The Great Invention and its Predecessors
"As the Births of Living Creatures, at first, are ill-shapen, 80 are all Innovations, which are the births of Time."BACON.
MAN has always been observant, inquisitive, and lazy; and he has,through life, a child's passion for toys. Consequently, when the Creator set man, fire, and water in the world together, it was evident that ultimately the steamengine would have its place among the births of Time. The first steps towards its invention are blurred and unrecognisable, for there are no periods in the infancy of thought. That benefactor of humanity who first boiled water in a vessel remains unknown. We must hurry down the ages to a point where time has measurable length, and the features of history take shape before us, as the sleepers between the rails detach themselves into an expanding series as the eye travels home along the track from the farthest limit of vision to the ground at our feet. Man is beginning to play with this new element. He has discovered that it has force and that with its help he can make toys that work. Heat water in the hollow hub of a wheel, and the steam, driven along the radiating tubes that are the spokes, will issue violently from the nozzles of those spouts, all bent one way, and drive it spinning as a catherine-wheel is driven. Or make a hollow doll of brass, with a hole for his mouth, fill him with water and set him by the fire. As the water boils, the steam will issue in a strong, steady blast from his mouth, and he will seem to blow the fire that heats him.
From 200 B.C. to A.D. I600 steam was little more than a toy; then the laziness of man prompted him to use this force to ease his labour. It is said that a Spaniard drove a boat by steam in I543~~ but, as nobody knows how he did it, we pass on to Solomon De Caus. He was an engineer and architect to Louis XIII of France, who came to England in I6I2 and was employed by the Prince of Wales to embellish his gardens at Richmond. He invented means for raising water above the height of its source and so constructing ornamental falls and fountains. One method was by the use of fire. He took a metal globe and partly filled it with water through a cock, which was then closed. Through the top of the globe he inserted a vertical pipe, the lower end of which came down nearly to the bottom of his globe and was therefore under the water. Then he applied the fire. The heated air and steam pressed on the surface of the water in the vessel and forced it to escape by the only way open to it, namely, up the pipe and out as a jet from the top. The result was a toy fountain. It was of no practical use, and could hardly be called an engine, but it is worth describing as being the simplest example of one of the methods of raising water with the aid of fire.
The next claimant to a place on the roll of inventors is Edward Somerset, Marquis of Worcester. He was altogether a fantastic character. Having acted as Charles I's agent in some of his wildest schemes during the Civil War, he escaped to France. But he got tired of life abroad, and, although he had been condemned to death in his absence, he returned to England. Whether it was the calm assurance of the man, or the memory of his reputation for fabulous wealth, or some irresistible magnetism in his personality, it is impossible to say, but instead of being immediately put to death he was sent to the Tower, and after two years released with a pension. It was at this time that he wrote his amazing book, entitled X Century of the Names and Scantlings of the Marquis of Worcester's Inventions, which he published after the Restoration with an effusive dedication to Charles II, in which he offered it to his King as an indication of the ways in which he might still be of service to him.
At the first glance it appears to be the work of a lunatic. Closer study shows that the Marquis had simply collected every ingenious device he had ever met with in life, literature or legend, and boldly claimed that he possessed the secret of each without venturing to explain what that secret was. This type of invention is impressive without being difficult. There are several shorthand alphabets and codes, several portable fortifications and repeating pistols, a watch that goes for ever, a perpetual motion, a torpedo, an " artificial bird," " a most conceited tinder box," and an automatic horse that a man may ride " using the decent posture with bon grace." King Charles is told by this unemployed commander of royalist armies and negotiator of secret treaties how he may make a head of brass or stone, which, if he whispers a question in its ear, " will presently open its mouth, and resolve the question in French, Latin, Welsh, Irish or English, in good terms uttering it out of his mouth, and then shutting it until the next question be asked." Among these marvels are some machines for raising water, mostly by buckets working over wheels and pulleys. Two of these are interesting, Number 68 called " A Fire WaterWork," and Number I00 modestly described by its author as " the most stupendious work in the whole world." Number 68 was clearly a steamengine on the principle of De Caus, only differing from his in that it had a separate boiler for generating the steam. Number I00 is not clearly enough described to be reconstructed, but it seems to have been some kind of water-wheel worked by a man whose strength was multiplied by a system of weights and pulleys. Now it is known that a water-engine was set up by the Marquis at Vauxhall; several people report having seen it. Was it Number 68? If so, the Marquis had turned De Caus's toy into a fullsized steam-engine of practical value. Unfortunately none of those who saw it make any mention of the use of fire; their descriptions suggest that it was not a steamengine at all, but the quite unoriginal and unimportant Number I00. This last of the century, though the least ingenious of the collection, was the inventor's chief pride, the darling of his heart. Was this because it was the only one of the hundred that ever materialised ? It seems highly probable; and the Marquis of Worcester must be classed among those brilliant charlatans who never lack a train of devoted disciples.
Real progress began with the work of Dionysius Papin. He was a French doctor who fled from his country in I68I to escape the persecution of Protestants, settled in London, and became a Fellow of the Royal Society. Shortly before this a line of inquiry started by Galileo, and pursued by his pupils in Italy, had led to a very important discovery. It used to be said that " Nature abhors a vacuum." This peculiarly unscientific and almost mystic statement of the case had proved very misleading. The Italians now discovered that it was nonsense to talk as if there were special laws of nature relating to a vacuum it was simply a question of the pressure of the atmosphere. The air is exerting a continuous pressure in all directions. As it is in all directions it normally has no effect on the objects it surrounds, for the pressure is perfectly balanced. But if you can withdraw the air from one side of a body there is nothing to balance the pressure on the other. The body is therefore propelled into the vacuum with a force equal to the pressure of the atmosphere. Here was a universal, everpresent force provided by nature free of charge, constant where wind and water are fickle, and not liable, like steam, to become unruly and burst the vessels intended to contain it. And this admirable force had not yet been pressed into the service of man.
The chief obstacle to the use of atmospheric pressure to drive a machine was the difficulty of producing the vacuum. To Papin belongs the credit for having thought of employing steam to do this. He took a cylinder, open at the top like a shellcase that has been converted into a flowervase, and fitted it with a piston. He put a little water in the bottom of the cylinder, lowered the piston till it rested on the surface, and set it over a fire. As the water boiled, the piston was raised to the top, while the cylinder filled with steam. There it was locked with a catch, and the fire was removed. As the cylinder cooled, the steam was condensed and became once more a layer of water on the bottom, leaving a vacuum under the piston. When the catch was released the piston made a powerful stroke, driven down by the pressure of the atmosphere which now had no resistance to overcome. He then replaced the fire and started again. Such was Papin's engine, clumsy and desperately slow in working, but rich in suggestions for future engineers.
The scene now shifts to Devonshire. Thomas Savery was born in a village not far from Plymouth about the year I650. He was a military engineer and also a clever clockmaker. Whereas De Caus and Papin had started their investigations as scientists trying to fathom the mysteries of nature, Savery began from the other end. He had often travelled about in Cornwall, and had seen for himself the difficulties the tin miners were having in keeping their mines clear of water. The workings had reached a depth at which the old pumps ceased to function, and there was pressing need for something more powerful. Savery tackled this problem as a practical man and an engineer, and he invented an engine, patented in I698~~ which was actually introduced into some of the mines.
His method was as follows.
He filled a vessel with steam, and then, by pouring cold water over it, condensed the steam and created a vacuum. So far he wasfollowing Papin, except that he generated the steam in a separate boiler which he could keep constantly hot, whereas Papin boiled his water in the cylinder in which he condensed it, and so had to keep taking the fire away and putting it back again. That alone was a big saving. But Savery did not use a piston Having got the vacuum, he opened a pipe that communicated directly with the water to be raised, and up it rushed into his vessel. In this way he could get the water up about 30 feet. That was not enough, so he now applied De Caus's system to force it higher. He turned on the steam again, at high pressure, and it acted on the water in the vessel and drove it up and out through an ejection pipe. The remarkable thing about this engine was that it sometimes worked. Sometimes, not always. For the utmost skill of the blacksmith of those days was not equal to constructing a boiler that could be relied on to contain itself when tickled by high-pressure steam. Bursts and leakages were common, and the engineman led a perilous existence.
The fact that a steam-engine had actually been used, with some measure of success, to drain a mine was a great stimulus to further efforts, and they were quickly forthcoming. Thomas New comen, a Dartmouth blacksmith, knew what Savery was doing; he may even have been employed by him as a mechanic on his engines. He also had, with the help of Dr. Hooke of the Royal Society, studied the experiments of Papin. He either got from Hooke, or himself conceived, the idea of combining the advantages of both. Savery's machine was in itself a pump. It sucked the water up into its own bowels. Newcomen proposed to build an engine that would simply provide the power, and then to use it to drive an ordinary suction pump which would raise the water. This had been Papin's intention, but he had left the work unfinished. He airily remarked that the manner of using his engine to " dis charge iron bullets to a great distance, to propel ships against the wind," and so forth, " would be too long here to detail; but each individual must select the construction of machinery appro priate to his purpose." This is what Newcomen did. He took Papin's piston and cylinder and made it pull down one end of a beam, pivoted in the centre, to the other end of which was attached the rod of a common pump. But at the same time he applied Savery's improvement by generating the steam in a separate boiler, and leading the steam from it to the cylinder, where it was condensed by a douche of cold water. Savery complained that this was an infringement of his patent, but was pacified by being taken into partnership. The first successful model was completed in I705 and the first engine was set up at Wolverhampton in I 7 I 2.
We must now return to James Watt at Glasgow. It was in the year I759 that he first turned his attention to steam-engines. The suggestion came from Robison. He knew that steamengines were being used to pump mines and was not thinking about ways of improving them, but of possible new uses for steam. Might it not be used to drive carriages on wheels? Why not invent a steam locomotive ? Savery had had the same idea, but nobody had yet succeeded in carrying it out. It will be remembered that Robison said of Watt, " He needed only to be prompted; everything became to him the beginning of a new and serious study everything became science in his hands." Well, he had now been prompted. And Robison. was quite right. He did not play with the idea, he worked at it. He first tried, as any one would, to drive his engine by the pressure of steam itself. This seems so obvious, that people often wonder why engineers at first preferred the far more complicated and round-about way of using steam only as a means for making a vacuum, and so bringing the pressure of the atmosphere into play. The explanation is simple. If atmospheric resistance is not removed by means of a vacuum, it must be overcome by the driving. force of the steam. The steam must be used at high pressure. Now in the eighteenth century mechanical technique was not good enough either to produce a steady supply of high-pressure steam, or to contain or control it if produced. Watt, therefore, like his predecessors, soon gave up his attempt to devise a high-pressure engine, because he was " sensible it would be liable to some of the objections against Savery's engine, viz. the danger of bursting the boiler, and the difficulty of making the joints tight."
In later years Watt would never have begun to experiment on a problem until he had studied and mastered everything that had been done or written on the subject by any one before him. Even now he soon checked his hasty enthusiasm and sat down to complete his education. He read a few standard works. Then he wanted to see an example of the latest type of engine in use. He discovered that the University possessed a model of a Newcomen engine, but that it was at the moment in London, undergoing repairs. It was probably at Watt's suggestion that Professor Anderson recovered this model from London and handed it over to him to be put into working order. This was in the winter of I763. At first he was not thinking of theories. " I set about repairing it," he says, " as a mere mechanician." But when he had finished, although the model was mechanically as perfect as any fullsized engine, it would only make two or three strokes at a time, and then expired. Here was a puzzle of a new kind. It led him away from the purely mechanical aspects of the problem; it " became science in his hands." He saw that heat was being wasted. In the big engines the cylinder was made of castiron; in the model it was of brass, a better conductor of heat. Therefore energy was going astray, as it were, in heating the cylinder. He saw that the toy cylinder " exposed a greater surface to condense the steam in proportion to its content " than a big cylinder. Therefore, when the cold cylinder was being filled with steam, a great deal was uselessly turned to water. From this he saw that the model was more wasteful than a real engine. But he also saw, and this is much more important, that even in a full-sized engine with a perfectly proportioned cylinder of the most suitable material known to exist there would still be waste of energy and loss of power, arising from the very principle on which the machine worked. He determined to find out what that waste amounted to. In doing this he was led into a series of elaborate scientific experiments on the nature of heat and the properties of steam.
Three aspects of the problem occupied him. It had already been shown by experiment that, when subjected to a pressure lower than that of the atmosphere, water would boil at a temperature lower than the ordinary boilingpoint. Watt carefully worked out a scale showing at what temperature water will boil at every pressure from nil upwards. In his neat, precise way, he reduced a general theory to an exact, quantitative form. Then he went on to discover the relation between the volume of a given quantity of water and the volume of steam, at the temperature of boiling water, into which it could be converted. Others had tried to do this before, but Watt's researches proved that their conclusions were at fault. His scientific mind, aided by his mechanical genius for experiment, enabled him to get results that far surpassed in accuracy anything that had been done before. Finally he was struck by the extraordinary heating-power of steam. On devising some experiments he came to the surprising conclusion that water converted into steam can heat six times its own weight of cold water up to the boilingpoint. Thinking that he must have blundered somewhere, he consulted Black. He then learned that he had stumbled on the fact, the discovery and explanation of which had made Black famous, namely, the phenomenon of Latent! Heat. When water is boiling, however much you go on heating it, it will get no hotter. The steam receives the heat without raising its own temperature and holds it in store. This heat is described as " latent." If the steam is driven through a volume of cold water it naturally condenses, and in so doing it releases its store of latent heat, which all goes to raise the temperature of the water. In other words, the heating power of a certain quantity of water at a temperature of 2I2 is trifling compared with the heating power of the same quantity of water converted into steam also at a sensible temperature of 2I2.
In order to appreciate the way in which Watt applied these scientific observations to the problem of perfecting the steam-engine, it is essential to understand exactly how the Newcomen engine of the day worked. With the aid of a diagram that should not be difficult. The figure on page 7 I represents an engine of this type reduced to the simplest terms. A is a furnace, and B is a boiler in which steam is generated. The boiler communicates by a pipe in which is a cock, a, with the cylinder, C, in which works a piston, D. It will be noticed that the cylinder is open at the top. The rod of the piston is attached to a beam, EE, pivoted at the centre, to the other end of which is fastened the rod of a pump, G. and on this rod is a weight, F. H is a cistern of cold water with a pipe running down into the bottom of the cylinder in such a way that, whenever the cock, h, is opened, a jet of water IS injected into the cylinder. Imagine the beam EE horizontal. The cock b is opened, letting steam into the cylinder. This balances the pressure of the atmosphere on the piston, and the weight F. finding no resistance at the other end of the beam, sinks down to the position shown in the diagram, drawing the piston to the top of the cylinder. The cylinder is now full of steam. When the cock b is shut, the cock h is opened, letting a jet of cold water enter the cylinder, which at once condenses the steam and creates a vacuum. The piston then makes its stroke, driven by atmospheric pressure, and so raises the pump rod. But there is now some water in the cylinder, partly condensed steam, partly the water that formed the jet. When, therefore, cock b is opened again, cock c is also opened, and this water is drained away down the pipe that enters the bottom of the cylinder on the left in the diagram. In this way the pump is kept working .the stroke of the piston sucking the water up into it, and the fall of the weight driving it out again.
Watt, equipped with new knowledge, turned again to his model. He could now calculate what volume of steam was being generated for each stroke of the piston. He compared this with the volume needed to fill the cylinder, and found that it was three or four times as great. In fact, as much as three-quarters of the steam was being wasted. His precise, orderly mind was shocked by this discovery. And the defect was not due to some detail in the machine; it was fundamental. To condense the steam and create a vacuum, the cylinder had to be cooled. When fresh steam was admitted for the next stroke it went on condensing, uselessly, until it had heated the cylinder up to its own temperature. There lay the waste. It had been worse still in the first Newcomen engines, where the cylinder was cooled by being douched with cold water outside. The internal jet condensed the steam without making the walls of the cylinder so cold. That was why it had been adopted. But the waste of steam, though reduced, was still enormous. The obvious lesson to be learned from this was that the jet must be as small as possible in order to cool the cylinder as little as possible. His observations on Latent Heat taught that when the steam in the cylinder was being condensed it gave out its immense store of heat, which went to raise the temperature of the water that had been injected. There was a danger that, instead of the cold water condensing the steam, the steam would vaporise the water. If this happened at all, the vacuum would be incomplete, and there would be some steam left in the cylinder to resist the descent of the piston. His first series of experiments had shown him that, as the water was in a vacuum, it did not need to be heated to boiling point, namely 212~~ before it turned to vapour; it would boil at the much lower temperature of I00. The conclusion was that the machine was, in fact, always being clogged by vapour under the piston, and the only way to reduce this defect was to inject a lot of cold water, too much for the steam to heat to I00; the jet must be as large as possible.
He seemed to be stuck. If the oracle of science, when consulted by its most accomplished high priest, replies that the jet must be as small as possible, but, on the other hand, it must be as large as possible, the inquirer can only curse the oracle and make a jet of medium size. This was precisely what the engineers had done. But Watt was not satisfied. An engine that was so wasteful offended his sense of mechanical beauty. He refused to confess himself beaten. " Nature," he used to say, " has a weak side, if we can only find it out." He put his case to himself in a new way. The cylinder must never be at a temperature of less than 2I2 otherwise steam will be prematurely condensed and wasted. The cylinder must always be at a temperature of less than I00otherwise the water that is injected will turn to vapour and obstruct the action of the Pi machine. Was that any more helpful ? It hardly seemed so. For days he walked about torturing his brain in the effort to achieve the impossible. Then quite suddenly the simple and obvious solution dawned on him. It all happened on a Sunday afternoon walk. There must be two different temperatures. Very well; then there must be two separate vessels. Keep the cylinder always hot, and condense the steam somewhere else. Make a separate condenser, communicating with the cylinder, and keep that always cold. Not a particle of heat will be wasted. Start with both the cylinder and the condenser full of steam. Condense the steam in the condenser and make a vacuum there. In will rush the steam from the cylinderfor steam is elasticmaking a vacuum there, at second hand, as it were. Down will come the piston. The thing is done. " I had not walked farther than the Golf House when the whole thing was arranged in my mind."
When the substance of Watt's great invention is put down in black and white it hardly seems to provide a sufficient excuse for writing a biography of the inventor. It merely carried the improvements of Savery and Newcomen one step farther. Papin had one vessel only, which served as boiler, cylinder and condenser. Newcomen, in order to reduce the waste of heat, adopted Savery's idea and had two separate vessels, a boiler and a cylinder- condenser. Watt, in order to reduce the waste still further, had three.
But technically Watt's claim to the title of inventor of the steam- engine is indisputable. Newcomen's machine made use of steam, but it was driven by the force of the atmosphere, and was often, with ~ greater accuracy, called an " atmospheric engine." The nature of Watt's improvement led him to cut out the air altogether. He wanted to keep the cylinder hot, and contact with the air was bound to cool it. There must, however, be some kind of " atmosphere " to press on the piston and drive it into the vacuum. Watt set the cylinder, just as it was, in an air-tight case filled with steam. As steam is elastic and expansive, it pressed on the piston in exactly the same way as the atmosphere in Newcomen's engine. Here, then, was an engine driven by the pressure of steam alone, the first real " steamengine." But it did not require that dangerous and expensive article, highpressure steam. It was satisfied with the safe, familiar, low-pressure steam, assisted in its action by a vacuum that eliminated resistance.
Watt's invention led directly to a further improvement of equal importance. Up till now engines had only one driving stroke, the downward one. The piston was drawn up by a weight on the far end of the beam. This was still the case in Watt's first engines. It could not be otherwise, since he used an open cylinder sitting in an atmosphere of steam. Very soon, however, he abandoned this in favour of a closed cylinder communicating at both ends with the boiler.l Now, when the piston was at the bottom, the steam above it was in an enclosed space in which a vacuum could be created by condensation, exactly as for the downward stroke. This would give the engine two driving strokes instead of one.
Naturally this point did not escape Watt, but he did not introduce it into his patented designs till I782. The reason was this. The " doubleacting " engine required a very complicated mechanism to connect the cylinder twice over both with the boiler and with the condenser, and to provide for the automatic opening and shutting of the various taps at the right moment. The single engine already overtaxed the intelligence of the average engineer; Watt trembled to think what might happen if he introduced him to the double. He was only waiting till the simpler machine had proved its worth and been accepted by the industrial world; then he offered them the creations of his riper genius.
But Watt's claim is not a technical one only. Newcomen's engine was a rarity, and was bound to remain a rarity, because it was uneconomical; there were few industries in which it could pay its way. Watt's engine, owing to its superiority in efficiency and economy, was able to spread from the mines to the iron foundries, from the iron foundries to the corn mills, from the corn mills to the cotton factories, until the industry of the nation had been transformed. Nor was his success due simply to the fact that his invention came at the crucial moment, and put the finishing touch to work done by others, for which others deserve the credit. Watt's contributions demanded higher qualities than were possessed by any of his predecessors. Papin was a clever scientist; Newcomenwas an ingenious mechanic. But Watt was a greater scientist than Papin and a greater mechanic than Newcomen. His invention was not just a happy inspiration. It was the fruit of months of hard work which no one without his genius could have accomplished. The solution seems simple, because he had thoroughly analysed every factor in the problem and reduced it to its simplest form. That was the most diflicult part of his task, demanding the brain of a scientist guided by the instincts of a mechanic. Newcomen had never realised what the problem was; Papin could never have solved it in practice. Watt saw it, explored it, and pressed on to its solution by a process of irresistible logic.
But that was not the end. There followed years of hard work, demanding the supreme skill of the mechanic guided by the brain of the scientist. The invention was made in I765 and patented in I769 but it was ten years before he had produced an engine that satisfied him.
All that time he was toiling away at the mechanical details, trying various forms of condenser, experimenting in devices for keeping the piston tight in the cylinder, and going over all the valves, cocks and connecting mechanism to make sure that everywhere there was perfect accuracy and perfect economy. When he had finished, the engine was, so far as the craftsmanship of the day allowed, a work of art. It was as different from its predecessors as the modern bicycle is from the velocipede of the 'eighties. In creating the steam-engine Watt created the science of mechanical engineering.