472

Gunpowder and Vapor Engines.

[Book IV. muzzle of the other barrel. Now let that musket with whose breech the plug of its ramrod is in contact be first fired, and the rod will instantly be forced like a bullet up the barrel, and by its connection with the beam will cause the other rod to descend. The musket in which this last rod moves is then in its turn to be fired and the rod forced up in the same way. Thus the operation is continued. The reciprocating motion of the beam is converted, if required, into a continuous rotary one by means of a crank or some analogous device.

Engines on this plan have not succeeded, nor is there any probability of their success. There are apparently insuperable objections to them, but which need not here be detailed. The explosion of gunpowder has therefore been more frequently employed to produce a partial vacuum in a cylinder when its piston is raised, in order to excite the pressure of the atmosphere to force it down. Suppose one or more openings, covered by valves or flaps, were made near the upper ends of the muskets mentioned above, i. e. just beneath the pistons or plugs of the ramrods when at the highest point in the barrels, and the powder exploded when they are in that position: the sudden expansion would drive out through the valves most of the air previously in the barrel, the valves would instantly close, and the atmosphere would push down the rod and thus raise the other; which in its turn might be caused to descend by exploding the charge under it, and so on continually. Instead of openings in the cylinders for the escape of the air, some experimenters have made large openings in the pistons and covered them with flaps, (like the suckers of common pumps) so that when the explosion ceased the flaps closed and prevented the air's return. Others have used solid pistons and removed the bottoms of their cylinders, and covered the openings with leather flaps so as to operate as valves and give a freer exit to the air and heated gases. This was the plan adopted by Mr. Morey. Papin used hollow pistons. The vacuum produced in this manner by gunpowder has always been very imperfect. Instead of obtaining a pressure of 14 or 15 pounds on the inch, Papin could not realize more than six or seven.

Gunpowder has also been applied to raise water directly, by exploding it in close vessels like the receivers of Savery, with a view to expel their contents by its expansive force, and also to produce a vacuum in order to charge them-but with no useful result.

Explosive mixtures, formed of certain proportions of an inflammable gas and common air, have been found to produce a better vacuum than gunpowder; for a volume of air equal to that of the gas used is displaced from the cylinder by the entrance of the gas previous to every explosion, and when this takes place nearly the whole of the remaining air is expelled. As yet, however, the best of explosive engines have had but an ephemeral existence. Besides other disadvantages, the heat generated by the flame attending the explosion expands the air that remains, so as to diminish considerably the effect.

Of vapor engines, the most promising at one time were those in which the moving force was derived from ether and alcohol. The former boils at about blood heat, or 98° of Fahrenheit's scale, and the latter at 1740, while water requires 2120. The vapor of alcohol, it has been stated, exerts double the force of steam at the same temperature; and if to this it be conceded that the same quantity of fuel produces equal temperatures on both alcohol and water, then the former would seem to be more economical than than the latter. Moreover, in consequence of the different specific gravities of water, alcohol and ether, the cost of vaporizing equal volumes of each varies in a still greater ratio than their boiling points

Chap. 9]

Vapor Engines Woisard's Machine.

473

this cost being as the numbers 11, 4, 2-thus making the scale preponderate still more in favor of alcohol and ether. Why then, it may be asked, have they not superseded water? Principally because the different vo lumes of vapor from equal quantities of the three liquids turn back the scale in favor of steam. A cubic inch of water affords 1800 cubic inches of steam, while a cubic inch of alcohol produces about 600 and ether only 300 inches; hence the expense of producing equal volumes of vapor (and that is the main point) is actually in favor of steam. It has therefore been deemed more economical to use this fluid than the others, even if they were equally cheap-to say nothing of the danger arising from such an employment of highly inflammable liquids, and the practical difficulties attending their application.

In 1791, Mr. John Barber obtained a patent for an explosive motive engine he used gas or vapor from "coal, wood, oil, or any other combustible matter," which he distilled in a retort, and "mixed with a proper quantity of atmospheric or common air." See Repertory of Arts, vol. viii, 371. Another patent was issued in 1794 to Robert Street, for an "inflammable vapor force," or explosive engine. He exploded spirits of tar or turpentine mixed with common air under a piston, and forced it entirely out of the cylinder, into which it was again returned (by its own weight) and guided by grooves in the frame work. Repertory of Arts, vol. i, 154. In 1807, a patent was granted in France to M. De Rivaz, for another, in which hydrogen and common air were mixed and exploded. De Rivaz moved a locomotive carriage by the power he thus derived. He also inflamed the gaseous mixture by the electric spark. Dr. Jones, in 1814, made experiments on another. See Journal of the Franklin Institute, vol. i, 2d series, page 18. Mr. Cecil, in 1820, published in the Transactions of the Cambridge Philosophical Society, (Eng.) a description of an explosive engine of considerable merit.

In 1825, Mr. Brown, of London, patented his pneumatic or gas vacuum engine. The very sanguine expectations it excited have now died away. It is figured and described in too many works, both English and American, to require insertion here. In 1826, Mr. Morey, of New Hampshire, patented an explosive engine, and soon after exhibited a large working model in this city, (New York) which we took several opportunities to examine. The piston rods of two vertical and open cylinders were connected to the opposite ends of a vibrating beam. The pistons were made of sheet copper, in the form of plungers, about nine inches diameter, and were made to work air-tight by means of a strip of oiled listing or cloth tied round the upper ends of the cylinders. This was all the packing. Mr. Morey employed the vapor of spirits of turpentine and common air. A small tin dish contained the spirits, and the only heat he used was from a common table lamp. By means of a crank and fly-wheel a rotary movement was obtained, as in the steam-engine.

A singular device for making the atmospheric changes of temperature a means for raising water, was devised by M. Woisard. It consisted of two vessels, one above the other, connected by a tube. The lower one, having a valve in its bottom, was placed in the water to be raised. The upper vessel was exposed to the sun's heat, and within it was a bag or small balloon containing air, and a little ether, or other volatile liquid. "As the atmospheric temperature falls, the balloon will diminish in bulk, the surrounding air will become rarer, and the water will introduce itself into the machine through the valve; and when the temperature again rises, the pressure exerted within the machine by the increasing volume of the balloon, will cause the excess of water to flow out." With the ex

474

Decomposition and recomposition of Water.

[Book IV.

ception of the ether, this device is a modification of the air machines Nos. 174 and 175, figured at page 380.

The vapor of mercury has been tried as a substitute for steam, but without much success. This metal boils at 660°.

Another source of power has been sought in the tremendous force with which the liquefied and solidified gases expand at common temperatures. Liquid carbonic acid, at the low temperature of 32°, has been found to exert a force equivalent to thirty five atmospheres! and every increment of heat adds to its energy. No very practical mode of employing this force as a mechanical agent has yet been matured.

The alternate decomposition and recomposition of water has also been suggested. By decomposing this liquid by galvanic electricity, oxygen and hydrogen gases are produced in the exact proportions in which they combine in water. If these gases be made to occupy the interior of a cylinder when the piston is raised, and the electric spark be then passed through them, they instantly become condensed into a few drops of water, and an almost perfect vacuum is the result, when the atmosphere acts on the piston. The water is then to be reconverted into its constituent gases, and the operation repeated. See "The Chemist," for 1825. For further and more recent information respecting motive engines, consult the Repertory of Arts, Hebert's Register of Arts, London Mechanics' Magazine, and the Journal of the Franklin Institute.

END OF THE FOURTH BOOK.

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 encom passed 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

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