Читать книгу Triumphs of Invention and Discovery in Art and Science - J. Hamilton Fyfe - Страница 13

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As the last century was drawing to its close, two great revolutions were in progress, both of which were destined to exercise a mighty influence upon the years to come,—the one calm, silent, peaceful, the other full of sound and fury, bathed in blood, and crowned with thorns,—the one the fruit of long years of patient thought and work, the other the outcome of long years of oppression, suffering, and sin,—the one was Watt's invention of the steam engine, the other the great popular revolt in France. These are the two great events which set their mark upon our century, gave form and colour to its character, and direction to its aims and aspirations. In the pages of conventional history, of course, the French revolution, with its wild phantasmagoria of retribution, its massacres and martyrdoms, will no doubt have assigned to it the foremost rank as the great feature of the era,—

"For ever since historians writ,

And ever since a bard could sing,

Doth each exalt with all his wit

The noble art of murdering."

But those who can look below the mere surface of events, and whose fancy is not captivated by the melo-drama of rebellion, and the pageantry of war, will find that Watt's steam machine worked the greatest revolution of modern times, and exercised the deepest, as well as widest and most permanent influence over the whole civilized world.

Like all great discoveries, that of the motive power of steam, and the important uses to which it might be applied, was the work, not of any one mind, but of several minds, each borrowing something from its predecessor, until at last the first vague and uncertain Idea was developed into a practical Reality. Known dimly to the ancients, and probably employed by the priests in their juggleries and pretended miracles, it was not till within the last three centuries that any systematic attempt was made to turn it to useful account.

But before we turn our attention to the persons who made, and, after many failures and discouragements, successfully made this attempt, it will be advisable we should say something as to the principle on which their invention is founded.

The reader knows that gases and vapours, when imprisoned within a narrow space, do struggle as resolutely to escape as did Sterne's starling from his cage. Their force of pressure is enormous, and if confined in a closed vessel, they would speedily rend it into fragments. Let some water boil in a pipkin whose lid fits very tightly; in a few minutes the vapour or steam arising from the boiling water, overcoming the resistance of the lid, raises it, and rushes forth into the atmosphere.

Take a small quantity of water, and pour it into the hollow of a ball of metal. Then with the aid of a cork, worked by a metallic screw, close the opening of the ball hermetically, and place the ball in the heart of a glowing fire. The steam formed by the boiling water in the inside of the metallic bomb, finding no channel of escape, will burst through the bonds that sought to confine it, and hurl afar the fragments with a loud and dangerous explosion.

These well-known facts we adduce simply as a proof of the immense mechanical power possessed by steam when enclosed within a limited area. Now, the questions must have occurred to many, though they were themselves unable to answer them,—Why should all this force be wasted? Can it not be directed to the service and uses of man? In the course of time, however, human intelligence did discover a sufficient reply, and did contrive to utilize this astonishing power by means of the machine now so famous as the Steam Engine.

Let us take a boiler full of water, and bring it up to boiling point by means of a furnace. Attach to this boiler a tube, which guides the steam of the boiler into a hollow metallic cylinder, traversed by a piston rising and sinking in its interior. It is evident that the steam rushing through the tube into the lower part of the cylinder, and underneath the piston, will force the piston, by its pressure, to rise to the top of the cylinder. Now let us check for a moment the influx of the steam below the piston, and turning the stopcock, allow the steam which fills that space to escape outside; and, at the same time, by opening a second tube, let in a supply of steam above the piston: the pressure of the steam, now exercised in a downward direction, will force the piston to the bottom of its course, because there will exist beneath it no resistance capable of opposing the pressure of the steam. If we constantly keep up this alternating motion, the piston now rising and now falling, we are in a position to profit by the force of steam. For if the lever, attached to the rod of the piston at its lower end, is fixed by its upper to a crank of the rotating axle of a workshop or factory, is it not clear that the continuous action of the steam will give this axle a continuous rotatory movement? And this movement may be transmitted, by means of bands and pulleys, to a number of different machines or engines all kept at work by the power of a solitary engine.

This, then, is the principle on which the inventions of Papin, the Marquis of Worcester, Newcomen, and James Watt have been based.

The great astronomer Huyghens conceived the idea of creating a motive machine by exploding a charge of gunpowder under a cylinder traversed by a piston: the air contained in this cylinder, dilated by the heat resulting from the combustion of the powder, escaped into the outer air through a valve, whereupon a partial void existed beneath the piston, or, rather, the air considerably rarified; and from this moment the pressure of the atmospheric air falling on the upper part of the piston, and being but imperfectly counterpoised by the rarified air beneath the piston, precipitated this piston to the bottom of the cylinder. Consequently, said Huyghens, if to the said piston were attached a chain or cord coiling around a pulley, one might raise up the weights placed at the extremity of the cord, and so produce a genuine mechanical effect.

GENERAL PRINCIPLE OF THE STEAM ENGINE.

But Experiment, the touchstone of Physical Truth, soon revealed the deficiencies of an apparatus such as Huyghens had suggested. The air beneath the piston was not sufficiently rarified; the void produced was too imperfect. Evidently gunpowder was not the right agent. What was? Denis Papin answered, Steam. And the first Steam Engine ever invented was invented by this ingenious Frenchman.

Papin was born at Blois on the 22nd of August 1645. He died about 1714, but neither the exact date nor the place of his death is known. The lives of most men of genius are heavy with shadows, but Papin's career was more than ordinarily characterized by the incessant pursuit of the evil spirits of adversity and persecution. A Protestant, and devoutly loyal to his creed, he fled from France with thousands of his co-religionists, when Louis XIV. unwisely and unrighteously revoked the Edict of Nantes, which permitted the Huguenots to worship God after their own fashion. And it was abroad, in England, Italy, and Germany, that he realized the majority of his inventions, among which that of the Steam Engine is the most conspicuous.

In 1707 Papin constructed a steam engine on the principle we have already described, and placed it on board a boat provided with wheels. Embarking at Cassel on the river Fulda, he made his way to Münden in Hanover, with the design of entering the waters of the Weser, and thence repairing to England, to make known his discovery, and test its capabilities before the public. But the harsh and ignorant boatmen of the Weser would not permit him to enter the river; and when he indignantly complained, they had the barbarity to break his boat in pieces. This was the crowning misfortune of Papin's life. Thenceforward he seems to have lost all heart and hope. He contrived to reach London, where the Royal Society, of which he was a member, allowed him a small pittance.

In 1690 this ingenious man had devised an engine in which atmospheric vapour instead of steam was the motive agent. At a later period, Newcomen, a native of Dartmouth in Devonshire, conceived the idea of employing the same source of power.

But, previously, the value of steam, if employed in this direction, had occurred to the Marquis of Worcester, a nobleman of great ability and a quick imagination, who, for his loyalty to the cause of Charles I., had been confined in the Tower of London as a prisoner. On one occasion, while sitting in his solitary chamber, the tight cover of a kettle full of boiling water was blown off before his eyes; for mere amusement's sake he set it on again, saw it again blown off, and then began to reflect on the capabilities of power thus accidentally revealed to him, and to speculate on its application to mechanical ends. Being of a quick, ingenious turn of mind, he was not long in discovering how it could be directed and controlled. When he published his project—"An Admirable and Most Forcible Way to Drive up Water by Fire"—he was abused and laughed at as being either a madman or an impostor. He persevered, however, and actually had a little engine of some two horse power at work raising water from the Thames at Vauxhall; by means of which, he writes, "a child's force bringeth up a hundred feet high an incredible quantity of water, and I may boldly call it the most stupendous work in the whole world." There is a fervent "Ejaculatory and Extemporary Thanksgiving Prayer" of his extant, composed "when first with his corporeal eyes he did see finished a perfect trial of his water-commanding engine, delightful and useful to whomsoever hath in recommendation either knowledge, profit, or pleasure." This and the rest of his wonderful "Centenary of Inventions," only emptied instead of replenishing his purse. He was reduced to borrow paltry sums from his creditors, and received neither respect for his genius nor sympathy for his misfortunes. He was before his age, and suffered accordingly.

In 1698 his work was taken up by Thomas Savery, a miner, who, through assiduous labour and well-directed study, had become a skilful engineer. He succeeded in constructing an engine on the principle of the pressure of aqueous vapour, and this engine he employed successfully in pumping water out of coal mines. We owe to Savery the invention of a vacuum, which was suggested to him, it is said, in a curious manner: he happened to throw a wine-flask, which he had just drained, upon the fire; a few drops of liquor at the bottom of the flask soon filled it with steam, and, taking it off the fire, he plunged it, mouth downwards, into a basin of cold water that was standing on the table, when, a vacuum being produced, the water immediately rushed up into the flask.

In tracing this lineage of inventive genius, we next come to Thomas Newcomen, a blacksmith, who carried out the principle of the piston in his Atmospheric Engine, for which he took out a patent in 1705. It is but just to recognize that this engine was the first which proved practically and widely useful, and was, in truth, the actual progenitor of the present steam engine. It was chiefly used for working pumps. To one end of a beam moving on a central axis was attached the rod of the pump to be worked; to the other, the rod of the piston moving in the cylinder below. Underneath this cylinder was a boiler, and the two were connected by a pipe provided with a stop-cock to regulate the supply of steam. When the pump-rod was depressed, and the piston raised to the top of the cylinder, which was effected by weights hanging to the pump-end of the beam, the stop-cock was used to cut off the steam, and a supply of cold water injected into the cylinder through a water-pipe connected with the tank or cistern. The steam in the cylinder was immediately condensed; a vacuum created below the piston; the latter was then forced down by atmospheric pressure, bringing with it the end of the beam to which it was attached, and raising the other along with the pump-rod. A fresh supply of steam was admitted below the piston, which was raised by the counterpoise; and thus the motion was constantly renewed. The opening and shutting of the stop-cocks was at first managed by an attendant; but a boy named Potter, who was employed for this purpose, being fonder of play than work, contrived to save himself all trouble in the matter by fastening the handles with pieces of string to some of the cranks and levers. Subsequently, Beighton, an engineer, improved on this idea by substituting levers, acted on by pins in a rod suspended from the beam.

Properly speaking, Newcomen's engine was not a steam, but an atmospheric engine; for though steam was employed, it formed no essential feature of the contrivance, and might have been replaced by an air-pump. All the use that was made of steam was to produce a vacuum underneath the piston, which was pressed down by the weight of the atmosphere, and raised by the counterpoise of the buckets at the other end of the beam. Watt, in bringing the expansive force of steam to bear upon the working of the piston, may be said to have really invented the steam engine. Half a century before the little model came into Watt's hands, Newcomen's engine had been made as complete as its capabilities admitted of; and Watt struck into an entirely new line, and invented an entirely new machine, when he produced his Condensing Engine.