BOOK V.

NOVEL DEVICES FOR RAISING WATER, WITH AN ACCOUNT OF SIPHONS, COCKS, VALVES, CLEPSYDRÆ, &c. &c.

CHAPTER I.

Subjects treated in the fifth book-Lateral communication of motion-This observed by the ancientsWind at the Falls of Niagara-The trombe described-Natural trombes-Tasting hot liquids-Waterspouts-Various operations of the human mouth-Currents of water-Gulf stream-Large rivers-Adventures of a bottle-Experiments of Venturi-Expenditure of water from various formed ajutagesContracted vein-Cause of increased discharge from conical tubes-Sale of a water power-Regulation of the ancient Romans to prevent an excess of water from being drawn by pipes from the aqueducts.

In this book we propose to notice some devices for raising water that are either practically useful, or interesting from their novelty or the principles upon which they act. An account of siphons is added, and also remarks on cocks, pipes, valves, and other devices connected with practical hydraulics.

A fluid moving in contact with another that is comparatively at rest, drags along those particles which it touches, and these by their mutual adhesion carry their neighbors with them; the latter also communicate the impulse to others, and these to more distant ones, until a large mass of the fluid on both sides of the motive current is put in motion. Whatever may be the process by which this is effected, or by whatever name the principle involved may be called, (lateral communication of motion or any other) there is no question of the fact. The operation moreover is not confined to any particular fluid, nor is it necessary that the one moved should be of the same nature as the mover: thus air in motion moves water and other liquids as well as air, and aqueous currents impart motion to aëriform fluids as well as to standing waters. A stream of wind from a bellows bears with it the atmospheric particles which it touches in its passage to the fire-i. e. it sweeps along with it the lining of the aerial tube through which it is urged. Blowing on a letter sheet to dry the ink, or on scalding food to cool it, brings in contact with these substances streams of other air than what issues from the thorax. The operations by which the man in the fable blew hot and cold "out of the same mouth

a Does not the same principle perform an important part in respiration ?—the lungs not being wholly inflated by air directly in front of the lips, where particles of that previously exhaled might still linger, but also by currents flowing in from all sides of the mouth or nostrils.

476

The Trombe.

[Book V. may here be explained: in the first case the hollow hands closely encompassed the mouth and received the warm air from his chest; in the latter, his food was at a distance from his lips, and consequently the heat of his breath was absorbed by the surrounding air and that which was carried along with it to his soup.

A blast of wind directed over the surface of a placid pond or lake not only creates a current on the latter, but sometimes bears away part of the water with it. A vessel sailing before the wind is aided in her course, though it may be but slightly, by the liquid current produced on the ocean's surface. Storms of wind long continued heap up the sea against the mouths of rivers, and cause them to overflow their banks, while low tides often result from the same agent driving the ocean away in opposite directions. These effects of wind were observed in remote ages. "He raiseth the stormy wind which lifteth up the waves." The river Jordan was "driven back" by wind, so that "all the Israelites passed over on dry ground." By its agency, a passage for the same people was opened through the Red Sea. "And Moses stretched out his hand over. the sea, and the Lord caused the sea to go back, by a strong east wind all that night, and made the sea dry land, and the waters were divided." Exodus

xiv. 21.

On the other hand, rivers and water-falls bear down immense quantities of air with them. Strata of this fluid on the surfaces of rapid streams acquire a velocity equal to that of the latter, and in some places aerial currents thus produced are very sensible. At Niagara they are sufficient to drive mills or supply blasts for a long line of forges. In 1829, while ascending the path on the Canadian side, in order to pass under the grand chute, we entered suddenly into one of those invisible currents under the Table Rock, and were nearly prostrated by it. It is the ascent of this air loaded with minute particles of water, (which are borne up by it in the same manner that it is itself carried down) that contributes to the formation of the solar and lunar rainbows seen at the great North American and other cataracts. Heavy rains bring down oceans of air, and in the shower bellows, or trombe, blasts of wind are produced on the same principle. Could we see the air brought down by heavy showers, we should behold it rebounding from the earth, something like smoke when driven against a wall or any other plane surface.

B

A

C

As the trombe illustrates this part of our subject, a figure of one may as well be given. The pipe A discharges water from a reservoir into a funnel placed on the vertical tube C. The end of A terminates in the funnel, and opposite to it is made a number of openings in C, two of which are shown in the cut. The lower end of C enters the close vessel D, and discharges its contents on a stone placed directly under it. As the water from A passes down C, it draws air along with it through the top of the funnel, and also through the holes in the upper part of C. As the liquid dashes against the stone, the air separates and rises to the top of the vessel, whence it is forced by successive volumes through B to the fire, while the water collects at the bottom and is let off by a regulating valve or cock. This machine it will be perceived is a miniature imitation of some of nature's operations; for cascades, water-falls, and also No. 198. The Trombe, heavy showers of rain, are all natural trombes.

D

Chap. 1.]

Gulf Stream.

477

The trombe is of considerable antiquity. It was known to Heron, and is referred to in Pliny's Natural History. Kircher has given several figures of it. See tom. i, 203, of his Mundus Subterraneus, and tom. ii, pp. 310, 347, of his Musurgia Universalis; in which last work he shows its appli cation to supply wind to organs, and by discharging the water from the bottom of the vessel upon a wheel he imparted motion to the keys of those instruments. See also Phil. Trans. Abridg. vol. i, 498.

Liquids raised by currents of air may be illustrated by operations in common life. Whenever water in a well settles to a level with the orifice of the pump pipe, air rushes in (on the ascent of the sucker) and sweeps up with it portions of the liquid in the form of dense rain. On the same principle people are enabled to taste scalding liquids. The next time the reader sips hot soup, or tea, or coffee, he will find himself involuntarily keeping the edge or rim of the spoon or vessel a short distance from his mouth, and protruding his lips till the upper one projects a little over the edge then drawing in his breath, the entering air ripples the surface of the liquid, and by its velocity bears broken portions along, precisely like the pump just mentioned. The liquid particles being thus mixed with comparatively large volumes of cool air, are so reduced in their temperature as to be received without injury and without inconvenience.a

Water-spouts appear to be charged in much the same way, whatever may be the active agent in the formation of these singular phenomena; for the sea immediately under their orifice has often been observed to bubble or boil violently, and rise into the spout in disjointed masses.

A stream of water directed into or through a body of the same liquid, also communicates motion to those particles of the latter that are in contact with or adjacent to the current. Examples of this are furnished in several of nature's hydraulic operations. That constant oceanic current produced by the trade winds is one. It sweeps round the globe, but is deflected and divided by the varying configuration of the lands that lie in its way. Under the torrid zone, it passses through the Pacific and Indian oceans, whirls round the southern point of Africa, inclines to that continent in again approaching the equator, then stretching across the Atlantic is divided by the South American coast-one part turning northward to the Gulf of Mexico-thence this last division issues as the Gulf Stream, and being turned in an easterly direction by the coast of the United States, it bears away past the banks of Newfoundland, and extends its influence to Ireland, Iceland, Norway and the North Sea. This mighty current not only draws with it the liquid channel through which it flows, but the ocean for leagues on each side is carried along with it, or follows in its train;

a Some of the operations of the mouth are deserving of particular notice. They will be found to elucidate several philosophical principles, and attention to them would certainly have enabled inventors to have anticipated many useful discoveries. We have in a preceding book observed that the mouth is often employed as a forcing pump in ejecting liquids, and as a sucking one when drawing them through siphons, or through simple tubes. We have just seen how it raises hot liquids by drawing a stream of air over them, and machines on the same principle have been made to raise water. It is often used as a bellows to kindle fires, and every body employs it to cool hot victuals by blowing. It even acts as a stove to warm our frozen fingers, by giving out heated air. Many make a condensing air-pump of it, to fill bladders, air-beds and air-pillows; some make an exhausting one of it, and in all it acts continually as both in respiration. How often does it perform the part of a fife, an organ, or a whistle, to produce music? -of an air-gun to shoot bullets and arrows from the sarbacan ?-and, not to weary the reader, when employed in smoking a pipe of tobacco, we see in operation the identical principle of increasing the draft of locomotive chimneys by exhaustion-i. e. a sucking apparatus is applied to that extremity of the flue that is the farthest from the fire-a device patented in Europe a few years ago.

478

Water raised by currents of the same liquid.

[Book V.

and thus it is incessantly transferring to northern latitudes the warm waters of the equinoctial regions.a

The volumes of water which shoot from the mouths of the Amazon, Oronoco and Mississippi, continue with almost unabated velocity for leagues into the sea, and impart motion to the contiguous portions of the latter, which are compelled to accompany them in their course.

A current of water not only imparts motion in this manner to a mass of the same liquid when on a level with itself, but it may be applied to raise water from a lower level. This at first sight does not appear very obvious. A person having a field which he is unable to drain for want of a place of discharge sufficiently low for the purpose, would hardly think his object could be obtained by passing a rapid stream into it from a higher level. To some farmers this would seem the most direct way to deluge the land; yet the thing is not only possible, but in some cases quite easy, as will appear from the following experiments made by M. Venturi in 1797.

From the lower part of the cistern D, No. 199, a horizontal tube proceeded into the vessel A C. The water in D was kept at 32 inches above the centre of the pipe. Opposite and at a short distance from the pipe was placed the mouth of an inclined rectangular channel or gutter, open at top. The water issuing from the pipe rushed up this channel, and was discharged at B; but as it entered the gutter, the current dragged in with it the contents of A C, until the surface sunk from A to C. From this experiment it is obvious that land on a low level, as at C, might be drained in this manner, and the water discharged above, as at B, whereever a motive current could be obtained. Venturi applied the principle with success to some marshy land belonging to the public.

In the next experiment both air and water are moved by the current, and the pressure of the atmosphere excited to raise water as in the pipe of a pump. The cylindrical tube K (No. 200) was connected to a reservoir of water, D, the surface as before being 32 inches above its orifice. The pipe K was 18 lines in diameter and 57 long. A glass tube A B was connected to its upper surface at the distance of eight lines from its junction with the reservoir. The other end of the glass tube descended into a vessel, T, containing a colored liquid. When water flowed through

No. 199.

T

No. 200.

a Floating substances have often been thrown into the Gulf Stream to ascertain its direction. Upwards of twenty years ago we cast overboard, near the Banks, a common quart bottle carefully corked and sealed, and having a few inches of red bunting tied to the neck The bottle contained a letter addressed to a gentleman in London, and an open note in English and French, requesting the finder to put the letter into the nearest post-office, American or European, and also a memorandum of the circumstances, date and place of its discovery. Precisely eleven months from the day the bottle was committed to the deep, the letter was delivered by the postman, and accompanied with another from an Irish clergyman. The fragile vessel floated safely ashore near Sligo. Its little pennon excited the attention of a peasant, who broke the bottle, and not knowing what to make of the contents, carried the whole to his priest. This gentleman politely forwarded the letter to its destination, and wrote another containing the particulars just mentioned. Both letters, we believe, were laid before the British Admiralty by the gentleman to whom they were addressed.

Chap. 1.]

Vacuum produced by liquid currents.

479

K it dragged the air at the mouth of the glass tube with it, the remaining air dilated, and finally the whole was carried out with the effluent water, and the colored liquid rose to the height of 24 inches in A B. The glass tube was then shortened to about 22 inches, when the contents of T rose up and were discharged from K. In another experiment K was placed in nearly a perpendicular position, being inclined a little that the jet might not fall back on itself, but the liquid rose through A B as before. The end of A B where it joined K was flush with the interior surface of the latter. Several small holes were made round K; these diminished the velocity of the issuing current, but no water escaped through the openings. There is a singular fact relating to the discharge of liquids from different shaped ajutages: for example, more water flows through a short tube than through a simple orifice of the same diameter. A circular opening, of the same diameter as the bore of K in the last figure, was made in a sheet of tin, and the latter attached to a cistern in which the water was kept at a constant altitude of 32 inches: now while four cubic feet of water escaped through the opening in 41 seconds, an equal quantity passed through K in 31 seconds; and when the length of K was only twice its diameter, the quantity discharged was still greater.

But the quantity discharged may be still further increased if the end of K next the reservoir be made to assume the form of the contracted vein. This term is used to designate that contraction which a liquid column undergoes when escaping through an orifice, or when entering a tube. Suppose an aperture, an inch in diameter, made in the bottom of a bucket or a cauldron, and closed by a plug. Then fill the vessel with water, and withdraw the plug. Upon examination the descending column will be found contracted or tapered for a short distance below the orifice, viz. half an inch, or half the diameter of the orifice. The area of the section of the smallest or most contracted part will be to the orifice as 10 to 16 according to Bossut, but when a short cylindrical tube was applied to the orifice, he found the contraction as 10 to 12.3. (The same thing occurs whether the opening be made in the side or bottom of a vessel.) Hence by enlarging the end of K next the reservoir, in the proportions named, the contraction within the cylindrical part of the tube would be avoided, and the discharge consequently increased.

By substituting for K a compound tube of the form and proportions figured at No. 201, the quantity discharged has been ascertained to be more than doubled, being to that delivered by the orifice in the tin plate as 24 to 10! A, the cistern; B, a short conical tube connecting the cylin