PRELIMINARY DISCOURSE.

A TREATISE on the Steam Engine would, we suppose, hardly be reckoned orthodox if it began in any other way than with an account of the doings of Savery, Papin, and the other patriarchs whose names figure in the history of steam invention. The devices indeed of these ancient worthies bear very little resemblance to the modern steam engine, and can throw but little light upon its structure or mode of operation; but it was out of these primitive contrivances that the modern steam engine arose, and they derive a sufficient dignity from that relationship to make them the objects of a just curiosity. We think, therefore, that some slight sketch of the expedients employed in the early career of steam improvement is but a reasonable prelude to a Treatise on the Steam Engine, and is indeed indispensable to the integrity of such a work: But we fear our qualifications for the task are by no means so conspicuous, for delineations of this kind require a light and graceful pencil, and become intolerable in the hand of a vulgar limner. The great art lies in saying just as much as the necessity of the case requires, and nothing more; for a history of the steam engine is the least important part of a treatise on that subject, and only deserves a space answerable to its insignificance; whereas by needlessly expanding this part of the work, or by elaborating trivial schemes into importance, the proper subordination of objects is destroyed, and all those discriminating shades are obliterated which constitute the excellence of the picture. To all this we must add that people in these utilitarian days have neither time nor inclination to listen to long-winded descriptions of exploded projects in steam machinery, though they might like well enough to know something of the nature of those expedients if it can be told them in a few words: But they are not likely to perplex themselves with such inquiries as, who first forced water above its level by steam pressure, or solicited it to rise by a partial vacuum? and to say the truth, such inquiries appear to us of about as much importance as the researches of those learned grammarians, who spend a lifetime in restoring a dative case, or adjusting a metre or an accent. The task, too, of resolving these frivolous problems is quite as tedious a one as that undertaken by the learned persons aforesaid; for after having ascended through history, by a most toilsome progress, to the first person guilty of disturbing the equanimity of water by steam pressure, the shade of some learned recluse who flourished in ancient times in China it may be, or Japan, will probably rise up with proofs of a still higher priority, and the idol just set up for universal adoration will be cast into the dust by this new authority, to be overthrown in its turn by the researches of subsequent enquirers. The fact appears to be, that the power of steam to raise water above its level was widely known in very ancient times, and appears to have been occasionally employed by the Greeks and Egyptians for trivial, or rather for unworthy, purposes: But it is in modern times only that steam has been adapted to ends of weight or utility, and the history of the steam engine properly begins with that application.

It is not to be expected that the historical narration on which we are about to enter should contain much that is new. The facts with which we must necessarily deal have often been stated before, and we believe now admit neither of much increase nor modification; but it is not impossible, we think, to set these facts in truer lights, and to deduce from them sounder conclusions than have yet been realised. It appears to us to be a vice of many commentators, that they have attached too much importance to the deeds of individual projectors, and have estimated at far too low a rate the current intelligence of the time, of which indeed the proficiency of those exalted persons is to be regarded as merely the exponent. They have set down the early progress of the steam engine as due altogether to the perspicacity and contrivance of a few solitary adventurers, without hinting that some part of it might reasonably be ascribed to that spread of information and general advancement of knowledge to which that progress is in truth mainly attributable. The consequence of this fault is, that a host of projectors are made to shine aloft like stars,' whose merit, when tested by the general information of their own time, fades into insignificance. They stand, it is true, in the van of improvement, but the elevation due to the existing state of society is measured as a part of their intellectual stature; and while they are each presented to the imagination like a precipice starting abruptly to the skies in solitary and awful majesty, they are in truth only to be regarded as so many heights, which, whatever be their absolute altitude, rise only a few feet above the other heights around them. It is

absurd, therefore, to seek to elevate any of the early projectors of the steam engine into greatness, for they were one and all persons of only ordinary intelligence and assiduity, of which every age has produced its thousands; and the progress they made was owing rather to the natural flow of events than to any great genius or foresight on the part of any one of them. It is still more idle to set down any one of these persons as the inventor of the steam engine. Great inventions are necessarily of a slow growth, and are rarely the produce of individual minds, but require time and experience as well as ingenuity to bring them to maturity, and indeed the happiest steps are sometimes the effect of accident. In the intellectual as in the material world, the most precious productions are those which cannot spring to perfection at once, and it would be as reasonable to inquire to what refreshing shower, or to what gleam of sunshine, the stature of a stately oak is attributable, as to what individual mind we are indebted for the creation of our modern steam engine. The exertions of different minds are merely so many agencies that have been happily conducive to a great result; and it would be as just to assign the invention of our modern men-of-war to Jason, as to assign the invention of the steam engine to Savery or De Caus.

But whatever be the merit that is due to these 'sons of notoriety,' it is we think divisible only among those of them who have been instrumental in working out some practically useful result. The mere men of speculation, who have suggested modes of doing things, but have never done them, are not to be ranked with those who have really accomplished something, in a case where the whole difficulty of the task lies in its practical achievement. Whatever else these ingenious persons may be, they are certainly not among the number of the improvers of the steam engine; and their claims, if to be considered at all, ought in strictness to be considered as the claims of a distinct class of persons. Nor can the merit of such a class, under ordinary circumstances, be considerable, for there is nothing more easy than to originate vague ideas of improvement, though it is generally a very difficult thing to carry those ideas into successful practice. M. Arago, however, and his followers it seems, have set the steam engine down as a French invention, because Solomon de Caus first adopted the idea of steam as a motive force, and Papin suggested the application of the cylinder and piston. It would be as reasonable, in our apprehension, to set down the battle of Waterloo as a French victory, because Napoleon adopted the idea of fighting it; for the question in all such cases is, not who first adopted an ideal result, but who actually realised that result in practice. The scheme of Solomon de Caus was neither useful nor new, and Papin's project was so impracticable, that he himself abandoned it in favour of Savery's scheme. We have no evidence that either of those persons ever completed an engine of any kind. Papin's scheme, as he first proposed it, was worse than the previous project of the Marquis of Worcester, for it was without a boiler; and after several gyrations he certainly left the steam engine in as imperfect a state as if he had never meddled with the subject. If, therefore, we were disposed to retort upon M. Arago his pitiful nationality, we might with some plausibility say that his proofs only show the lamentable barrenness of the French intellect; for the very ideas which, in the minds of Englishmen, have quickly grown up to a rich maturity, and have blessed all nations with countless new enjoyments, have, when implanted in the minds of Frenchmen, invariably failed to produce any useful result. But this is idle. The steam engine happens, no doubt, to be from first to last an English invention; but that result, we conceive, is not so much to be attributed to the superior genius of the English people as to the force of circumstances, which made some such instrument as the steam engine more valuable to England than to other nations. If France had possessed valuable mines lying under water, and at the same time an abundance of coal ready to be made instrumental for their recovery, there is every reason to suppose that the steam engine would have been a French invention; and we think the consideration that our honours are the result merely of accident, ought to reconcile that ingenious people to a priority it is idle to contest. No nation can be expected to excel another nation of equal power and intelligence in every thing; and if it be the fact, as we willingly admit, that the French excel us in some things, they must be content to give us the palm in others, one of which certainly is steam engineering.-There is no end, however, of these speculations, and we fear they are neither very captivating nor very convincing; so that we shall here cut them short, and proceed without further preamble to the history of the invention. B

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 pneumatic 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 Pneumatica, 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 wine 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 in 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 Æolipile, 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 primum mobile, in order that the inciting power may be invisible. There is no doubt that pneumatical 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 sunrise, 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 work of Hero attracted earnest attention, and several translations of it were made which afforded an early exercise to the infant art of printing. A knowledge of the expedients of the ancient mechanicians was thus widely diffused, and it was probably one of them that was reproduced in Spain in 1543 by Blasco de Garay, a sea-captain, for the propulsion of vessels. This contrivance, whatever may have been its real nature, appears to have been very effectual. Commissioners were appointed by the Emperor Charles V. to test the invention at Barcelona on the 17th of June 1543, and the result was that a ship of 200 tons burden was propelled by the machine at the rate of three miles an hour. Nothing further is known of the invention than that the vessel was propelled by paddle wheels, and that the moving force was derived from a boiler containing water, which, it was said, was liable to explode. It appears unaccountable that after the successful result realised by Garay, no further step should have been taken respecting his plan. He was rewarded by the Emperor, and promoted into a higher rank, but his ingenuity does not appear to have been ever turned to any useful account, and his scheme was never introduced into practice.

The various works on mechanics, published about the close of the sixteenth century, are full of expedients for the elevation of water similar to those of Hero, but much less refined; and Baptista Porta, in his book on Pneumatics, published at Naples in 1601, incidentally makes mention of the following contrivance, not indeed as any discovery of his own, but merely as an arrangement of convenience, in an experiment for ascertaining the relative bulks of water and steam. "Construct a box of glass or tin, having a hole at the bottom through which is introduced the neck of a flask, containing one or two ounces of water, and let the neck of the flask be so luted to the bottom of the box that there be no leakage. Near the bottom of the box let a pipe ascend, but at such a distance from the bottom as to permit the water to get out, which pipe passing through the cover is to rise a short distance above it. The box is to be filled with water by an aperture which is afterwards to be closed up, steam tight. This being done, place the flask upon the fire, and as it becomes slowly heated, the water being gradually dissolved into air will press upon the water in the box, and acting forcibly against the water which issues through the pipe, will not escape: and if we continue the heat, the whole of the water subjected to it will be evaporated, and during such evaporation the air will constantly press upon the water in the box, and the water will constantly spring from it." A similar arrangement is mentioned in a work by Solomon de Caus, a native of Normandy, or at all events a Frenchman; not for the philosophical purpose mentioned by Porta, but merely as an illustration that water might be raised above its level by fire, a truth known from the remotest antiquity. The work of De Caus, to which we have referred, is entitled Les Raisons des Forces Mouvantes avec diverses Machines tant utiles que plaisantes, Paris, 1623. This work is dated Heidelberg, 1615, and the first edition appears to have been published at Frankfort: it contains the following among several other theorems of equal insignificance:-" Take a ball of copper well soldered at every part; it must have a vent-hole to put in the water, and also a tube which is soldered to the top of the ball, the end of which ap proaches near to the bottom of the ball without touching it. After filling this ball with water through the vent-hole, stop it close and put it on the fire; then the heat striking against the ball will cause all the water to pass through the tube." De Caus also mentions a scheme of a solar fountain, but it, as well as the preceding, are merely clumsy imitations of some of the 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 diameter, and one inch thick, which being filled with water by a small hole subsequently stopped by a peg, so that neither air nor water can escape, it is certain that if the said ball be put over a great fire so that it may become very hot, it will cause so violent a compression, that the ball will be shattered in pieces." The great force of steam, however, was very well known to the ancients, who even went the length of ascribing earthquakes to pent up vapours, generated by subterranean heat; and for ages the lime burners of Italy had been obliged to be careful of introducing hollow limestones into their kilns, as the water within them, when converted by the heat into steam, caused dangerous explosions. M. Arago, however, tells us that the ideas of the ancients respecting the force of steam had never reached any thing like the numerical appreciation realised by such experiments as those of De Caus. We confess that we are at a loss to understand wherein this numerical appreciation can consist, for although De Caus or Rivault may have ascertained that steam will burst a certain ball or bomb, they never ascertained what sort of ball or bomb steam will not burst, so that they did not establish any limit to the power of steam, but only showed that it is capable of very powerful effects. This, however, was known long previously; and in attributing to the force of pent up steam even such stupendous com. motions as earthquakes—the upraising of continents and rending asunder of mountains-the ancients must have had at least quite as magnificent ideas of the force of that mighty agent as is to be afforded by the bursting of a ball or bomb, and we cannot perceive in what way an experiment establishe any thing which only proves that the power of an agent is adequate to the production of effects far more paltry than are known to be within the range of its capacity.

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

Preliminary Discourse.

si tanto spiritali quanto di animale operatione. This contrivance consists of a wheel furnished with boards set round its periphery, after the manner of an undershot water wheel, against which a jet of steam proceeding from a boiler is made to impinge, thereby forcing the wheel into revolution. An engine on this plan would necessarily be very ineffectual, and would indeed be greatly inferior to the Æolipile of Hero, for although it is undoubtedly the fact that the power of steam issuing from an orifice is expended in giving velocity to its own particles, and ought therefore, theoretically speaking, to be again surrendered by those particles during impact, yet this result cannot be realised in practice, and the great velocity at which the wheel requires to travel, makes the scheme perilous and impossible. Mr. Pilbrow, however, has during the past year revived this species of engine, and has taken out a patent for the particular arrangement he proposes. His engine is described and delineated in the first volume of THE ARTIZAN, and the causes are there pointed out, with considerable fulness of detail, which must prohibit its success.

The whole of the contrivances we have hitherto enumerated are mere mechanical toys, and although not incapable of useful applications, they appear only to have been employed to excite the wonder of the ignorant, and were never used for any serious purpose. To this judgment indeed the machinery of Blasco de Garay is an exception, for in that case, if the reports which have reached us may be relied upon, a useful result was undoubtedly realised. Yet this result contributed nothing to the success subsequently reached, and is rather an episode in the history of steam improvement, than a link in the chain of progress. The trial of De Garay's machinery indeed was a mere experiment, a successful one it is true, but one nevertheless which was barren in its effects, for in a few years all recollection of the achievement had become obliterated, and the contrivance, whatever might be its merits, was certainly never reduced to successful practice. It appears extremely probable that the machinery employed by De Garay was merely the ancient Eolipile on a superior scale of magnitude, for the low state of the mechanical arts in his time, and the small mechanical refinement to be expected of a sea-captain, equally discourage the idea that he should have reached any very exquisite or difficult kind of mechanism. It is idle, however, to speculate on such a subject, and we must therefore rest content with the certainty that the scheme of this enterprising person was never brought into practice, and that up to the epoch at which we have now arrived no useful application of steam power to the purposes of life had been accomplished.

The next name on our list is the Marquis of Worcester, who in 1663 published a pamphlet addressed to King Charles II. and the English Parliament, entitled "A Century of the Names and Scantlings of the Marquis of Worcester's Inventions," with the view to obtain the aid of government for their prosecution. Among many ingenious and some fantastic and preposterous devices, we have the following fire water-work, "An admirable and most forcible way to drive up water by fire; not by drawing or sucking it upwards, for that must be as the philosopher calleth it 'infra sphæram activitatis,' which is but at such a distance, but this way hath no bounder if the vessel be strong enough; for I have taken a piece of whole cannon, whereof the end was burst, and filled it three quarters full of water, stopping and screwing up the open end, as also the touch-hole, and making a constant fire under it; within twenty-four hours it burst, and made a great crack, so that having a way to make my vessels so that they are strengthened by the force within them, and the one to fill after the other, I have seen the water run like a constant fountain stream, forty feet high. One vessel of water rarefied by fire driveth up forty of cold water, and a man that tends the work has but to turn two cocks that one vessel of water being consumed another begins to force and re-fill with cold water, and so successively; the fire being tended and kept constant, which the self-same person may likewise abundantly perform in the interim between the necessity of turning the said cocks."

This is the first feasible scheme for raising water by steam power that history records, and it is in that application that the modern steam engine had its origin. Previous projectors had in no way improved upon the expedients described by Hero, and indeed in by far the majority of cases the movement had been retrograde; but in the Marquis of Worcester's contrivance we have an engine of respectable efficacy applied to a weighty purpose, and from his time the progress onward has never been interrupted, but improvement has followed upon improvement, until the steam-engine has become what we now find it. It is idle to say that the Marquis of Worcester's project was only a reproduction of that of De Caus. The instrument of De Caus was a mere toy, not intended, and certainly not adapted for any purpose of practical utility, whereas the Marquis of Worcester enumerates many important practical uses, to which his engine might be applied, and many of them it certainly would have been perfectly competent to compass. In another part of his Century he says that his water work "is by many years' experience and labour so advantageously by me contrived, that a child's force bringeth up an hundred foot high, an incredible quantity of water, even two foot diameter, so naturally, that the work will not be heard into the next room, and with so great ease and geometrical symmetry, though it work day and night from one end of the year to the other, it will not require forty shillings' reparation to the whole engine, nor hinder one day's work, and not only with little charge to drain all sorts of mines, and furnish cities with water though never so high seated, as well as to keep them sweet, running through several streets, and so performing

the work of scavengers, as well as furnishing the inhabitants with sufficient water for their private occasions."

It appears very clear from these descriptions that the Marquis of Worcester not only had succeeded in making a powerful and effective engine, but had arrived at a very just conception of the important ends such a machine may be made to fulfil. None of the contrivances before his time were provided with means to make their action continuous, and the instrument of De Caus, so far from being adapted to raise water from a mine, or for the supply of towns, had merely the power of emptying itself of the boiling water with which it was filled. Indeed, it appears undeniable that the Marquis of Worcester was the first person, so far as our present knowledge extends, by whom "a water-commanding engine" of any power or utility was constructed, and he seems to have brought his contrivance to nearly all the perfection of which that species of engine is susceptible. There is no evidence that he made use of the atmospheric pressure as an aid to the final effect, but he seems perfectly conscious of the applicability of that agency, and indeed speaks as if such an application was very well understood in his time. We are not aware that there is any drawing extant of this machine; and the various hypothetical delineations of it that we have seen err, we think, in representing it as provided with only one boiler, for there could not in this kind of engine have been any feedpump, and in the absence of that instrument two boilers must have been indispensable to make the action of the engine continuous. Besides the description says, that "one vessel of water being consumed another begins to force, and refill with cold water," which we take to mean that when the water of one boiler was evaporated it was filled up with cold water, and the other was in the meanwhile put into operation; the water in the boiler last filled having again become hot before that in the other was exhausted. One of these engines appears to have been set up to draw water out of the Thames at Vauxhall, and is thus spoken of by Cosmo de Medici, who inspected it in 1653. "It raises water more than 40 geometrical feet by the power of one man only, and in a very short space of time will draw up four vessels of water through a tube or channel not more than a span in width, on which account it is considered to be of greater service to the public than the other machine near Somerset House," which last was one driven by two horses. We should be disposed to infer from this account, that the principle of the atmospheric pressure was employed in this engine, for it is difficult to see by what power, other than suction, the necessary rapidity of motion could be given to the water in the pipe leading from the river to the engine, and which would appear to be smaller than the pipes applied in other cases.

We have now, then, brought the history of the steam engine down to the point at which its application to purposes of utility begins, and we believe most of our readers will concur with us in the opinion that the Marquis of Worcester's "water-commanding engine" was the first machine moved by fire of efficacy and permanence. To it, indeed, the pedigree of the modern steam engine is easily traceable, while between the epochs of Lord Worcester and of Hero nothing appears to have been contrived of novelty or merit in this department of ingenuity. We are not disposed, however, to attach any great merit even to Lord Worcester's contrivance, for it is deducible, without any great stretch of the imagination, from the schemes of Hero; and indeed there is very little doubt that the ancients would have realised a very effectual steam engine if they only had possessed mines that required to be drained, and coal to bestow on such a purpose. It is to the force of circumstances chiefly that the superior proficiency of the present age in such devices is to be ascribed; and we hold it vicious in principle to confound this impelling power with the ingenuity appertaining to particular inventors, and which nature dispenses with wonderful uniformity to all generations.

FROM THE INTRODUCTION OF THE FIRST USEFUL STEAM ENGINE TO THE APPLICATION OF THE PRINCIPLE OF A VACUUM.

We have already hinted our belief that the method of raising water by the action of the vacuum, or to speak more properly, by the atmospheric pressure, was not unknown to the Marquis of Worcester, and that in one of his engines erected at Vauxhall that agency was probably employed. We have no proof, however, that such was the case; and in the description of his engine in the "Century of Inventions," he certainly disclaims the use of a vacuum, at least as a chief agent. In the engine of Captain Savery, however, of which we must now say something, the plan of a vacuum is introduced with much effect, and instead of the water in his engine being forced up all the way by steam pressure, the receivers, or forcing vessels, are situated thirty feet above the level of the water, to which height the water is drawn by the vacuum created within them. As the principle of the atmospheric pressure is one which bears much upon this inquiry, it may be worth while to say a few words respecting it.

It was maintained by the greater number of the ancient philosophers that the existence of a vacuum was impossible, and was abhorrent to nature. Galileo was the first to suspect that the horror attributed to nature was imaginary, or was at least confined within limits of no very wide range, for on the application of a pump to a very deep well sunk by the Grand Duke of Tuscany at Florence, it was found that the water would not rise more than thirty-two feet, leaving the upper part of the pipe empty, from which Galileo inferred that nature's horror of a vacuum

did not extend beyond the antipathy of thirty-two feet of water. The speculations of Galileo were prosecuted after his death by his pupil Torricelli, who, in 1643, discovered that the effort of any fluid open to the atmosphere to enter a vacuous space is owing to the pressure of the air upon bodies on the earth's surface. This discovery gave a great impulse to mechanical ingenuity, and many schemes were contrived to make this new agent available as a motive power; but the first of these projects that appears to have been of any avail was the fire engine of Captain Thomas Savery, who produced a vacuum by condensing steam in close vessels, and then applied the vacuum so obtained to the elevation of water. Savery, however, also made use of the elastic force of the steam after the manner proposed by the Marquis of Worcester; but he made the pressure of the atmosphere carry the water up the first stage, which the Marquis of Worcester does not appear to have done, although there must have been a vacuum created in his receivers as effectually as in those of Savery, occasioned by the condensation of the steam on the entrance of the cold water. Savery obtained a patent from William III. "for raising water, and occasioning motion to all sorts of mill-work by the impellent force of fire" in 1698; and for several years thereafter he appears to have been actively engaged in getting his engine introduced into practice. In 1702 he published a small work, called the "Miner's Friend," in which he gives the following account of the structure of his engine, and of the mode of its operation :

"AA the furnaces which contain the boilers; B1, B2 the two fire-places; C the funnel, or chimney, which is common to both furnaces. In these two furnaces are placed two vessels of copper, which I call boilers, the one large, as L, the other small, as D; D the small boiler contained in the furnace, which is heated by the fire at B 2; E the pipe and cock to admit cold water into the small boiler to fill it; F the screw that covers and confines the cock E to the top of the small boiler; G a small gauge cock at the top of a pipe, going within eight inches of the bottom of the small boiler; H a

larger pipe, which goes the same depth into the small boiler; I a clack or valve at the top of the pipe H (opening upwards); K a pipe going from the box above the said clack or valve, in the great boiler, and passing about an inch into it; LL the great boiler contained in the other furnace, which is heated by the fire at B1; M, the screw with the regulator, which is moved by the handle Z, and opens or shuts the apertures at which the steam passes out of the great boiler into the steam-pipes 00; N a small gauge cock at the top of a pipe which goes half way down into the great boiler; 01, 02, steam-pipes, one end of each screwed to the regulator, the other ends to the receivers PP, to convey the steam from the great boiler into those receivers; P1, P2, copper vessels called receivers, which are to receive the water which is to be raised; Q screw joints, by which the branches of the water-pipes are connected with the lower parts of the receivers; R 1, 2, 3, and 4, valves or clacks of brass in the water-pipes, two above the branches Q, and two below them; they allow the water to pass upwards through the pipes, but prevent its descent; there are screw plugs to take out on occasion, to get at the valves R; S the forcing-pipe which conveys the water upwards to its place of delivery, when it is forced out from the receivers by the impellent steam; T the sucking-pipe, which conveys the water up from the bottom of the pit, to fill the receivers by suction; V a square frame of wood, or a box, with holes round its bottom in the water, to enclose the lower end of the sucking-pipe, to keep away dirt and obstructions; X a cistern with a buoy-cock coming from the force-pipe, so as it shall always be kept filled with cold water; Y Y a cock and pipe coming from the bottom of the said cistern, with a spout to let the cold water run down on the outside of either of the receivers P P; Z the handle of the regulator, to move it by, either open or shut, so as to let the steam out of the great boiler into either of the receivers.

The Manner of working the Engine.

"The first thing is to fix the two boilers of the engine in a good double furnace, so contrived that the flame of the fire may circulate round, and encompass the boilers to the best advantage, as you do coppers for brewing. Before you make any fire, unscrew the two small gauge-pipes, and cocks, G and N, belonging to the two boilers, and at the holes, fill the great boiler L two-thirds full of water, and the small boiler D quite full; then screw in the said pipes again as fast and tight as possible, and light the fire under the large boiler at B 1, to make the water therein boil, and the steam of it being quite confined must become wonderfully compressed, and therefore will, on the opening of a way for it to issue out (which is done by pushing the handle Z of the regulator as far as it will go from you), rush with a great force through the steam pipe O 1, into the receiver P 1, driving out all the air before it, and forcing it up through the clack R 1, into the forcepipe, as you will perceive by the noise and rattling of that clack; and, when all the air is thus driven out, the receiver P1 will be very much heated by the steam. When you find it is thoroughly emptied, and is grown very hot, as you may both see and feel, then pull the handle Z of the regulator towards you, by which means you will stop the steam pipe O 1, so that no more steam can come into the receiver P 1, but you will open a way for it to pass through the other steam pipe O2, and by tha means fill the other receiver P 2 with the hot steam, until that vessel has discharged its air through the clack R 2 up the force pipe, as the other vessel did before.

"While this is doing, let some cold water be poured on the first-mentioned receiver P 1, from the spout Y, by which means the steam in it being cooled and condensed, and contracted into a very little room, a vacuum or emptiness is created, and consequently the steam pressing but very little (if at all) on the clack R 3 at the bottom of the receiver P 1, there is nothing there to counterbalance the pressure of the atmosphere on the surface of the water at the lower part V of the sucking-pipe T, wherefore the water will be pressed np, and ascend into and fill the receiver P 1, by what is commonly called suction: the water as it rises lifts up the clack or valve R 3, which afterwards falling down again and shutting close, hinders the descent of the water that way.

"The receiver P 2 being by this time emptied of its air, push the handle of the regulator from you again, and the force of the steam coming from the great boiler will be again admitted through Q1, and will act upon the surface of the water contained in the receiver P1; which surface only being heated by the steam, it does not condense it, but the steam gravitates or presses with an elastic quality like air, and still increasing its elasticity or spring until it counterpoises, or rather exceeds the weight of the column of water in the receiver and pipe S, which it will then necessarily drive up through the passage Q R 1 into the force-pipe S. The steam takes up some time to recover its power, but it will at last discharge the water out at the top of the force-pipe S, as it is represented in fig. 3. After the same maner, though alternately, the receiver P 2 is filled with water by means of the suction, and then emptied by the impellent force of the steam, whereby a regular stream is kept continually running out at top of the force-pipe S, and so the water is raised very easily from the bottom of the mine, &c. to the place where it is designed to be discharged. I should add, that after the engine begins to work, and the water is risen into and hath filled the force-pipe S, then it also fills the little cistern X, and by that means supplies the spout or pipe Y Y, which I call the condensing pipe, and which by its handle can be turned sideways over either of the

receivers, and is then open; by this spout cold water is conveyed down from the force-pipe to fall upon the outside of either of the receivers when thoroughly heated by the steam, in order to cool and condense the steam within, and make it suck (as it is usually called) the water out of the well up into that receiver.

"It is easy for any one, that never saw the engine, after half an hour's experience, to keep a constant stream; for on the outside of the receiver you may see how the water goes out as well as if the receiver were transparent for as far as the steam continues within the receiver, so far is that vessel dry without, and so very hot as scarce to endure the least touch of the hand; but as far as the water is withinside of the said vessel, it will be cold and wet on the outside where any water has fallen on it; which cold and moisture vanish as fast as the steam in its descent takes place of the water. But if you force all the water out of the receiver, the steam, or a small part thereof, will go through the clack R 1 or R 2, and will rattle that clack so as to give notice to move the handle of the regulator, and then the steam begins to force out the water from the other receiver P, without the least alteration of the stream, only sometimes the stream will be rather stronger than before, if you pull the handle before any considerable quantity of steam be got up the clack R: but it is much better to let none of that steam go off, for that is but losing so much strength, and it is easily prevented by pulling the regulator some little time before that receiver which is forcing is quite emptied.

"This being done, turn the cock, or condensing pipe Y of the cistern X, over the empty receiver, so that the cold water proceeding from X may run down through Y, which is never opened but when turned over one of the receivers, but when it stands between them is tight and stanch. This cold water falling on the outside of the receiver, by its coolness causes that steam which had such great force just before, to condense and become an empty space, so that the receiver is immediately refilled by the external pressure of the atmosphere, or what is vulgarly called suction, whilst the other receiver is emptying by the impellent force of the steam, which being done, you push the handle of the regulator from you, and thus throw the force into the other receiver, pulling the condensing pipe over the receiver P 2, causing the steam in that vessel to condense, so that it fills while the other empties—the labour of turning these two parts of the engine, viz. the regulator and condensing water-cock, and tending the fire, being no more than what a boy's strength can perform for a day together, and is as easily learned as their driving of a horse in a tubgin. Yet after all, I would have men employed in working of the engine, and those too the most apprehensive, supposing them more careful than boys: the difference of this charge is not to be mentioned when we consider the vast profit which those who use this engine will reap by it.

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"The ingenuous reader will here probably object, that the steam being the cause of this motion and force, and that as steam is but water rarefied, the boiler L must in some certain time be emptied, so as the work of the engine must stop to replenish the boiler, or endanger the burning out or melting the bottom of the boiler. To answer which, please to observe the use of the small boiler D; it is supplied with water from the force-pipe by a small pipe and cock E; when it is thought fit by the person tending the engine to replenish the great boiler (which requires about an hour and a half or two hours' time to the sinking one foot of water), he turns the cock E, so that there can be no communication between the force pipe S, and the small boiler D, and putting in a little fire under the small boiler at B 2 the water will there grow presently hot, and when it boils, its own steam, which hath no vent out, will gain more strength than the steam in the great boiler. For the force of the great boiler being perpetually spending and going out, and the other confined and increasing, it is not long before the force in the small boiler exceeds that in the great one; so that the water in the small boiler being depressed by its own steam pressing on its surface, will force the water up the pipe H, through K, into the great boiler L; and so long will it run till the surface of the water in the small boiler D gets to be as low as the bottom of the pipe H, and then the steam and water will run together, and by its noise and rattling of the clack I, will give sufficient assurance to him that works the engine that the small boiler hath emptied and discharged itself into the greater one L, and carried in as much water as is then necessary; after which, by turning the cock E again, you may let fresh cold water out of the force-pipe S into the lesser boiler D, as before, and thus there will be a constant motion and a continual supply of the engine, without fear of decay or disorder. And inasmuch as from the top of the small boiler D to the bottom of its pipe H (which is within eight inches of the bottom of the boiler) there is contained about as much water as will replenish the great boiler L one foot, so you may be certain it is replenished one foot of course.

"Also, to know when the great boiler wants replenishing or not, you need only turn the gauge-cock N, and if water come out there is no need to replenish it, but if steam only come, you may conclude there is want of water; and the like will the cock G do in reference to the small boiler D, showing when it is necessary to supply that with fresh water from S, so that in working the engine there is very little skill or labour required; it is only to be injured by either a stupid or wilful neglect.

"And if a master is suspicious of the design of a servant to do mischief, it is easily discovered by those gauge-pipes; for if he come when the engine is at work, and find the surface of the water in the great boiler L below the bottom of the gauge-pipe N, or the water in the small boiler D below the

bottom of the gauge-pipe G, such a servant deserves correction, though three hours after that, the working on, would not damage or exhaust the boilers. In a word, the clacks being, in all water-works, always found the better the longer they are used, and all the moving parts of our engine being of like nature, the furnace being made of Sturbridge or Windsor brick or firestone, I do not see it possible for the engine to decay in many years, for the clacks, buckets, and mitre-pipes, regulator and cocks, are all brass; and the vessels made of the best hammered copper, of sufficient thickness to sustain the force of the working of the engine. In short, the engine is so naturally adapted to perform what is required, that even those of the most ordinary and meanest capacity may work it for some years without any injury."

A good many of these engines appear to have been constructed and set to work. They were not employed, however, in any case in which water had to be lifted from a great depth, as the great pressure of steam requisite to overcome the gravity of a high column of water was reckoned inconvenient and dangerous in those days of fragile boilers and imperfect workmanship. These disadvantages appear to have been the chief cause of the relinquishment of Savery's engine in favour of that of Newcomen; for in the early career of Newcomen's contrivance the useful effect under certain circumstances was inferior to that of the engine it superseded, and the first expense was greater: but then Newcomen's plan made the column of water that could be lifted independent of the pressure of the steam, an increase in the height of the column only requiring an increase in the diameter of the cylinder. The details of Savery's contrivance are extremely judicious, and the scheme altogether speaks very favourably of his ingenuity and perseverance. It has been a matter of controversy whether he invented the engine altogether himself, or borrowed the idea from the Marquis of Worcester, and merely matured the plan of that noble mechanic. Desaguliers retails an idle story of Savery buying up the Marquis of Worcester's book in Paternoster Row and destroying it, so that the priority of the Marquis might remain unknown; but we give very little credit to the tale. There were probably at the time some of the Marquis's engines in being, which would be a much more conclusive testimony than any book could be, and at least there must have been many persons then living who recollected the engine set up by the Marquis at Vauxhall. Besides, the very act of buying up a book which had been many years in circulation, or rather of attempting to buy it up, would be the surest way to attract attention towards it, and thus produce the very disclosure it was Savery's imputed object to avert. We think it likely enough that Savery may have invented this engine entirely himself, without knowing anything of what the Marquis of Worcester had done forty years before, although in the pursuit of the subject he must of course have become acquainted with the achievements of his predecessor. The same wants generate so naturally the same expedients for their relief, that simultaneous discoveries and inventions become inevitable, and identical projects start up at different epochs without imitation, under the force of similar circumstances. The ingenuity, too, displayed by Savery in the details of his engine encourages the idea that it may have been altogether of his own contrivance, for he does not appear to have been unequal to such a performance, which indeed it did not require any very brilliant genius to accomplish. But whatever conclusion may be come to upon this head, we are at least certain that it was Savery who first introduced the fire-engine into extended use; and he prosecuted his undertaking with great assiduity and success; though, as he says, he "was obliged to encounter the oddest and almost insuperable difficulties," and at a great expenditure of energy and means. The merit of this achievement is in our apprehension much greater than that of the mere invention of the machine; for such a work is one of equal difficulty, and of infinite toil and discouragement, and is little lightened by the bright dreams of fancy or the consolations of applause.

FROM THE APPLICATION OF THE PRINCIPLE OF ATMOSPHERIC PRESSURE TO THE INTRODUCTION OF THE CYLINDER.

About seven years after the discovery of the pressure of the atmosphere. by Torricelli, Otto Guericke, a magistrate of Magdeburgh, without any knowledge of what Torricelli had done, succeeded in obtaining a vacuum in a cask by means of an air pump, and contrived a great variety of ingenious pneumatic apparatus; some for raising water in a pipe by means of an exhausted receiver screwed on the top, and others for lifting a great weight by means of a cylinder fitted with a piston, beneath which was a vacuum, while the atmosphere pressed on its superior surface. The nature of the arrangement he adopted in this latter case will be at once apprehended by a reference to the annexed figure, where A is a cylinder fitted with a piston, to the shank of which a rope is attached, passing over the pullies B and C with a scale D hung at its extremity loaded heavily with weights. A small pump was screwed into the lower part of the cylinder, by means of which the cylinder was exhausted, and the piston descending raised the weights.

We have in these ingenious devices the same mechanical arrangements as those afterwards employed by Savery and Papin in their projects; and indeed the only material difference between the cylinder apparatus here represented and the atmospheric steam engine is that in the one case the vacuum is produced by means of a pump, and in the other by the condensation of steam. It is in the production of a vacuum, therefore, by the