Читать книгу The Gallery of Portraits (All 7 Volumes) - Arthur Thomas Malkin - Страница 25

Table of Contents

Those who by cultivating the arts of peace have risen from obscurity to fame and wealth, seldom leave to the biographer such ample memorials of their private lives as he could wish to work upon. The details of a life spent in the laboratory or in the workshop rarely present much variety; or possess much interest, except when treated scientifically for the benefit of the scientific reader. Such is the case with James Watt: the history of his long and prosperous life is little more than the history of his scientific pursuits; and this must plead our excuse if it chance that the reader should here find less personal information about him than he may desire. Fortunately his character has been sketched before it was too late, by the masterly hand of one who knew him well. Most of the accounts of him already published are said, by those best qualified to judge, to be inaccurate. The same authority is pledged to the general correctness of the article Watt, in the supplement to the Encyclopædia Britannica, and from that article the facts of this short memoir are taken.

Both the grandfather and uncle of James Watt were men of some repute in the West of Scotland, as mathematical teachers and surveyors. His father was a merchant at Greenock, where Watt was born, June 19, 1736, and where he received the rudiments of his education. Our knowledge of the first twenty years of his life may be comprised in a few short sentences. At an early age he manifested a partiality for the practical part of mechanics, which he retained through life, taking pleasure in the manual exercise of his early trade, even when hundreds of hands were ready to do his bidding. In his eighteenth year he went to London, to obtain instruction in the profession of a mathematical instrument-maker; but he remained there little more than a year, being compelled to return home by the precariousness of his health.

In 1757, shortly after his return home, he was appointed instrument-maker to the University of Glasgow, and accommodated with premises within the precincts of that learned body. Robert Simpson, Adam Smith, and Dr. Black, were then some of the professors; and from communication with such men, Watt could not fail to derive the most valuable mental discipline. With Dr. Black, and with John Robison, then a student, afterwards eminent as a mathematician and natural philosopher, he formed a friendship which was continued through life. In 1763 he removed into the town of Glasgow, intending to practise as a civil engineer, and in the following year was married to his cousin Miss Miller.

In the winter of 1763–4, his mind was directed to the earnest prosecution of those inventions which have made his name celebrated over the world, by having to repair a working model of a steam-engine on Newcomen’s construction, for the lectures of the Professor of Natural Philosophy. In treating this subject, we must presume that the reader possesses a competent acquaintance with the history and construction of the steam-engine. Those who do not possess the requisite knowledge, will find it briefly and clearly stated in a short treatise written by Mr. Farey, and in many works of easy access. Newcomen’s engine, at the time of which we speak, was of the last and most approved construction. The moving power was the weight of the air pressing on the upper side of a piston working in a cylinder; steam being employed at the termination of each downward stroke to raise the piston with its load of air up again, and then to form a vacuum by its condensation when cooled by a jet of cold water, which was thrown into the cylinder when the admission of steam was stopped. Upon repairing the model, Watt was struck by the incapability of the boiler to produce a sufficient supply of steam, though it was larger in proportion to the cylinder than was usual in working engines. This arose from the nature of the cylinder, which being made of brass, a better conductor of heat than cast-iron, and presenting, in consequence of its small size, a much larger surface in proportion to its solid content than the cylinders of working engines, necessarily cooled faster between the strokes, and therefore at every fresh admission consumed a greater proportionate quantity of steam. But being made aware of a much greater consumption of steam than he had imagined, he was not satisfied without a thorough inquiry into the cause. With this view he made experiments upon the merits of boilers of different constructions; on the effect of substituting a less perfect conductor, as wood, for the material of the cylinder; on the quantity of coal required to evaporate a given quantity of water; on the degree of expansion of water in the shape of steam: and he constructed a boiler which showed the quantity of water evaporated in a given time, and thus enabled him to calculate the quantity of steam consumed at each stroke of the engine. This proved to be several times the content of the cylinder. He soon discovered that, whatever the size and construction of the cylinder, an admission of hot steam into it must necessarily be attended with very great waste, if, in condensing the steam previously admitted, that vessel had been cooled down sufficiently to produce a vacuum at all approaching to a perfect one. If, on the other hand, to prevent this waste, he cooled it less thoroughly, a considerable quantity of steam remained uncondensed within, and by its resistance weakened the power of the descending stroke. These considerations pointed out a vital defect in Newcomen’s construction: involving either a loss of steam, and consequent waste of fuel, or a loss of power from the piston’s descending at every stroke through a very imperfect vacuum.

It soon occurred to Watt, that if the condensation were performed in a separate vessel, one great evil, the cooling of the cylinder, and the consequent waste of steam, would be avoided. The idea once started, he soon verified it by experiment. By means of an arrangement of cocks, a communication was opened between the cylinder, and a distinct vessel exhausted of its air, at the moment when the former was filled with steam. The vapour of course rushed to fill up the vacuum, and was there condensed by the application of external cold, or by a jet of water: so that fresh steam being continually drawn off from the cylinder to supply the vacuum continually created, the density of that which remained might be reduced within any assignable limits. This was the great and fundamental improvement.

Still, however, there was a radical defect in the atmospheric engine, inasmuch as the air being admitted into the cylinder at every stroke, a great deal of heat was abstracted, and a proportionate quantity of steam wasted. To remedy this, Watt excluded the air from the cylinder altogether; and recurred to the original plan of making steam the moving power of the engine, not a mere agent to produce a vacuum. In removing the difficulties of construction which beset this new plan, he displayed great ingenuity and powers of resource. On the old plan, if the cylinder was not bored quite true, or the piston not accurately fitted, a little water poured upon the top rendered it perfectly air-tight, and the leakage into the cylinder was of little consequence, so long as the injection water was thrown into that vessel. But on the new plan, no water could possibly be admitted within the cylinder; and it was necessary, not merely that the piston should be air-tight, but that it should work through an air-tight collar, that no portion of the steam admitted above it might escape. This he accomplished by packing the piston and the stuffing-box, as it is called, through which the piston-rod works, with hemp. A farther improvement consisted in equalizing the motion of the engine by admitting the steam alternately above and below the piston, by which the power is doubled in the same space, and with the same strength of material. The vacuum of the condenser was perfected by adding a powerful pump, which at once drew off the condensed, and injection water, and with it any portion of air which might find admission; as this would interfere with the action of the engine, if allowed to accumulate. His last great change was to cut off the communication between the cylinder and the boiler, when a portion only, as one-third or one-half, of the stroke was performed; leaving it to the expansive power of the steam to complete it. By this, economy of steam was obtained; together with the power of varying the effort of the engine according to the work which it has to do, by admitting the steam through a greater or smaller portion of the stroke.

These are the chief improvements which Watt effected at different periods of his life. Of the patient ingenuity by which they were rendered complete, and the many beautiful contrivances by which he gave to senseless matter an almost instinctive power of self-adjustment, with precision of action more than belongs to any animated being, we cannot speak; nor would it be easy to render description intelligible without the help of diagrams. His first patent bears date June 5, 1769, so that some time elapsed between the invention and publication of his improvements. The delay arose partly from his own want of funds, and the difficulty of finding a person possessed of capital, who could appreciate the merit of his invention; partly from his own increasing occupation as a civil engineer. In that capacity he soon acquired reputation, and was employed in various works of importance. In 1767 he made a survey for a canal, projected, but not executed, between the Clyde and Forth. He also made the original survey for the Crinan Canal, since carried into effect by Mr. Rennie; and was employed extensively in forming harbours, deepening rivers, constructing bridges, and all the most important labours of his profession. The last and greatest work of this kind on which he was employed, was a survey for a canal between Fort William and Inverness, where the Caledonian Canal now runs.

At last Dr. Roebuck, the establisher of the Carron iron-works, became Watt’s partner in the patent, upon condition that he should supply the necessary funds for bringing out the invention, and receive in return two-thirds of the profit. That gentleman, however, was unable to fulfil his share of the contract, and in 1774 resigned his interest to Mr. Boulton, the proprietor of the Soho works, near Birmingham. Watt then determined to remove his residence to England; a step to which he probably was rendered more favourable by the death of his wife in 1773. In 1775, Parliament, in consideration of the national importance of Mr. Watt’s inventions, and the difficulty and expense of introducing them to public notice, prolonged the duration of his patent for twenty-five years.

The partners now erected engines for pumping water upon a large scale, and it was found by comparative trials that the saving of fuel amounted to three-fourths of the whole quantity consumed by the engines formerly in use. This fact once established, the new machine was soon introduced into the deep mines of Cornwall, where, of all places, its merits could best be tried. The patentees were paid by receiving one-third of the savings of fuel. From the time that the new value of their invention was fully proved, Messrs. Boulton and Watt had to maintain a harassing contest with numerous invaders of their patent rights; and it was not until near the expiration of the patent in 1800, that the question was definitively settled in their favour. These attacks, however, did not prevent Watt from realizing an ample fortune, the well-earned reward of his industry and ability, with which he established himself at Heathfield, in the county of Stafford.

At one period Watt devoted much attention to the construction of a rotary engine, in which the power of the steam should be applied directly to produce circular motion. Like all who have yet attempted to solve this problem, he failed to obtain a satisfactory result; and turned his attention in consequence to discover the best means of converting reciprocal into rotary motion. For this purpose he originally intended to use the crank; but having been forestalled by a neighbouring manufacturer, who took out a patent for it, having obtained his knowledge, as it is said, surreptitiously from one of Watt’s workmen, he invented the combination called the sun and planet wheels. Afterwards he recurred to the crank, without a shadow of opposition from the patentee. He was also the author of that elegant contrivance, the parallel motion, which superseded the old-fashioned beam and chain, and rendered possible the introduction of the double engine, in which an upward, as well as a downward force is applied.

His attention, however, was not confined to the subject of steam. He invented a copying machine, for which he took out a patent, in 1780. In the winter of 1784–5, he erected an apparatus, the first of its kind, for warming his apartments by steam. He also introduced into England the method of bleaching with oxymuriatic acid, or chlorine, invented and communicated to him for publication by his friend Berthollet. Towards the conclusion of life, he constructed a machine for making fac-similes of busts and other carved work; and also busied himself in forming a composition for casts, possessing much of the transparency and hardness of marble.

With chemistry Watt was well acquainted. In 1782 he published a paper in the Philosophical Transactions, entitled, ‘Thoughts on the constituent parts of Water, and of Dephlogisticated Air.’ His only other literary undertaking was the revision of Professor Robison’s articles on Steam and Steam Engines, in the Encyclopædia Britannica, to which he added notes containing an account of his own experiments on steam, and a history of his improvements in the engine.

About the year 1775 he married his second wife, Miss Macgregor. Though his health had been delicate through life, yet he reached the advanced age of eighty-four. He died at his house at Heathfield, August 25, 1819. Chantrey made a bust of him some years before his death; from which the same distinguished artist has since executed two marble statues, one for his tomb, the other for the Hunterian Museum at Glasgow; and a third in bronze, also for Glasgow, which has recently been erected there. It represents Watt seated in deep thought, a pair of compasses in his hand, and a scroll, on which is the draught of a steam-engine, open on his knee.

We cannot better close this account, than with a short extract from the sketch of his character, to which we have alluded in a former page. After speaking of the lasting celebrity which Watt has acquired by his mechanical inventions, the author continues, that “to those to whom he more immediately belonged, who lived in his society and enjoyed his conversation, this is not, perhaps, the character in which he will be most frequently recalled—most deeply lamented—or even most highly admired. Independently of his great attainments in mechanics, Mr. Watt was an extraordinary and in many respects a wonderful man. Perhaps no individual in his age possessed so much and such varied and exact information, had read so much, or remembered what he had read so accurately and well. He had infinite quickness of apprehension, a prodigious memory, and a certain rectifying and methodising power of understanding, which extracted something precious out of all that was presented to it. His stores of miscellaneous knowledge were immense, and yet less astonishing than the command he had at all times over them. It seemed as if every subject that was casually started in conversation with him, had been that which he had been last occupied in studying and exhausting; such was the copiousness, the precision, and the admirable clearness of the information which he poured out upon it without effort or hesitation. Nor was this promptitude and compass of knowledge confined, in any degree, to the studies connected with his ordinary pursuits. That he should have been minutely and extensively skilled in chemistry and the arts, and in most of the branches of physical science, might, perhaps, have been conjectured; but it could not have been inferred from his usual occupations, and probably is not generally known, that he was curiously learned in many branches of antiquity, metaphysics, medicine, and etymology; and perfectly at home in all the details of architecture, music, and law. He was well acquainted, too, with most of the modern languages, and familiar with their most recent literature. Nor was it at all extraordinary to hear the great mechanician and engineer detailing and expounding, for hours together, the metaphysical theories of the German logicians, or criticising the measures or the matter of the German poetry. * * *

“It is needless to say, that with those vast resources, his conversation was at all times rich and instructive in no ordinary degree. But it was, if possible, still more pleasing than wise, and had all the charms of familiarity, with all the substantial treasures of knowledge. No man could be more social in his spirit, less assuming or fastidious in his manners, or more kind and indulgent towards all who approached him. * * * His talk, too, though overflowing with information, had no resemblance to lecturing, or solemn discoursing; but, on the contrary, was full of colloquial spirit and pleasantry. He had a certain quiet and grave humour, which ran through most of his conversation, and a vein of temperate jocularity, which gave infinite zest and effect to the condensed and inexhaustible information which formed its main staple and characteristic. There was a little air of affected testiness, and a tone of pretended rebuke and contradiction, which he used towards his younger friends, that was always felt by them as an endearing mark of his kindness and familiarity, and prized accordingly, far beyond all the solemn compliments that ever proceeded from the lips of authority. His voice was deep and powerful; though he commonly spoke in a low and somewhat monotonous tone, which harmonized admirably with the weight and brevity of his observations, and set off to the greatest advantage the pleasant anecdotes which he delivered with the same grave tone, and the same calm smile playing soberly on his lips. There was nothing of effort, indeed, or of impatience, any more than of pride or levity, in his demeanour; and there was a finer expression of reposing strength, and mild self-possession in his manner, than we ever recollect to have met with in any other person. He had in his character the utmost abhorrence for all sorts of forwardness, parade, and pretension; and indeed never failed to put all such impostors out of countenance, by the manly plainness and honest intrepidity of his language and deportment.

“He was twice married, but has left no issue but one son, long associated with him in his business and studies, and two grandchildren by a daughter who predeceased him. He was fellow of the Royal Societies both of London and Edinburgh, and one of the few Englishmen who were elected members of the National Institute of France. All men of learning and of science were his cordial friends; and such was the influence of his mild character, and perfect fairness and liberality, even upon the pretender to these accomplishments, that he lived to disarm even envy itself, and died, we verily believe, without a single enemy.”