JAMES WATT, the world's most illustrious mechanic, was born at Greenock, Scotland, on the 19th of January, 1736. His father enjoyed a good social position, and was held in high esteem by his fellow-townsmen, having been appointed one of the magistrates of the town. The subject of our memoir received the rudiments of his education in his native place, the delicacy of his health prohibiting a resort to other and more distant academies. The natural studiousness of his disposition was perhaps increased by this weakliness. Reading supplied the place of rougher and less serviceable exercises. So tenacious was his memory, that at a very early age he was well informed on many subjects of a scientific character, especially those branches which were connected more or less with mechanics. Except that he was a quiet, amiable, studious youth, we know nothing of any particular importance concerning the early years of his life. At the age of eighteen he was sent to London to be apprenticed to a maker of mathematical instruments, but, in little more than a year, the feebleness of his health compelled him to abandon this profession and return to

his home. He appears to have had a liking for the business, however, and probably practiced it until he felt that he knew enough to start for himself. This he did at Glasgow in 1757, and was appointed mathematical instrument maker to the college. He retained this situation for many years, and was able greatly to improve himself in every department of knowledge. One of his principal occupations was the repairing of the scientific apparatus of the college. The dexterity with which he did this, and the amount of knowledge he possessed on most mechanical subjects, brought him into friendly contact with the various professors. They met in his little room, and discussed subjects of natural philosophy, and no doubt theorized largely on all the leading topics of the day. One of young Watt's most frequent visitors was Mr. (afterward Dr.) Robison, who at that time was speculating on the possibility of applying steam as a motive power to wheel carriages. Watt had himself made some experiments on the elasticity of steam, assured that vast forces were yet to be secured from it. The steam-engine was then but slightly known, and, owing to its many imperfections, still more slightly used. Some recent improvements made by Newcomen only served to indicate what might be accomplished. While the two friends were discussing the matter, a model was sent in to be repaired by the professor of natural philosophy. On examination, it proved to be a miniature copy of Newcomen's improved engine. This treasure was eagerly examined by Watt, and criticised with technical exactitude. In a very little while he discovered the reason why the model would not work, and at the same time saw that, however admirably it might perform its functions, it was still an imperfect machine. With the view of remedying its defects, he commenced an extensive series of experiments. The boiler and the generation of steam were the first objects of his attention. He was soon rewarded with many valuable discoveries. The rapidity with which water evaporates, he found, depended on certain causes which were before unknown to him. He also ascertained the quantity of coals necessary for the evaporation of any given quantity of water; the heat at which water boils under various pressures, and many other particulars of a similar kind, many of which had never before been determined. When he had disposed of these questions, he turned his attention to the cylinder, which he declared to be radically defective. In Newcomen's

engine, it had to be cooled after every stroke of the piston, in order to condense the waste steam. This was effected in an ingenious way, by the injection of a small jet of cold water into the cylinder, but it occasioned a great waste of power and an extravagant expenditure of fuel. If, argued Watt, the cylinder, instead of being thus cooled for every stroke of the piston, could be kept permanently hot, a fourth part of the heat which had been hitherto applied would be found sufficient. The question now was how this desirable object could be accomplished. It was his constant theme, walking, sleeping, dreaming. All the faculties of his suggestive mind were directed to the solution of the great and important problem. After brooding over it for some time, he abandoned the idea of getting rid of the waste steam in the vessel where it had been used; he could discover no possible way of doing so in a complete and thorough manner. The next question was how to dispose of it. At last it occurred to him that it might be possible to draw it off into another vessel, and so got rid of without inconvenience. This happy idea was the first step toward the vast improvements which he afterward made. In the course of one or two days, according to his own account, he had all the apparatus arranged in his own mind. The plan was extremely simple, and on that account more practicable and valuable. He proposed to establish a communication by an open pipe between the cylinder and another vessel, the consequence of which evidently would be, that when the steam was admitted into the former, it would flow into the latter, so as to fill it also. If, then, the portion in this latter vessel only should be subjected to a condensing process by being brought into contact with cold water, or any other convenient means, what would follow? Why, a vacuum would be produced, into which more steam would immediately rush from the cylinder; that likewise would be condensed, and so the process would go on till all the steam had left the cylinder. In this way, the main cylinder would be kept nearly at an equal temperature. When these views were tested by experiment, the result was found to answer Watt's most sanguine expectations. A great saving of fuel and a vast increase of power were effected. But the genius of the inventor had many serious obstacles to overOne of these was the difficulty of making the cylinder airtight. In the old engines, this was effected by covering the top with water, the dripping down of which into the space below,

come.

where it merely assisted condensation, was of little importance, but, now that the condensation was carried on in a separate vessel, it became highly necessary to prevent any thing entering the cylinder except the virgin steam. The admission of air tended to cool the cylinder, especially in the lower parts, while Watt's great object was to keep it dry and warm, and at an equal temperature throughout. It must be remembered, also, that at this time the top of the cylinder was entirely open; a column of steam thrust up the piston, and the weight of the atmosphere thrust it down again. It now occurred to Mr. Watt that the proper way to effect the object he had in view was to completely close the cylinder, leaving only room for the piston-rod to work up and down. The hole necessary for this purpose was padded with hemp and saturated with oil, so that the natural adhesion of atmospheric air to the piston-rod was wiped away in its descent downward. The next thing was to provide a compensating power for the atmospheric air, whose downward pressure had hitherto been essential to the action of the engine. This he accomplished by introducing a column of steam in the top of the cylinder, so that when the piston had been pressed up by the column from below, it was pressed down again by the column from above, and thus maintained the regularity of its motions by a double-acting steam power. Some minor improvements were afterward added, but what we have described were the radical features of Mr. Watt's first and great reform. The strength, precision, velocity, and controllability of the steam-engine were by these great inventions rendered of practical benefit to the human race. It came into his hands a toy; it left them a mighty instrument of beneficent Progress.

The subsequent improvements made by Watt were equally valuable and astonishing. Like a mighty lion-tamer, he seemed to delight in exhibiting the docility of the brute force he had subdued. "In the present perfect state of the engine,” says Dr. Arnott, in his Elements of Physics, "it appears a thing almost endowed with intelligence. It regulates with perfect accuracy and uniformity the number of its strokes in a given time, counting, or recording them, moreover, to tell how much work it has done, as a clock records the beats of its pendulum. It regulates the quantity of steam admitted to work; the briskness of the fire; the supply of water to the boiler; the supply of coals to the fire; it opens and shuts its valves with absolute precision as to time and manner;

it oils its joints; it takes out any air which may accidentally enter into parts which should be vacuous; and, when any thing goes wrong which it can not of itself rectify, it warns its attendants by ringing a bell. Yet, with all these talents and qualities, and even when exerting the power of six hundred horses, it is obedient to the hand of a child. Its aliment is coal, wood, charcoal, or other combustible; it consumes none while idle; it never tires, and wants no sleep; it is not subject to malady when originally well made, and only refuses to work when worn out with old age; it is equally active in all climates, and will do work of any kind; it is a water-pumper, a miner, a sailor, a cotton-spinner, a weayer, a blacksmith, a miller, etc., etc.; and a small engine in the character of a steam pony may be seen dragging after it on a railroad a hundred tons of merchandise, or a regiment of soldiers, It is the with greater speed than that of our fleetest coaches. king of machines, and a permanent realization of the genii of Eastern fable, whose supernatural powers were occasionally at the command of man."

Watt did not escape the usual experience of inventors, or what Mr. Wilkins Micawber playfully describes as "the pressure of pecuniary liabilities.” His own means were limited, and, in order to prosecute many of his experiments, he had to obtain the assistance of friends. If Dr. Roebuck was one of these, he certainly was a very greedy friend, for he made advances on the hard conditions that two thirds of the profits should be made over to him. Watt's first patent was obtained on these terms (1769). An engine was immediately afterward erected at the doctor's works. It was found to answer tolerably well, but various alterations were needed, and, consequently, a fresh advance of funds was necessary. However willing Dr. Roebuck may have been to assist Watt on the two-thirds principle, he was now unable to do so. He found himself involved in his business, and completely incapable of making farther advances. For nearly five years Watt abandoned the prosecution of his various plans, and sought a living by pursuing the profession of civil engineer. He seems to have waited in expectation of Dr. Roebuck's coming prosperity; but, finding that this was rather a slow process, he resolved to close with a proposal which had been made to him through his friend, Dr. Small, of Birmingham, that he should remove to that town, and enter into partnership with the eminent hardware man