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loss by friction. But another obstacle was about to be thrown in the path of progress, and which at one time bade fair to utterly ruin Watt's prospects of receiving a pecuniary reward for his great labours: this was the bankruptcy of Dr. Roebuck. "The coal-fields of Kinneil, instead of throwing a golden shower of profits into his lap, were the means of bringing him to ruin. The quality of the coal was far beneath his expectations; and the difficulties of getting even an inferior produce daily increasing, he was necessitated, from the drain on his capital, to part with, from time to time, his share in other lucrative concerns with which he was connected: and thus, by degrees, the very perseverance which distinguished him in better times, tended, by its prompting him to preserve in this instance the wreck of his once great fortune, to sink him still further into difficulties, until at last irretrievable ruin overtook him; and he was obliged to enter into a negotiation to give up his connexion with Watt, from which he might have reaped a harvest greater than he had gathered from all his previous projects, lucrative as they were, put together. But this apparently untoward circumstance was the means of ultimately placing Watt in the eminent position which he afterwards occupied; so true, as we often find it, is the saying, that “man's extremity is God's opportunity.”

The party with whom Roebuck negotiated for a transfer of his rights in the patent of Watt, was the celebrated Matthew Bolton, of Soho, near Birmingham; a man whose name will always be handed down to posterity in conjunction with his more celebrated compeer. The transfer was effected, and a partnership formed between Bolton and Watt. In character the very opposite in many respects of Watt, Bolton was possessed of rare business talents, an extensive acquaintance with business forms, and having that indomitable spirit of “perseverance which insures success” in an eminent degree; these, united with a degree of courage in prosecuting his engagements in the face of difficulties, rendered him a fitting coadjutor for the retiring and unambitious Watt. “ To a man like Watt,” says an able writer, “ so unfitted, from feeling and habit, to stand alone, nothing could have been more auspicious than his gaining the protection of two such men in succession (as Roebuck and Bolton). Obstacles were seen by either only to be surmounted; and they both possessed, in an eminent degree, the master-art of infusing into all around them a portion of their own matchless energy. Projectors themselves, they were considerate of his feelings, and knew how much the flow of thought in irresolute or hesitating genius is quickened by the kindness and condescension of a patron. Assisted by their experience, and animated by their generous approbation of what he had already achieved, he was roused and carried onward to impart greater perfection to his mechanism.”

At the period of the transfer of Roebuck's rights in the patent to Bolton, Watt was engaged in surveying in the north of Scotland. Shortly after the death of his wife happening, he was induced to accept of the invitation of his partner, and to take up his abode at Soho. This now celebrated locality, at the time of Bolton's purchase of it, is described as a “ barren heath, on one black summit of which stood a naked hut, the habitation of a warrener.” A little iron mill was subsequently erected, and round the hill there rippled a small stream. Bolton, with the quick perception which distinguished him as a man of business, saw at once the superior advantages which it held out as the site of a manufactory for the

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fabrication of those articles for which Birmingham has been so long famed. By collecting the water, he obtained sufficient quantity to move the waterwheel, which, in its turn, gave motion to an almost endless variety of manufacturing machines and tools.

Watt was now in a position for prosecuting his labours with vigour, and surrounded by those mechanical appliances; without which the attainment of perfection in the working details was hopeless. An engine was accordingly erected; and many Cornish adventurers, greatly interested in the success of the engine, on invitation, examined its operation. In their report they gave a favourable opinion as to the saving of fuel effected by it. Some

years of the term for which the patent was valid had, however, expired; and fearful that its whole period would pass over before pecuniary results accrued, so as to afford a profit, or to reimburse the large expenses which had been gone to in perfecting the engine, Watt, at the suggestion of Bolton and his other friends, applied to parliament for an extension of his patent. This, after some opposition, was granted for the term of twentyfive years, dating from the time of the grant, namely 1775. This extension was no doubt deserved, no less a sum than 50,0001. having been expended in the manufacture of the engines by the firm before any return was realised. Having thus secured for a lengthened period the profits which might accrue from the sale of the engines, Watt was now in a position to introduce his machine with every advantage to the public. In this he was materially assisted by the admirable commercial arrangements of Bolton, who, after the grant of extension, became a partner with Watt in the manufacture of the machines; thus sharing the profits on this head, as well as those derived from a monopoly of the principle.

“ Had Watt, says Playfair, “ searched all Europe, he could not have found another man so calculated to introduce the invention to the public in a manner worthy of its importance."

The most public and open inspection of the engines at work was invited, and every means taken to afford just opportunities of ascertaining their value. A congress of mechanics and scientific men was convened' at Soho, and an elaborate series of trials made and comparisons instituted between its working capabilities and one on the principles of Newcomen of the best construction, in order to show the superior working capabilities of the new engine: these were manifest to all. But still further to place the merits of the machine on a basis which would satisfy all as to the character of its claims, the patentees issued the following: “All that we ask from those who choose to have our engines, is the value of one-third part of the coals which are saved by using our improved machines, instead of the old. With our engine, it will not, in fact, cost you but a trifle more than half the money you now pay to do the same work, even with one-third part included; besides an immense saving of room, water, and expense of repairs. The machine itself which we supply is rated at that price which would be charged by any neutral manufacturer of a similar article. And to save all misunderstanding, to engines of certain sizes certain prices are affixed.” To aid in the introduction of the new machines, Bolton and Watt took old atmospheric engines off the hands of those who wished to lay down the improved form, and this frequently at a rate above their value.

Again, in estimating the power of their engines, or calculating the work which each could perform, Bolton and Watt, instead of placing the estimate

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of a horse's work at a low figure, and thus in the same proportion increasing the power of their engine, they actually increased the power of a horse's work to one-third. Smeaton had valued the work done by a strong horse as equal to lifting a weight of 22,000 pounds one foot high in a day; Bolton and Watt estimated at 33,000. But more than this, they stated that their engines were “calculated so, that they will raise 44,000 pounds one foot high with a bushel of coals; and when we say our engines have the force of five, ten, or more horses, we mean and guarantee that they will lift 44,000 pounds for each horse-power.” On these terms, an engine which, according to Smeaton's estimate, was equal to twenty horses, was, according to Bolton and Watt, only equal to ten; thus giving the purchasers of the new engine an advantage of 100 per cent in value for no increase of cost.

Thus placed before the public on terms so highly liberal, the invention made rapid progress in public favour; and some idea of the profits accruing may be derived from the fact, that at Chacewater mine, Cornwall

, the saving of fuel effected was equal to 60001. annually; 20001. of revenue from this one source being drawn by the firm.

The manufacture of the engines increased with such rapidity, that the original establishment at Soho was found too limited in its dimensions for the great quantity of work now flowing into the factory. Another was therefore constructed in the near neighbourhood, in which the operations could be carried on with a high degree of concentration, iso essential to the turning out of work rapidly and efficiently. “We are," writes Bolton to

" the celebrated Smeaton, “systematising the business of engine-working ; we are training workmen, and making tools and machines, to form the different parts with more accuracy and at a cheaper rate than can possibly be done by the ordinary methods of working. Our workshops will be of sufficient extent to execute all the engines which are likely to be 'soon wanted in this country; and it will not be worth the expense other engineer to erect similar works, for that will be like building a mill to grind a bushel of corn." The expenditure thus occasioned to the firm was not thrown away: a body of expert workmen was soon organised.

Having thus brought up our historical notes in connexion with Watt's engines to the contemplated point, we are prepared to proceed to the illustration of the successive steps of his invention, and of those beautiful contrivances which emanated from his mind.

The diagram in fig. 20 will illustrate the arrangements of parts of the early engines introduced by Watt for pumping the water from mines. Let a be the cylinder, in which the piston b works a rod passing through a steam-tight stuffing-box c; the cylinder is surrounded by an external casing dd, into the space formed by which the steam enters from the boiler through the pipe e. By opening the valve e, the steam is introduced to the pipe beneath the cylinder, and introduced into its interior through the aperture f. By opening the valve g, the steam is allowed to pass down to the interior of the condenser h. In this diagram the piston-rod is supposed to be attached to the end of the great beam which works the mine-pump, and the valves to be worked by mechanism, which we shall figure afterwards.

Before starting the engine, the air was extracted from the various parts. This was effected by opening the valves, and allowing the steam to flow into all the vessels and pipes; the air is thus forced down the pipe to the condenser h, and through the valve which connects this with the air-pumpj.

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The valve e is then shut, thus preventing more steam from entering the cylinder a through the aperture f; at the same time the steam in the condenser h is condensed by the cold water which surrounds it, and supplied to the cistern mm, in which it stands, by the spout n, supplied by a common force-pump worked by the great beam. The vacuum being thus formed beneath the piston b, the pressure of the steam, which has free access to the upper side of the piston, forces it downwards to the bottom of the cylinder. By the action of the beam, the air-pump piston is pulled upwards, and the water withdrawn from the condenser h. By the valve mechanism, the valve g is shut, and the valve e opened ; steam is thus introduced beneath the piston, and an equilibrium being established between both sides, the counterpoise at the end of the great beam draws up the piston to the top of the cylinder ; the air-pump is thus depressed, and the portion of condensed water lying in the lower part of the barrel passes through the clack or valve in the piston ; the mechanism of the valve then shuts the valve e, and opens g; this taking place on the piston a reaching the top of the cylinder, the steam below the piston rushes through the valve g to the condenser, and a vacuum being formed as before, the piston is forced by the pressure of the steam on its upper side towards the bottom of the cylinder. The opening and shutting of the valves e and g was effected by simple mechanism, as follows.

Let a, fig. 21, be the spindle of the valve admitting steam to the cylinder, and b that of the valve admitting the steam to the condenser ; these are connected by a joint to levers moving on the centres cc; hh is the

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plug-frame, having studs or projecting pins o n; these strike the handles or levers which are fixed on the rod ii, and to which the levers rp are fixed,

actuating the levers de, and lifting or depressing the valves ab; s is the counterbalance weight which acts the tumbling bob in Beighton's valve gearing already noticed. The condenser, in its original form as introduced by Watt, consisted of a series of thin copper pipes communicating with each other, and placed in a cistern filled with cold water: in some instances flat copper pipes were used; the object, in

both cases, being to present as great d 19

a surface as possible to the action of the cold water, and to effect a rapid condensation. Notwithstanding many drawbacks attendant upon this plan, it was considered an economical one,

inasmuch as a comparatively small fig. 21.

power was required to work the pump

for withdrawing the air and condensed water. To receive a quick condensation by this method, it was indispensable to have a large amount of surface exposed to the cold water; this necessitated condensers of such size, that Watt was at last obliged to return to a plan which he had adopted while in Scotland during his trials under Roebuck, of condensing the steam by introducing a jet of cold water into the co iser. The clumsy outer casing was, after repeated trials, found to be possessed of inconveniences; Watt therefore discarded it, and adopted a plan of intercasing composed of thin sheet-iron, the space being only one inch and a half between it and the cylinder; this space was supplied with

steam by a pipe leading from the main steampipe. This arrangement involved a radical change in the method of distributing the steam to the cylinder. The details of the new construction may be gathered from the diagram in fig 22.

Let aa be the cylinder, bb the outer casing, c the piston, d the piston-rod, e the steam-pipe leading from the boiler, f the “steam-valve,"g the "equilibrium-valve," and h the "eduction-valve" in the pipe leading the steam to the equilibrium-valve. Supposing the piston at the top of the cylinder, the equilibrium-valve is closed, and the steamvalve f and eduction-valve h opened; the steam from below the piston rushes through h to the condenser, and a vacuum is formed ; the steam press

ing on the upper side of the piston, it is forced 1 downwards. On reaching the bottom, the steam

valve f and eduction-valve h are closed, and the fig. 22.

equilibrium-valve g opened; this allows the steam to gain access to the under side of the piston, as

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