Chap. 9.]

Explosive Engines.

471

and other mills; and he thinks in the hot months, at least, a steam-engine might be made to raise by the sun's heat water enough from a well to replenish fish ponds &c. as opportunity served. We have long thought that solar heat will yet supersede artificial fires to a limited extent in raising steam, as well as in numerous other operations in the arts, especially in places where fuel is scarce. It is a more legitimate object of research than one half of the new projects daily brought forward.

The mode adopted by Watt for supplying water to his boilers by means of a float attached to a lever, and so arranged as to open and close a valve in an adjoining cistern, was not invented by him. It was employed by Mr. Triewald, the Swedish engineer, in 1745, in his apparatus for communicating heat to green-houses by steam, and is described, with a figure, in the London Magazine for 1755, p. 18–21.

Heating green-houses by steam is mentioned by an English writer in 1660. Rivius, in 1548, speaks of eolipiles being employed to impart an agreeable temperature to apartments in dwellings. Col. Wm. Cook's Method to warm rooms by the steam of boiling water," is described, with a cut, in the Gentleman's Magazine for 1747, p. 171. A boiler was to be heated by the kitchen fire, and the steam pipe to ascend through one tier of rooms, and descend through another, traversing backwards and forwards in each room according to the temperature required; the escape of the condensed and waste steam being regulated by a cock.

A patent for cooking by steam was taken out in England by Mr. Howard in 1793. He named his apparatus "a pneumatic kitchen." Repertory of Arts, vol. x, 147.

There are two other classes of motive machines that we intended here to notice in some detail; but as they have not come into general use, and this volume having already nearly reached its prescribed limits, a brief sketch may suffice. The origin of most of them may be traced to attempts to supersede steam by more portable fluids, or such as require less fuel to generate. We allude to explosive and to vapor engines. Of all the devices to which the steam-engine has given birth, none possess greater interest than these. Some were designed to raise water directly, and all of them indirectly. The first class are named from the force by which they act being developed by the firing (generally under pistons) of explosive compounds. These are either concrete or aëriform substances, as gunpowder, a mixture of hydrogen gas and common air, &c. Those of the second class are similar to steam-engines, except that they are worked by elastic fluids evolved from volatile liquids, or such as pass easily and at low temperatures into the aëriform state, as alcohol, ether, &c.

Explosive like steam engines have been made to act in two different ways, according to two opposite properties or effects of the exploded substance the expansive force developed, and the vacuum or partial vacuum which succeeds. For the purpose of explanation, suppose two large repeating guns or muskets, provided with small charges of powder only, to be secured by a frame in a perpendicular position, with their muzzles upwards, and three or four feet apart. Directly over them let there be adapted a working beam, somewhat as in the last figure, suspended on a fulcrum at an equal distance from each. Suppose the ramrods placed in the barrels with their buttons or plugs so made as to fill the bore, and work air-tight like the piston of a syringe or pump. Let the upper ends of these rods then be connected by a bolt to the ends of the beam, which should be at such a distance above the muzzles that when the plug of one rod is at the bottom of its barrel, that of the other may be just within the

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 980 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 volumes 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.

away.

In 1825, Mr. Brown, of London, patented his pneumatic or gas vacuum engine. The very sanguine expectations it excited have now died 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 320, 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.