The Life of James Watt

"other enjoyments, one of our greatest pleasures is to increase "the hoard. We do not consider that it is already sufficient "for every reasonable purpose. We have acquired a taste "and a habit which we indulge. If you can be amused with "the works of Horace, you will find in them many pleasant "allusions to this folly, and ingenious expositions of the "absurdity of it." We can hardly imagine either a more pleasant allusion to the foible in question, or a more sound exposition of the absurdity of it, than those thus delivered by the amiable and philosophic Doctor; whose discourse sounds partly as a warning against the sin, and partly as a rather complacent confession of its commission.

CHAPTER XIV.

SPECIFICATION OF THE PATENT OF 1769-INTERRUPTED NEGOTIATIONS → CONTINUED EXPERIMENTS- EXPANSIVE POWER OF STEAM-SUCCESSFUL TRIAL OF ENGINE AT KINNEIL PIPE-CONDENSER FURTHER NEGOTIATIONS WITH SOHO-CONTINGENT AGREEMENT WITH DR. ROEBUCK POSITION AND CIRCUMSTANCES OF MR. WATT.

WATT, while continuing his experiments at Glasgow, and his preparations for further trials of the engine "in the glen "behind Kinneil," where "the burn afforded plenty of cold "water" for condensation, and there was greater "freedom "from speculation than about Bo'ness," now busied himself in making a draft of the Specification, which had to be given in and enrolled within four calendar months of the date of the Letters Patent. In the preparation of this document, which afterwards became one of great interest in the history of the steam-engine, not only from the nature of its contents, but also from the long and fiercely-contested litigation of which it was the turning-point, he received the benefit of the advice of his friends Dr. Small and Mr. Boulton; and the event showed that their enlarged views of the principles on which it ought to be framed, were sound and judicious.

"Mr. Boulton and I," writes Dr. Small to Mr. Watt,* "have considered your paper, and think you should neither give drawings nor descriptions of any particular machinery, (if such omissions would be allowed at the office), but specify in the clearest manner you can that you have dis"covered some principles, and thought of new applications of "others, by means of both which, joined together, you intend "to construct steam-engines of much greater powers, and applicable to a much greater number of useful purposes, "than any which hitherto have been constructed; that to

*5 Feb, 1769.

"effect each particular purpose, you design to employ par"ticular machinery, every species of which may be ranged in [one of] two classes: one class for producing reciprocal motions, and another for producing motions round axes. "As to your principles, we think they should be enunciated, (to use a hard word), as generally as possible, to secure you as effectually against piracy as the nature of your invention "will allow. You might declare in some such manner as the following:

"First, you intend that the vessels in which powers of "steam will be employed to work such engines as you may "construct, shall be heated, before the working of the engines "shall begin, at least as hot as the steam to be conveyed into "the vessels, and that this heat of the vessels shall be ren"dered equable, whilst the engines work, by suffering them "to be entered or touched in that time by no substance "colder than the steam they are designed to receive, by "covering them with materials which allow bodies so covered "to cool very slowly, and by proper applications of heated "bodies when they may be wanted. The vessels mentioned "in this paragraph you call steam-vessels.

Secondly, in the engines which you may erect to be "worked, either wholly or partially, by condensation of steam, 66 you intend that the steam shall be condensed in vessels "distinct from the steam-vessels, though occasionally communicating with them. These vessels you call condensers; " and, whilst the engine may be working, you intend to keep "the condensers constantly at least as cold as the air then in "the neighbourhood of the engines, by applications of water, " and other means of cooling heated bodies.

Thirdly, whatever air or other uncondensible elastic vapour may impede the operations of the engines, you "intend shall be drawn out by machines in the manner of pumps, to be worked by the engines themselves.

Fourthly, you intend that on different occasions the necessary steam shall be produced from different substances, "solid or fluid, or partly solid and partly fluid, as may be "most convenient; and also that the vessels in which the

"steam shall be produced, (which you call boilers), shall be "of different forms on these different occasions.

Fifthly, in many cases you design to employ steam in producing reciprocal motions in a manner like to that "in which portions of the atmosphere are now employed in "ordinary reciprocating engines, to wit, by pressing at proper times upon pistons of proper structures.

"Sixthly, to produce by means of steam motions round axes, you intend sometimes to employ reciprocatory joined "to other machines, but more frequently steam-vessels of "forms fitted to different purposes. These steam-vessels will "be mounted on axes, and will contain weights, either solid "or fluid, or partly solid and partly fluid; which weights, or "the centres of their gravity, being constantly, whilst the engines work, pressed by steam beyond planes perpen"dicular to the horizon, and in which planes the axes will "lie, will cause motions of the steam-vessels.

"Seventhly, in these last-mentioned engines, in which "steam-vessels must move round axes, on some occasions you intend to use the condensers described above; but on others, to discharge the steam from the steam-vessels, through proper outlets, into the atmosphere.

"Lastly, to render pistons and other parts of the machinery "air and steam-tight, instead of water you design to employ "paper and pasteboard prepared with oils, oils themselves, or "fat of animals, quicksilver, or melted metals."

Dr. Small adds, in a part of his letter written two days later, "I am certain that, from such a specification as I "have written, any skilful mechanic may make your engines, "although it wants correction; and you are certainly not

obliged to teach every blockhead in the nation to construct "masterly engines." The form of specification thus prudently recommended, differed but slightly from that ultimately adopted, which was signed and sealed on the 25th of April, and enrolled on the 29th of that month.

This letter was accompanied by one from Mr. Boulton,* in

*7 February, 1769.

which he says that Dr. Roebuck had offered him "a share " of his property in the engine, as far as respects the counties "of Warwick, Stafford, and Derby," and then goes on: "I

am obliged to you and him for thinking of me as a partner "in any degree; but the plan proposed to me is so very "different from that which I had conceived at the time I "talked with you upon that subject, that I cannot think it a proper one for me to meddle with, as I do not intend turn"ing engineer. I was excited by two motives to offer you my assistance-which were, love of you, and love of a money-getting, ingenious project. I presumed that your "engine would require money, very accurate workmanship, "and extensive correspondence, to make it turn out to the "best advantage; and that the best means of keeping up "the reputation, and doing the invention justice, would be "to keep the executive part out of the hands of the multi"tude of empirical engineers, who, from ignorance, want of experience, and want of necessary convenience, would be very liable to produce bad and inaccurate workmanship; "all which deficiencies would affect the reputation of the "invention. To remedy which, and to produce the most

profit, my idea was to settle a manufactory near to my "own, by the side of our canal, where I would erect all the "conveniences necessary for the completion of engines, and "from which manufactory we would serve all the world with engines of all sizes. By these means and your assistance "we could engage and instruct some excellent workmen, who "(with more excellent tools than would be worth any man's "while to procure for one single engine) could execute the "invention 20 per cent. cheaper than it would be otherwise "executed, and with as great a difference of accuracy as "there is between the blacksmith and the mathematical"instrument-maker. It would not be worth my while to "make for three counties only; but I find it very well worth "my while to make for all the world.

"What led me to drop the hint I did to you was the possessing an idea that you wanted a midwife to ease you of "your burthen, and to introduce your brat into the world,

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The Life of James Watt: With Selections from His Correspondence