Page:A Treatise on the Steam Engine (1847).djvu/16

 The history of the steam engine is divisible into five great epochs. The first extends from the times of the ancients to the first effectual application of the boiler, which appears to have been accomplished by the Marquis of Worcester, and it was this single step that turned the toys of Hero and De Caus into a true and useful steam engine. The second epoch is distinguished by the employment of a vacuum as an aid to the simple pressure of the steam. The third epoch relates to the successful application of the cylinder. The fourth to the condensation of the steam by injection, to the movement of the valves by the engine, and to the various improvements in detail, which were carried into effect by Smeaton. The fifth epoch is that distinguished by the application of the condenser, and the other improvements of Watt, which brings down the history to our own times; as since the steam engine left the hand of Watt, no improvement involving a new principle has been added to the list. Under each of these heads we have a few observations to offer.

FROM THE TIMES OF THE ANCIENTS TO THE INTRODUCTION OF THE FIRST FEASIBLE STEAM ENGINE.

The ancients appear to have had very vague notions of the nature of steam. They believed in the existence of only four elements—fire, air, earth, and water; and thought that water was turned into air when dissipated by evaporation. Thus Plato says, "That which we now call water becomes as a stone, or solid, but being melted and diffused becomes gas or air;" and it was the prevalent notion of his time, and of many subsequent ages, that water is turned into air by heat. In consequence of this misconception, it is often difficult to understand, in the description of ancient pueumatic contrivances, whether steam or air was the moving power, and we have indeed generally to form our conclusion on this head from the nature of the arrangement. We have, however, very clear evidence that both steam, and air expanded by heat, were often used by the ancients as motive powers, and some of the expedients employed for that purpose are of considerable elegance. In a work which has been often referred to, entitled Spiritalia seu Piteumaticu, written by Hero, a philosopher of Alexandria, about 130 years before the Christian era, a variety of devices are set forth for elevating liquids, and obtaining rotatory motion by means of air and steam, of which we shall only enumerate those in which it is beyond doubt steam was the agent. The first of these is a method of causing w ine to flow from the hands of effigies set beside an altar, after the fire upon the altar has been lighted. A steam-tight vessel or vase, containing wine, is placed within each effigy, and the altar is made hollow, and is partly filled with water, bent pipes being conducted from the space above the water iu the altar to the spaces above the wine in the vases, and other tubes again being led from beneath the level of the wine in the vases to the hands of the effigies. When, therefore, says Hero, you are about to sacrifice, you must pour into the tubes a few drops, lest they should be injured by heat, and attend to every joint, lest it leak; and so the heat of the fire mingling with the water will pass in an aerial state through these tubes to the vases, and pressing on the wine make it pass through the bent syphons, until, as it flows from the hands of the living creatures, they will appear to sacrifice as the altar continues to burn.

The instrument for the production of rotatory motion is one of great ingenuity, and has all the qualities of a true and efficient steam engine, except its size. This instrument is called the ./Eolipile, and is identical in all its material features with the engines lately constructed by Avery in America, and Ruthven of Edinburgh, in this country. These engines are more expensive in steam than ordinary engines, and travel at an inconvenient speed; but in other respects they are quite as effectual, and their construction is extremely simple and inexpensive. The substance of Hero's recipe for the construction of an /Eolipile is this. Let a boiler be set on the fire, and nearly filled with water, and let its mouth be closed by a cover which is pierced by a bent tube, whose extremity fits exactly into a hollow sphere. But at the opposite end of the diameter (of the sphere) let there be an iron axis supported from the top of the cover, and let the sphere have two bent pipes at the ends of a diameter of the sphere, perforated therewith, and bent round in opposite directions; and let the bends make right angles, and be in the plane perpendicular to the axis. Then it will follow that the boiler being heated, the vapour passing through the tubes into the sphere will rush out through the reversed pipes, and whirl the sphere round on its axis.

Hero specifies another modification of this instrument for giving motion to automaton figures, so as to induce the idea of supernatural intervention among the superstitious multitude by whom the heathen temples were frequented; but here heated air, instead of steam, is made the pritmim mobile, in order that the inciting power may be invisible. There is no doubt that pueumatical contrivances were extensively employed by the priests in ancient times for deluding the people, and it is easy to conceive that such treatises as that of Hero, which discovered the nature of those pious frauds, must have been the occasion, at the time, of infinite scandal. The celebrated statue of Memnon, which uttered sounds every morning at suurise, was, no doubt, indebted to some such artifice as one of those described by Hero for its mysterious power. Very few of the devices he mentions are of his own invention, but most of them existed for ages before his time, although the knowledge of their structure and mode of operation appears to have been confined chiefly to the priests.

On the revival of classical learning throughout Gothic Europe the «.n of Hero attracted earnest attention, and several translations of it »<-rs= i^. which afforded an early exercise to the infant art of priutiug. A xmrvledge of the expedients of the ancient mechanicians was thus **suy diffused, and it was probably one of them that was reproduced in Spaa c 1543 by Blasco de Garay, a sea-captain, for the propulsion of vessels. T. contrivance, whatever may hove been iu real nature, appears to have Scl very effectual. Commissioners were appointed by the Emperor Chaxlf? r to test the invention at Barcelona on the 17th of June 1543, and the rtaj was that a ship of 200 tons burden was propelled by the marbnne x! <*rate of three miles on hour. Nothing further is known of the iovtBU^. than that the vessel was propelled by paddle wheels, and that the mortar force was derived from a boiler containing water, which, it wan vud. «« liable to explode. It appears unaccountable that after the Successful It* realised by Garay, no further step should have been taken respcciinj; 1~j plan. He was rewarded by the Emperor, and promoted into a higher rvtt. but his ingenuity does not appear to have been ever turned to any ustii account, and his scheme was never introduced into practice.

The various works on mechanics, published about the close of the <a.~ teenth century, are full of expedients for the elevation of water similar to those of Hero, but much less refined; and Bapiista Porta, in his bcs'l st Pneumatics, published at Naples in 1601, incidentally makes rocnnm, .: the following contrivance, not indeed as any discovery nf his own. ^smerely as an arrangement of convenience, in an experiment for afecrtauraut the relative bulks of water and steam. "Construct a box of ;rU* ut no. having a hole at the bottom through which is introduced the neck of a iui. containing one or two ounces of water, and let the neck of th« flank he u< luted to the bottom of the box that there be no leakage. Near th<r hotsoa, of the box let a pipe ascend, but at such a distance from the bottom m a« permit the water to get out, which pipe passing through the cover u in ri« a short distance above it. The box is to be filled with water by an apertan which is afterwards to be closed up, steam tight . This being done. pt*-r the flask upon the fire, and as it becomes slowly heated, the water brh{ gradually dissolved into air will press upon the water in the hot.. and acu.forcibly against the water which issues through the pipe, will not cscai and if we continue the heat, the whole of the water subjected to it wili U evaporated, and during such evaporation the air will constantly press Oipu the water in the box, and the water will constantly spring from it.- A similar arrangement is mentioned in a work by Solomon de Cans, a Ba;t of Normandy, or at all events a Frenchman; not for the philucoplixs! purpose mentioned by Porta, but merely as an illustration that water nut*. be raised above its level by fire, a truth known from the remotest antiqmty The work of De Caus, to which we have referred, is entitled Lts ffti—w des Forces Mouvantes uvec diverses Machines lant utiles que plauaalcm. Pats. 1623, This work is dated Heidelberg, 1615, and the first edition «ppo.-< to have been published at Frankfort: it contains the following mmmz several other theorems of equal insignificance: —" Take a ball of copper ir* I soldered at every part; it must have a vent-hole to put in the water. c<l also a tube which is soldered to the top of the ball, the end of which approaches near to the bottom of the ball without touching it. After nlhus this ball with water through the vent-hole, stop it close and put it on iis fire; then the heat striking against the ball will cause all the water to pu« through the tube." De Caus also mentions a scheme of a solar fountain. ►*; it, as well as the preceding, are merely clumsy imitations of some oi ti* contrivances described by Hero. He gives the following illustration of the great force of steam:—" Take a ball of copper of one or two feet dimmcrr and one inch thick, which being filled with water by a small hole «absequently stopped by a peg, so that neither air nor water can est.ape. it < certain that if the said ball be put over a great fire so that it may Wcaisvery hot, it will cause so violent a compression, that the ball will be shar tered in pieces." The great force of steam, however, was very well knei.' to the ancients, who even went the length of ascribing earthquakes to prTd up vapours, generated by subterranean heat; and for ages the lime l«m thing like the numerical appreciation realised by such experiments as tt:. of De Caus. We confess that we are at a loss to understand wherein thif numerical appreciation can consist, for although De Caus or Rivauh ma? have ascertained that steam will burst a certain hall or bomb, they «rr«r ascertained what sort of ball or bomb steam will not burst, so that thrv did not establish any limit to the power of steam, but only showed that it o capable of very powerful effects This, however, was known long previous'. and in attributing to the force of pent up steam even such stupendous V>3«motions as earthquakes—the upraising of continents and rending asun..s*of mountains—the ancients must have had at least quite as magniftrent ides.s of the force of that mighty agent as is to be afforded by the bursting of * ball or bomb, and we cannot perceive in what way an experiment establitis any thing which only proves that the power of an agent is adequate to tie production of effects far more paltry than are known to be within the races of its capacity.

A contrivance for obtaining a rotatory motion from steam is describni Giovanni Branca, in a work published at Rome in 1629, entitled Machine; volume nuovo et di multo artificio da fare effetti muratqiom