In a small pamphlet printed at Ca.s.sel in 1707,[29] Papin describes a new form of engine, in which he discards the original plan of a modified Huyghens engine, with tight-fitting piston and cylinder, raising its load by indirect action, and makes a modified Savery engine, which he calls the "Elector"s Engine," in honor of his patron.
This is the engine shown in the engraving, and as proposed to be used by him in turning a water-wheel.
[29] "Nouvelle maniere d"elever l"Eau par la Force du Feu, mis en Lumiere," par D. Papin. Ca.s.sel, 1707.
The sketch is that given by the inventor in his memoir. It consists (Fig. 18) of a steam-boiler, _a_, from which steam is led through the c.o.c.k, _c_, to the working cylinder, _n n_. The water beneath the floating-piston, _h_, which latter serves simply as a cushion to protect the steam from sudden condensation or contact with the water, is forced into the vessel _r r_, which is a large air-chamber, and which serves to render the outflow of water comparatively uniform, and the discharge occurs by means of the pipe _q_, from which the water rises to the desired height. A fresh supply of water is introduced through the funnel _k_, after condensation of the steam in _n n_, and the operation of expulsion is repeated.
[Ill.u.s.tration: FIG. 18.--Papin"s Engine and Water-Wheel, A. D. 1707.]
This machine is evidently a retrogression, and Papin, after having earned the honor of having invented the first steam-engine of the typical form which has since become so universally applied, forfeited that credit by his evident ignorance of its superiority over existing devices, and by attempting unsuccessfully to perfect the inferior device of another inventor.
Subsequently, Papin made an attempt to apply the steam-engine to the propulsion of vessels, the account of which will be given in the chapter on Steam-Navigation.
Again disappointed, Papin once more visited England, to renew his acquaintance with the _savans_ of the Royal Society; but Boyle had died during the period which Papin had spent in Germany, and the unhappy and disheartened inventor and philosopher died in 1810, without having seen any one of his many devices and ingenious inventions a practical success.
[Ill.u.s.tration]
CHAPTER II.
_THE STEAM-ENGINE AS A TRAIN OF MECHANISM._
"The introduction of new Inventions seemeth to be the very chief of all human Actions. The Benefits of new Inventions may extend to all Mankind universally; but the Good of political Achievements can respect but some particular Cantons of Men; these latter do not endure above a few Ages, the former forever. Inventions make all Men happy, without either Injury or Damage to any one single Person.
Furthermore, new Inventions are, as it were, new Erections and Imitations of G.o.d"s own Works."--BACON.
THE MODERN TYPE, AS DEVELOPED BY NEWCOMEN, BEIGHTON, AND SMEATON.
At the beginning of the eighteenth century every element of the modern type of steam-engine had been separately invented and practically applied. The character of atmospheric pressure, and of the pressure of gases, had become understood. The nature of a vacuum was known, and the method of obtaining it by the displacement of the air by steam, and by the condensation of the vapor, was understood. The importance of utilizing the power of steam, and the application of condensation in the removal of atmospheric pressure, was not only recognized, but had been actually and successfully attempted by Morland, Papin, and Savery.
Mechanicians had succeeded in making steam-boilers capable of sustaining any desired or any useful pressure, and Papin had shown how to make them comparatively safe by the attachment of the safety-valve. They had made steam-cylinders fitted with pistons, and had used such a combination in the development of power.
It now only remained for the engineer to combine known forms of mechanism in a practical machine which should be capable of economically and conveniently utilizing the power of steam through the application of now well-understood principles, and by the intelligent combination of physical phenomena already familiar to scientific investigators.
Every essential fact and every vital principle had been learned, and every one of the needed mechanical combinations had been successfully effected. It was only requisite that an inventor should appear, capable of perceiving that these known facts and combinations of mechanism, properly ill.u.s.trated in a working machine, would present to the world its greatest physical blessing.
The defects of the simple engines constructed up to this time have been noted as each has been described. None of them could be depended upon for safe, economical, and continuous work. Savery"s was the most successful of all. But the engine of Savery, even with the improvements of Desaguliers, was unsafe where most needed, because of the high pressures necessarily carried in its boilers when pumping from considerable depths; it was uneconomical, in consequence of the great loss of heat in its forcing-cylinders when the hot steam was surrounded at its entrance by colder bodies; it was slow in operation, of great first cost, and expensive in first cost and in repairs, as well as in its operation. It could not be relied upon to do its work uninterruptedly, and was thus in many respects a very unsatisfactory machine.
The man who finally effected a combination of the elements of the modern steam-engine, and produced a machine which is unmistakably a true engine--i. e., a train of mechanism consisting of several elementary pieces combined in a train capable of transmitting a force applied at one end and of communicating it to the resistance to be overcome at the other end--was THOMAS NEWCOMEN, an "iron-monger" and blacksmith of Dartmouth, England. The engine invented by him, and known as the "Atmospheric Steam-Engine," is the first of an entirely new type.
The old type of engine--the steam-engine as a simple machine--had been given as great a degree of perfection, by the successive improvements of Worcester, Savery, and Desaguliers, as it was probably capable of attaining by any modification of its details. The next step was necessarily a complete change of type; and to effect such a change, it was only necessary to combine devices already known and successfully tried.
But little is known of the personal history of Newcomen. His position in life was humble, and the inventor was not then looked upon as an individual of even possible importance in the community. He was considered as one of an eccentric cla.s.s of schemers, and of an order which, concerning itself with mechanical matters, held the lowest position in the cla.s.s.
It is supposed that Savery"s engine was perfectly well known to Newcomen, and that the latter may have visited Savery at his home in Modbury, which was but fifteen miles from the residence of Newcomen.
It is thought, by some biographers of these inventors, that Newcomen was employed by Savery in making the more intricate forgings of his engine. Harris, in his "Lexicon Technic.u.m," states that drawings of the engine of Savery came into the hands of Newcomen, who made a model of the machine, set it up in his garden, and then attempted its improvement; but Switzer says that Newcomen "was as early in his invention as Mr. Savery was in his."
Newcomen was a.s.sisted in his experiments by John Calley, who, with him, took out the patent. It has been stated that a visit to Cornwall, where they witnessed the working of a Savery engine, first turned their attention to the subject; but a friend of Savery has stated that Newcomen was as early with his general plans as Savery.
After some discussion with Calley, Newcomen entered into correspondence with Dr. Hooke, proposing a steam-engine to consist of a _steam-cylinder containing a piston similar to that of Papin"s, and to drive a separate pump_, similar to those generally in use where water was raised by horse or wind power. Dr. Hooke advised and argued strongly against their plan, but, fortunately, the obstinate belief of the unlearned mechanics was not overpowered by the disquisitions of their distinguished correspondent, and Newcomen and Calley attempted an engine on their peculiar plan. This succeeded so well as to induce them to continue their labors, and, in 1705, to patent,[30] in combination with Savery--who held the exclusive right to practise surface-condensation, and who induced them to allow him an interest with them--an engine combining a steam-cylinder and piston, surface-condensation, a separate boiler, and separate pumps.
[30] It has been denied that a patent was issued, but there is no doubt that Savery claimed and received an interest in the new engine.
In the atmospheric-engine, as first designed, the slow process of condensation by the application of the condensing water to the exterior of the cylinder, to produce the vacuum, caused the strokes of the engine to take place at very long intervals. An improvement was, however, soon effected, which immensely increased the rapidity of condensation. A jet of water was thrown directly _into_ the cylinder, thus effecting for the Newcomen engine just what Desaguliers had done for the Savery engine previously. As thus improved, the Newcomen engine is shown in Fig. 19.
Here _b_ is the boiler. Steam pa.s.ses from it through the c.o.c.k, _d_, and up into the cylinder, _a_, equilibrating the pressure of the atmosphere, and allowing the heavy pump-rod, _k_, to fall, and, by the greater weight acting through the beam, _i i_, to raise the piston, _s_, to the position shown. The rod _m_ carries a counterbalance, if needed. The c.o.c.k _d_ being shut, _f_ is then opened, and a jet of water from the reservoir, _g_, enters the cylinder, producing a vacuum by the condensation of the steam. The pressure of the air above the piston now forces it down, again raising the pump-rods, and thus the engine works on indefinitely.
[Ill.u.s.tration: FIG. 19.--Newcomen"s Engine, A. D. 1705.]
The pipe _h_ is used for the purpose of keeping the upper side of the piston covered with water, to prevent air-leaks--a device of Newcomen.
Two gauge-c.o.c.ks, _c c_, and a safety-valve, _N_, are represented in the figure, but it will be noticed that the latter is quite different from the now usual form. Here, the pressure used was hardly greater than that of the atmosphere, and the weight of the valve itself was ordinarily sufficient to keep it down. The condensing water, together with the water of condensation, flows off through the open pipe _p_.
Newcomen"s first engine made 6 or 8 strokes a minute; the later and improved engines made 10 or 12.
The steam-engine has now a.s.sumed a form that somewhat resembles the modern machine.
The Newcomen engine is seen at a glance to have been a combination of earlier ideas. It was the engine of Huyghens, with its cylinder and piston as improved by Papin, by the subst.i.tution of steam for the gases generated by the explosion of gunpowder; still further improved by Newcomen and Calley by the addition of the method of condensation used in the Savery engine. It was further modified, with the object of applying it directly to the working of the pumps of the mines by the introduction of the overhead beam, from which the piston was suspended at one end and the pump-rod at the other.
The advantages secured by this combination of inventions were many and manifest. The piston not only gave economy by interposing itself between the impelling and the resisting fluid, but, by affording opportunity to make the area of piston as large as desired, it enabled Newcomen to use any convenient pressure and any desired proportions for any proposed lift. The removal of the water to be lifted from the steam-engine proper and handling it with pumps, was an evident cause of very great economy of steam.
The disposal of the water to be raised in this way also permitted the operations of condensation of steam, and the renewal of pressure on the piston, to be made to succeed each other with rapidity, and enabled the inventor to choose, unhampered, the device for securing promptly the action of condensation.
Desaguliers, in his account of the introduction of the engine of Newcomen, says that, with his coadjutor Calley, he "made several experiments in private about the year 1710, and in the latter end of the year 1711 made proposals to drain the water of a colliery at Griff, in Warwickshire, where the proprietors employed 500 horses, at an expense of 900 a year; but, their invention not meeting with the reception they expected, in March following, through the acquaintance of Mr. Potter, of Bromsgrove, in Worcestershire, they bargained to draw water for Mr. Back, of Wolverhampton, where, after a great many laborious attempts, they did make the engine work; but, not being either philosophers to understand the reason, or mathematicians enough to calculate the powers and proportions of the parts, they very luckily, by accident, found what they sought for.
"They were at a loss about the pumps, but, being so near Birmingham, and having the a.s.sistance of so many admirable and ingenious workmen, they came, about 1712, to the method of making the pump-valves, clacks, and buckets, whereas they had but an imperfect notion of them before. One thing is very remarkable: as they were at first working, they were surprised to see the engine go several strokes, and very quick together, when, after a search, they found a hole in the piston, which let the cold water in to condense the steam in the inside of the cylinder, whereas, before, they had always done it on the outside.
They used before to work with a buoy to the cylinder, inclosed in a pipe, which buoy rose when the steam was strong and opened the injection, and made a stroke; thereby they were only capable of giving 6, 8, or 10 strokes in a minute, till a boy, named Humphrey Potter, in 1713, who attended the engine, added (what he called a _scoggan_) a catch, that the beam always opened, and then it would go 15 or 16 strokes a minute. But, this being perplexed with catches and strings, Mr. Henry Beighton, in an engine he had built at Newcastle-upon-Tyne in 1718, took them all away but the beam itself, and supplied them in a much better manner."
In ill.u.s.tration of the application of the Newcomen engine to the drainage of mines, Farey describes a small machine, of which the pump is 8 inches in diameter, and the lift 162 feet. The column of water to be raised weighed 3,535 pounds. The steam-piston was made 2 feet in diameter, giving an area of 452 square inches. The net working-pressure was a.s.sumed at 10-3/4 pounds per square inch; the temperature of the water of condensation and of uncondensed vapor after the entrance of the injection-water being usually about 150 Fahr. This gave an excess of pressure on the steam-side of 1,324 pounds, the total pressure on the piston being 4,859 pounds. One-half of this excess is counterweighted by the pump-rods, and by weight on that end of the beam; and the weight, 662 pounds, acting on each side alternately as a surplus, produced the requisite rapidity of movement of the machine. This engine was said to make 15 strokes per minute, giving a speed of piston of 75 feet per minute, and the power exerted usefully was equivalent to 265,125 pounds raised one foot high per minute. As the horse-power is equivalent to 33,000 "foot-pounds" per minute, the engine was of 265125/33000 = 8.034--almost exactly 8 horse-power.
It is instructive to contrast this estimate with that made for a Savery engine doing the same work. The latter would have raised the water about 26 feet in its "suction-pipe," and would then have forced it, by the direct pressure of steam, the remaining distance of 136 feet; and the steam-pressure required would have been nearly 60 pounds per square inch. With this high temperature and pressure, the waste of steam by condensation in the forcing-vessels would have been so great that it would have compelled the adoption of two engines of considerable size, each lifting the water one-half the height, and using steam of about 25 pounds pressure. Potter"s rude valve-gear was soon improved by Henry Beighton, in an engine which that talented engineer erected at Newcastle-upon-Tyne in 1718, and in which he subst.i.tuted substantial materials for the cords, as in Fig. 20.
In this sketch, _r_ is a plug-tree, plug-rod, or plug-frame, as it is variously called, suspended from the great beam, with which it rises and falls, bringing the pins _p_ and _k_, at the proper moment, in contact with the handles _k k_ and _n n_ of the valves, moving them in the proper direction and to the proper extent. A lever safety-valve is here used, at the suggestion, it is said, of Desaguliers. The piston was packed with leather or with rope, and lubricated with tallow.
[Ill.u.s.tration: FIG. 20.--Beighton"s Valve-Gear, A. D. 1718.]
After the death of Beighton, the atmospheric engine of Newcomen retained its then standard form for many years, and came into extensive use in all the mining districts, particularly in Cornwall, and was also applied occasionally to the drainage of wet lands, to the supply of water to towns, and it was even proposed by Hulls to be used for ship-propulsion.
The proportions of the engines had been determined in a hap-hazard way, and they were in many cases very unsafe. John Smeaton, the most distinguished engineer of his time, finally, in 1769, experimentally determined proper proportions, and built several of these engines of very considerable size. He built his engines with steam-cylinders of greater length of stroke than had been customary, and gave them such dimensions as, by giving a greater excess of pressure on the steam-side, enabled him to obtain a greatly-increased speed of piston.
The first of his new style of engine was erected at Long Benton, near Newcastle-upon-Tyne, in 1774.
Fig. 21[31] ill.u.s.trates its princ.i.p.al characteristic features. The boiler is not shown.
[31] A fac-simile of a sketch in Galloway"s "On the Steam-Engine,"
etc.
The steam is led to the engine through the pipe, _C_, and is regulated by turning the c.o.c.k in the receiver, _D_, which connects with the steam-cylinder by the pipe, _E_, which latter pipe rises a little way above the bottom of the cylinder, _F_, in order that it may not drain off the injection-water into the steam-pipe and receiver.
The steam-cylinder, about ten feet in length, is fitted with a carefully-made piston, _G_, having a flanch rising four or five inches and extending completely around its circ.u.mference, and nearly in contact with the interior surface of the cylinder. Between this flanch and the cylinder is driven a "packing" of oak.u.m, which is held in place by weights; this prevents the leakage of air, water, or steam, past the piston, as it rises and falls in the cylinder at each stroke of the engine. The chain and piston-rod connect the piston to the beam, _I I_. The arch-heads at each end of the beam keep the chains of the piston-rod and the pump-rods perpendicular and in line.