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Origin of obtaining a Vacuum by Currents of Steam. [Book V. draw the vapor arising from a surface of seven square feet. It would be an advantage to apply two or perhaps three separate blowing tubes, of different sizes, to each sugar pan-using the largest first, to draw off the the bulk of the vapor, and finishing with the smaller ones. There would be a saving of steam, and the vacuum might be carried higher towards the close of an operation with a very small tube and current.

Another mode of using these tubes to promote evaporation, is to draw air through liquids instead of forcing it through them with pumps, as in the pneumatic processes of concentrating sirups. An open boiler, four feet in diameter, was inverted and placed in another over a fire and containing sirup a blowing tube, the orifice of whose vacuum pipe was three-fourths of an inch diameter, was connected to the inverted vessel, and it drew so much air under the edges as to cool the liquid to such a degree that the operation of concentration was prolonged to twice the ordinary time.

While engaged in making the experiments described in this chapter, (in 1835) and stimulated by the conviction that we were the first thus to apply currents of steam for the purposes of raising water and promoting the evaporation of liquids at low temperatures, &c. we were exceedingly surprised to learn that something of the kind had been previously done, or proposed to be done, in France. As we had made preparations to secure the invention by a patent here, and by others in Europe, our experiments were discontinued with a view to ascertain the particulars of the French plan, that it might be known whether we were traveling on beaten ground or not; but to the present time we have not obtained any specific description of it, nor do we know whether it consisted of a jet of steam discharged through the centre of a tube, as in Nos. 208, 210, and as applied to increase the draft of chimneys in locomotive carriages, or whether the jet was directed over the outside of a part or the whole of the end of the vacuum tube-nor have we learnt what degree of rarefaction was obtained. We have therefore concluded to insert the preceding notice of our labors, that since we cannot claim priority in the research, we may be allowed the credit, if any be due, for our modes of application, and the extent to which they carried the vacuum and are obviously capable of carrying it, especially by such devices as No. 220.

The whole of the devices, from the blowing tubes described in the last chapter to the apparatus for boiling sugar in vacuo described in this, with the exception of the patented plan of raising water by a series of vessels on different levels, originated entirely with ourselves, nor were we indebted either directly or remotely for so much as a hint in maturing them to any persons or writings whatever; and upon them we have also spent no inconsiderable amount both of time and money. But as we have on several occasions shown that new devices, so called, are often old ones, it is but just that we should mete to ourselves the same measure which we have given to others. We therefore with pleasure record the fact, that at a meeting of the Paris Academy of Arts and Sciences, held in January, 1833, M. Pellatans read a paper on the dynamic effects of a jet of steam, of which a notice (not a description of the plan) was published in an English journal, and copied into the Journal of the Franklin Institute for March of the same year-vol. x, 2d series, p. 195.

There is also described in the London Mechanics' Magazine, vol. iii, p. 275, an experiment of a current of air from a bellows directed over the orifice of an inverted glass funnel, which was placed in a saucer filled with water. From this (which we did not see till recently) the blowing tubes described in the last chapter might, with a little ingenuity, have been deduced.

Chap. 4.]

Spouting Tubes:

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CHAPTER IV.

Spouting tubes-Water easily disturbed-Force economically transmitted by the oscillation of liquids -Experiments on the ascent of water in differently shaped tubes-Application of one form to siphons Movement given to spouting tubes-These produce a jet both by their ascent and descent-Experiments with plain conical tubes-Spouting tubes with air pipes attached-Experiments with various sized tubes -Observations respecting their movements-Advantages arising from inertia-Modes of communicating motion to spouting tubes-Purposes for which they are applicable-The Souffleur.

There is a simple mode of raising water which to our knowledge has never been adopted, nor yet suggested-viz. by straight and open pipes, or, as they might be named, spouting tubes.

Water is raised in the ram (No. 168) by the force which the liquid acquires in flowing through descending channels, but in the instruments to which we now refer, the same effect is produced by its momentum in passing up vertical ones. So far as respects the force of a liquid in motion, it makes little difference in what direction it moves-whether the liquid rise perpendicularly, or having first descended at one angle it ascend at another. A jet d'eau, deducting all resistances, rises with the velocity with which it would fall through the same space; but in practice, the velocity is diminished by the length, figure and dimensions of the channel through which the liquid flows, and of the ajutage from which it escapes. Every person's experience teaches him, that a very small force is sufficient to disturb a large body of water, and that the consequent movement of the liquid is long continued after the force is withdrawn. A stone dropt into a tank, or thrown into a pond, causes waves to rise and roll to and fro over their whole surfaces, and some time elapses ere the movements cease. Days and even weeks elapse after a storm is over before the ocean recovers its previous repose. This effect is the result of the great mobility of water; its particles move with such extreme facility among themselves, and so actively impart their motion to each other, that a force once communicated to them is long ere it becomes exhausted. It is the same to a certain extent when waves rise and fall within tubes; for although the friction of liquids against the sides of these channels is considerable, especially in small ones, still the force in the central parts is but slowly consumed. A device therefore by which the oscillation of liquids is employed in transmitting forces, will probably consume as little in the transit as any mechanical device known.

It has already been remarked, that the momentum of a flowing liquid. suffers less in passing through a short than through a long tube-through a straight than a crooked one; and we may add that this is more especially true when the figure of the tube is expressly designed to facilitate the passage of the moving liquid, instead of being uniform in its bore throughNow in these particulars spouting tubes are eminently superior to others, or they may be made so. They are short, straight, and of a form adapted to the rising wave within them.

out.

Motion is imparted to water in a spouting tube either by depressing the liquid below the orifice and then admitting it to enter, or by excluding it from the tube till the lower orifice of the latter be sufficiently immersed. If a pipe whose lower end is closed be plunged perpendicularly in water,

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Experiments with Spouting or Open Tubes.

[Book V. the liquid will rise within it the moment its end is opened; but it will depend upon the length and figure of the tube, and the relative proportion of its two orifices, whether the liquid rush up above the surface without, or slowly reach it and there remain.

The following are selected from a number of experiments made several years ago. Instead of closing the lower orifice, the upper one was closed with the fore finger, the confined air acting the part of a cork, and preventing the liquid from entering until the finger was removed.

EXPER. I.-No. 222, a cylindrical glass tube, 18 inches long and half-inch bore. Its upper orifice was closed air-tight by the finger, and the lower one then held four inches under the surface of the water in the vessel. Upon raising the finger, the liquid rose in the tube six inches; i. e. its momentum carried it two inches higher than the surface in the cistern, and after a few oscillations it settled at the same level. Cylindrical tubes of various sizes were tried at different depths, and the average extent of the rise (above the surface) was equal to half the length of the part of the tube immersed below the surface. If No. 222 dipped four inches, the rise was two-if eight inches, it was four-and if twelve, it was six. By contracting either orifice the effect was diminished.

EXPER. II.-No. 223, a tube slightly conical, 16 inches long, the diameter or bore of the large end half an inch, and that of the small end onethird of an inch. The rise of the liquid in this exceeded that in No. 222. When tried with the large end up, little or no rise took place.

EXPER. III.-No. 224, another tube, 18 inches in length, the diameter of whose upper orifice was three-sixteenths and of the lower seven-eighths of an inch. Four and a half inches of the lower part was cylindrical. When dipped four inches in water and the finger removed, the liquid rose but two inches above the surface. This was owing to the cylindrical form of the lower part of the tube, all the water that entered being required to fill the lower part. When the dip was six inches, the rise was five; when eight, the jet passed out of the tube and ascended sixteen inches. When the tube was lowered to ten inches below the surface, the jet rose thirty inches; and when the end of the tube was twelve inches under the surface, the jet ascended four feet and a half. Fourteen inches dip threw it six

Chap. 4.]

Experiments with Spouting or Open Tubes.

499

feet, and sixteen inches dip caused it to ascend over seven feet. The rise in cylindrical tubes, we have seen, bore the same relation to the dip at various depths; but this experiment shows that the elevation of the jet in conical tubes increases in a much greater ratio.

EXPER. IV. To include the extreme proportions between the two orifices, we next took a matrass or bolt head (No. 225) and cut a portion from the globe opposite the junction of the neck or pipe. The opening thus made was 3 inches, and the orifice of the tube three-tenths. When the lower end was thrust two inches below the surface, scarcely any rise took place upon removing the finger; and when half the length of the whole was immersed, say ten inches, the rise did not exceed six or seven. The reason was plain: the large volume of air contained in the lower part could not be expelled instantaneously by the pressure of the liquid column. through the small orifice above, but the force of the ascending liquid was consumed in doing this. Various portions were now cut from the lower part, with a view to ascertain the greatest rise that could be obtained with a dip of four inches. This occurred when the diameter of the lower end was reduced to 12 inches: the liquid then rose between nine and ten inches above the surface. The upper end was now heated in the flame of a lamp, and the bore enlarged by pressing into it a tapered piece of wood, till the end resembled the conical ajutage C D in No. 201. This caused the liquid to rise an inch higher.

EXPER. V. A number of conical tubes of the same length, (21 inches) whose wide ends diverged or flared differently, were next procured, with the view of selecting those through which the jet rose the highest, as affording an approximation to the best form. The one represented at No. 226 gave a better result than any other. With a dip of four inches the jet rose thirteen. The diameter of its lower orifice was 1.6 inches, and that of the upper one .4: three inches below the latter, the bore was .2. At seven inches from the small end, the bore was .3—at fourteen inches, .4—and at seventeen inches, .5. The curve given to the flaring part of the lower end should be that which the fluid itself assumes in entering; but that given in the figure is sufficient for all practical purposes to which small instruments of this kind are applicable.

Before proceeding we may observe, that these instruments, simple as they are, and even when charged in the manner indicated above, are susceptible of some useful applications; among which may be named siphons. If the tube No. 226 were bent in the form of one, it might be applied in numerous cases to transfer acids or other liquids; and as it would be charged by the mere act of inserting its short leg into the liquid to be withdrawn, there could be no danger from sucking, &c. as in using the ordinary instrument. It will moreover be perceived from the third experiment, that the extent to which these siphons are applicable increases with the depth to which the short leg can be immersed: but as this chapter is appropriated to the application of spouting tubes to raise water from one level and discharge it at a higher one, their employment as siphous will be illustrated in a subsequent part of this volume.

It will at once occur to every machinist, that to render these tubes of any practical value for raising water, some mode of working them very different from that of alternately opening and closing the upper orifice with the finger, and raising them wholly out of and then plunging them into the liquid, would be required: a mode of regularly and rapidly depressing the liquid within them, that the wave formed by its ascent might rise and fall uniformly.

There is a simple way of doing this :-If the whole of the tube No. 227

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Raising Water with Open Tubes.

[Book V. be sunk perpendicularly in water, except one or two inches by which it is held, and then raised eight or ten inches, air will enter the small orifice and fill the part previously occupied by the liquid: if the upward movement be very slow, the air will gradually fill the interior without disturbing the surface of the liquid; but if the tube be raised by a rapid movement or slight jerk, the air will then rush into the void with a force that will push down the liquid before it to a considerable depth, so that on the reascent of the liquid its momentum will project a portion in the form of a jet, precisely like Nos. 224, 225 and 226. It is surprising how elevated a wave is generated in the tube by the slightest ascent of the latter, provided its movement be made sufficiently quick. The rise of the water, too, follows that of the tube so rapidly that most observers at first suppose them to rise simultaneously. The fact is, the liquid when depressed returns with such velocity as to escape from the tube the instant the stroke is finished, and even before its motion be slackened.

EXPER. VI. A jet may be produced by the descent of the tube as well as by its ascent. Let No. 228 be so held that its lower end dip not more than an inch or an inch and a half in the water, and then be pushed quickly down eight or ten inches-a stream will be projected from its upper orifice to an elevation of six or seven feet, and will be instantly followed by another that will reach nearly as high. The same cause operates here as in the upward movement, but it is differently excited. A small part only of the air within is expelled at the end of the stroke, on account of the tube's rapid descent, and consequently the water is prevented from entering; but as soon as this movement of the tube ceases, the liquid rushes in and a portion ascends in the form of a jet. On the subsequent ebb of the wave within, another one rises nearly equal to the first, and causes the second jet. The following experiment will illustrate both movements :— A small glass tube eight inches long, its wide end an inch and five-eighths diameter and its small end one-eighth, was employed. By its upward movement or stroke the extremity of the jet reached to an elevation of nine feet. By the downward stroke a jet rose six feet, which was succeeded by another that reached four feet and a half. Now if both movements are properly combined in a spouting tube of large dimensions, we believe the instrument may be made to raise as much water, in circumstances adapted to its employment, as any other hydro-pneumatic machine.

In

If the figure given to No. 226 should be found better adapted than any other when the tube is used as a siphon, it does not therefore follow that the same form would be the most suitable to produce jets of water. the former case the instrument acts while at rest, but in the latter a constant and rapid movement is required: hence, to prevent an unnecessary expenditure of the power employed, it should be so formed as to present as little opposing surface to the resistance of the dense fluid in which it works as is consistent with the elevation, or quantity of water to be raised by it. This remark applies particularly to the lower or wide end, for if that part be suddenly expanded or flared like a trumpet, a volume of water of equal diameter has to be displaced in the reservoir every time the tube is pushed down, and also a ring of water whose external diameter is the same (the internal one being bounded by the tube) every time the latter is lifted up. When used as spouting tubes the lower end should therefore flare very little, if any, unless in cases where the outlay of power to work them is of little consequence or of secondary importance. The upper end of a spouting tube, when intended to throw jets from its orifice, should not diverge like that of No. 226, since the elevation of the stream would be thereby diminished: instead of rising in a compact jet, it would