like the mere change of the cap, which transformed the Leech Hakim into Saladin. And the emotions of Coeur de Lion, upon finding

great adversary had been his physician in disguise, were not more exquisite than those, which an admirer of this department of philosophy experiences, when he contemplates for the first time the metamorphosis of the English machine by the French Savan. The name of Montgolfier will justly be associated with this admirable machine in future ages. When all political and ecclesiastical crusaders are forgotten, and the memories of all who have hewed a passage to notoriety merely by the sword, will be detested-the name of its inventor will be embalmed in the recollections of an admiring posterity.

The water cane, or canne hydraulique, raises water in a different manner from any apparatus yet described. A modification of it in miniature has long been employed in the lecture descriptions of hydraulic machines. It

room, but it is seldom met with in is represented at No. 170; and consists of a vertical tube, in outward appearance like a walking cane, having a valve opening upwards at the bottom, and placed in the liquid to be raised. Suppose the lower end twelve or fifteen inches below the surface, the water of course would enter through the valve and stand at the same height within as without now if the tube were raised quickly, but not entirely out of the water, the valve would close and the liquid within would be carried up with it; and if, when the tube was at the highest point of the stroke, its motion was suddenly reversed (by jerking it back) the liquid column within would still continue to ascend until the momentum imparted to it at the first was expended; hence a vacuity would be left in the lower part of the instrument into which a fresh portion of water would enter, and by repeating the operation the

No. 170 No. 171

No. 172.

Walter Scott's Tales of the Crusaders.

Chap. 1.1

And its Modifications.

373

tube would become filled, and a jet of water would then be thrown from the upper orifice at every stroke. This effect obviously depends upon the rapidity with which the instrument is worked, i. e. a sufficient velocity must be given to the water by the upward stroke to prevent it descending, till the tube again reaches the lowest point, and consequently receives another supply of water. The instrument should be straight and the bore smooth and uniform, that the liquid may glide through with the least possible obstruction. As its length must be equal to the elevation to which the water is to be raised, it is necessarily of limited application, and especially so since the whole (both water and apparatus) has to be lifted at every stroke-not merely the liquid that is discharged, but the whole contents of the machine.

By making the upper part of the tube slide within another that is fixed, a short part only of the apparatus might then be moved, and by connecting an air chamber as in No. 171, a continual stream from the discharging orifice might be produced. A stuffing box should be adapted to the end of the fixed tube. Hachette suggested the application of a spring pole (like those used in old lathes) to communicate the quick reciprocating motion which these machines require.

No. 172 represents another form of the instrument. Two spiral tubes coiled round in opposite directions are secured to and moved by a vertical shaft. Their upper ends are united and terminate in one discharging orifice; the lower ones are enlarged, and each has a valve or clack opening inwards to retain the water that enters. By means of the handle A, which is mortised to the shaft, an alternating circular motion is imparted to the whole, and the water thereby raised through these coiled tubes on precisely the same principle as through the perpendicular ones just described. Thus, when the handle is moved either to the right hand or to the left, one valve closes, and the water within receives an impulse that continues its motion along the tube after the movement of the latter is reversed; and by the time its momentum is expended a fresh portion of water has entered that prevents its return. In this manner all the coils become filled, and then every additional supply that enters below drives before it an equal portion from the orifice above. This machine, therefore differs from Nos. 170 and 171 only, in being adapted to a horizontal instead of a perpendicular movement. Each tube in the figure forms a distinct machine, and should be considered without reference to the other. Their discharging orifices are united to show how a constant jet may be produced. By making the upper part turn in a stuffing box in the bottom of a fixed tube, as in No. 171, water might then be raised higher than the movable part of the apparatus.

That property by which all bodies tend to continue either in a state of rest or motion, viz: inertia, increases the effect of these machines, for when the momentum imparted to the liquid in the tubes is exhausted, inertia alone prevents it from instantaneously flowing back, and hence there is time for an additional portion of water to enter at the valve. The action of the canne hydraulique is similar to that by which persons throw water to a distance from a bucket, or a wash-basin. The momentum given to these vessels and their contents carries the latter to a distance, while the former are held back or retained in the hands. Coals are thus thrown from a scuttle, earth from a shovel, and it is the same when a traveler on a galloping horse, or when drawn furiously in an open carriage, continues on his journey after the animal suddenly stops-his adhesion to his seat, not being sufficient to resist the motal inertia of his body.

374

Machines for Raising Water by Fire.

[Book IV.

CHAPTER II.

Machines for raising water by fire: Air machines-Ancient weather-glasses-Dilatation of air by beat and condensation by cold-Ancient Egyptian air-machines-Statue of Memnon-Statues of Serapis and the Bird of Memnon--Decaus' and Kircher's machinery to account for the sounds of the Theban IdolRemarks on the Statue of Memnon-Machine for raising water by the sun's heat, from Heron-Similar machines in the sixteenth century-Air-machines by Porta and Decaus-Distilling by the sun's heat- Musical air machines by Drebble and Decaus-Air machines acted on by ordinary fire-Modifications of them employed in ancient altars-Bronze altars-Tricks performed by the heathen priests with fire-Others by heated air and vapor-Bellows employed in ancient altars-Tricks performed at altars mentioned by Heron-Altar that feeds itself with flame, from Heron-Ingenuity displayed by ancient priests-Secrets of the temples-The Spiritalia-Sketch of its contents-Curious Lustral Vase.

A separate book might with propriety have been devoted to machines which raise water through tubes by means of the weight, pressure, momentum, or other natural properties of liquids, without the necessary intervention of wheels, cranks, levers, &c. With such, those now to be described might also have been classed, since they too require neither external machinery nor force. They differ however from pressureengines and water-rams, and every other device yet noticed, in bringing into action a new element, viz. heat or fire. It is by this that the force upon which their movements depend is generated, viz. in the expansion of elastic fluids. There are two kinds of these machines which differ according to the fluid medium upon which the fire is made to act. In some this is common air, in others steam or vapor of water, and sometimes both steam and air have been employed. The present chapter is appropriated to air machines. These might be divided into two classes, according to the nature of the heat employed; in some this is derived from the sun; in others, from ordinary fire. Those in each class might also be arranged according to that property of the air upon which their action depends, viz. 1. the force developed by its expansion; 2. the vacuum formed by its condensation; 3. those in which both are combined. The first might be compared to forcing pumps, the second to sucking or atmospheric ones, and the third to those which both suck and force up the water.

It was observed in the second book (page 176) that all gases or airs are expanded by heat and contracted by cold. A proof of this is afforded by the usual mode of employing cupping-glasses; a minute piece of cotton or sponge dipped in alcohol is inflamed and placed in a glass; upon which the air becomes dilated or increased in bulk, so that a great part is driven out to make room for the rest; the mouth of the instrument is then applied to the place from which blood is to be withdrawn; the flame of the cotton is thereby extinguished and as the remaining air becomes cool it cannot resume its previous state of density, and consequently a vacuity or void is left in the glass. Plumbers sometimes make small square boxes of sheet lead; and on soldering in the covers the temperature of the contained air is so greatly increased, that before the soldering is completed a large portion is expelled, and when the boxes become cool every side is found slightly collapsed. This result is the required proof of the ves

Chap. 2.]

Dilatability of Air by Heat.

375

sels being tight. Now it is clear that if a communication was opened by a tube between the interior of one of these boxes and a vessel of water placed a few feet below, that the liquid would be forced into it (by the atmosphere) until the contained air occupied no greater space than it did before any part was driven out by the heat. This mode of raising liquids may be illustrated at the tea-table: Let a saucer be half filled with cold water, hold an inverted cup just over it and apply for a moment a small slip of lighted paper to the interior of the cup, drop the paper on the water and cover it with the cup, when the liquid contents of the saucer will be instantly forced up into the inverted vessel.

If an inverted glass siphon be partly filled with water and the orifice of one leg be then closed and that leg be held to the fire, the air expanding will drive out the liquid and cause it to ascend in the other leg. Several philosophical instruments illustrate the same thing. Previous to the discovery of atmospheric pressure and the invention of the barometer, the expansion of air by heat was the principle upon which the ancient weather glasses were constructed. They were made in great variety. The simplest consisted of a glass tube having a bulb blown on the closed end. It was held over a fire to dilate the air, and the open end was then plunged into a vessel of water. Its construction was the same as the modern barometer. Variations in the temperature and density of the atmosphere caused the water to rise and fall in the tube, as the contained air was dilated and contracted, and thus changes in the weather were indicated. From these instruments the barometer received its former name of "the weather glass."a

The degree of elevation to which water can be thus raised depends upon the temperature to which the contained air is subjected; its dilatation or increase of bulk being, according to some authors, in common with

a The following extract from a book published ten years before the discovery of atmospheric pressure, may interest some readers. Although the instruments to which it refers are no longer in use, they ought not to be entirely forgotten.

"A weather-glasse is a structure of at the least two glasses [a tube and the vessel containing the water] sometimes of three, foure, or more as occasion serveth, inclosing a quantity of water, and a porcion of ayer proporcionable; by whose condensacion or rarifaction the included water is subject unto a continual mocion, either upward or downward; by which mocion of the water is commonly foreshown, the state, change, and alteracion of the weather;-for I speak no more than what my own experience hath made me bold to affirm; you may (the time of the year, and the following observacions understandingly considered) bee able certainly to foretell the alteracion or uncertainty of the weather a good many hours before it come to pass.

There are divers severall fashions of weather-glasses, but principally two. 1. The circular glasse. 2. The perpendicular glasse. The perpendiculars are either single, double or treble. The single perpendiculars are of two sorts, either fixt or moveable: The fixt are of contrary qualities; either such whose included water doth move upward with cold, and downward with heat, or else upward with heat and downward with cold. In the double and treble perpendiculars, as the water ascendeth in one, it descendeth as much or more in the other. In the moveable perpendiculars, the glasse being artificially hanged, it moveth up and down with the water."

The author then describes the various kinds mentioned and tells his reader" if you doe well observe the form of the figures you cannot go amisse." He also gives directions for making coloured water for the tubes, such as " may be both an ornament to the work and delectable to the eye." Treatise on Art and Nature, A. D. 1633 or 4. See account of this book page 321. A modification of an air-glass may be found in the Forcible Movements of Decaus, (plate viii,) which he names an Engine that shall move of itself. Lord Bacon, in whose time these air glasses were common, presented what appears to have been an improved one and of his own invention, to the Earl of Essex, who it is said, was so captivated with it that he presented the donor with Twickenham Park and its garden, as a place for his studies. The instrument was named A secret curiosity of nature, whereby to know the season of every hour of the year, by a Philosophical Glass, placed (with a small proportion of water) in a chamber. An account of Lord Bacon's Works, London, 1679.