Page images
PDF
EPUB

How was

“ water, that vessel must condense a large quantity of steam " whenever it was attempted to be again filled with steam ; " that the vacuum could not approach to perfection without “ the steam was cooled below 100°; and that such cooling “ would increase the evil complained of in a fourfold or “ greater ratio, because the penetration of the heat or cold “ into the cylinder would be as the squares of the differences “ of the heats between that vessel and the steam. “ this to be avoided ?

“ He tried to make the cylinders of wood or other materials “ which conduct heat slowly, but he could not prevent the “ steam from coming into contact with the comparatively “ cold water which remained in the bottom of the cylinder, “and which must be expelled by the steam; besides, his “ wooden cylinders did not seem likely to be of long duration. " In such-like experiments he spent much time, and more “ money than was suitable to his circumstances, yet he made “ no advances towards a beneficial discovery. But the matter “having got firm hold of his mind, and his circumstances “ obliging him to make exertions to regain what he had spent, “ he turned the matter over in every shape, and laid it down “ as an axiom,—that to make a perfect steam-engine, it was necessary that the cylinder should be always as hot as the steam which entered it, and that the steam should be cooled down below 100° in order to exert its full powers. The gain " by such construction would be double :--first, no steam “ would be condensed on entering the cylinder; and secondly, " the power exerted would be greater as the steam was more “ cooled. The postulata, however, seemed to him incom“patible, and he continued to grope in the dark, misled by

many an ignis fatuus, till he considered that steam being “ an elastic fluid, it must follow the law of its kind; and " that if there were two vessels, A and B, of equal or other “ dimensions, the one, A, filled with steam, and the other, B, “exhausted, if a communication were opened between those “ vessels, the steam would rush from the full one into the "empty one, and they would both remain half exhausted, (if " the vessels were equal in size), or be filled with steam of

“ half the density. If, then, into the second vessel, B, an

injection of cold water were made, or cold water applied to “ its outside in sufficient quantity, the portion of steam which it contained would be condensed or reduced to water; and " by the same law of nature that had operated before, more “ steam would issue from A into B until the whole was con

densed, and nearly a perfect vacuum established in both “ vessels; yet as the cold water had not entered or touched “ A, that vessel would still retain its heat.

“ This idea once started, the rest immediately occurred. “ The vessel A being supposed to be the cylinder, B would “ be the vessel called now the condenser; the water, air, &c., " accumulated in B, he immediately saw could be discharged

or drawn out by means of a pump, or the water might be “ let run out by a pipe more than 34 feet long going down

wards, and the air might in that case be expelled at a valve “ by filling B with water, provided the descending eduction

pipe were shut meanwhile. On the whole, however, he

preferred the pump. Another difficulty appeared, which “ was the making the piston tight. That could not be done “ with water, as in Newcomen's engines; for that might get “in and evaporate, and produce steam. He therefore thought of wax, oil, and similar substances, as substitutes, knowing " that they would not evaporate in the heat of boiling water ; “ and, for greater security, he proposed to employ the steam “ itself as the acting power on the piston.

“ The diameters of the pipes necessary to convey the steam “ into and out of the cylinder, he regulated from those in use. “ The size of the condenser he assumed at random, as he did “ that of the air-pump, which it was evident must be larger “ than was necessary to contain the water and probable quan

tity of air. All this passed in his mind in the course of a “ few hours; and in a few days he had a model at work, with “ an inverted cylinder, which answered his expectations, and “ was, as far as he remembers, equal in its properties of "saving steam and fuel to any he has made since, though “ in point of mechanism much inferior. Very simple cocks were employed as regulators or steam-valves, and his airpump and condenser were of tin-plate. His cylinder, how

ever, was good, and of brass, [about] 2 inches diameter and “a foot long; the cocks were turned by hand instead of being “ wrought by the engine.

“ If Mr. W. is thought worthy of credit in this matter, and " the facts are consequently allowed, where was the mighty

difficulty of putting the invention in execution from still “ fewer data than he has set forth in his specification ? He “ is not so presumptuous as to think that there were not, and “ are not, numbers of mechanics in this nation, who, from the “ same or even fewer hints, would have completed a better “ engine than he did. Mr. Bramah has proved* that he “ could, and W. is inclined to believe him. But W. does not “ pretend that any body could have done it without thinking

upon it, nor without much previous knowledge and some experience of similar things. “ Had W. been content with the mechanism of steamengines as they then stood, his machine might soon have s been brought before the public; but his mind ran upon

making engines cheap as well as good, and he had a great “ hankering after inverted cylinders and other modifications “ of his invention, which his want of experience in the prac“ tice of mechanics in great,f flattered him would prove more “commodious than his matured experience has shown them “ to be. He tried, therefore, too many fruitless experiments “ on such variations. He wanted experience in the construc" tion of large machines; that he endeavoured to acquire ; “ but experimental knowledge is of slow growth, and with all “ his ingenuity, 80 much boasted to his prejudice, he was con“ cerned in making some very indifferent common engines. “ Other avocations, to him necessary, obliged him to turn his “attention from the subject till he obtained the patent, so “ that at that time he had made no advances in the improve“ ment of the mechanism. He therefore thought it proper

i.e. Given it in evidence.

ti.e. On a great scale.

[ocr errors]

s to specify only what was his invention, and to leave any “ mechanical improvements he might make, to be secured by “ other patents, if worthy of them.

“ His idea, then, was to apply his invention to the steamengines as they existed. For this purpose there was nothing “ else necessary than to shut up the snift, to apply a regulator

or valve to the opening of the eduction-pipe within the “ cylinder, an air-pump to the outer end of that pipe, and to “ inject into the upper end of the eduction-pipe. If, at the

same time, the cylinder was defended from the cold of “ the atmosphere, the engine would thus be complete, if the

weight of the atmosphere were to be employed as the

acting power; for all the regulators could be easily opened “ and shut by the then existing contrivances, and the airpump rod could be suspended from the working beam. “ If, however, the engine was wanted to receive all the advantages of the invention, the cylinder was to be placed “ in a case containing steam, with access for that fluid to the

upper side of the piston, so that it might act upon it as the “ atmosphere acted in common engines, or in the case just “ stated. And in this latter manner were the engines made " which he constructed in the beginning of the business ; that " is to say, the cylinders were fixed in a case containing

steam, with which fluid they were wholly surrounded; and, “ their mouths being open within the case, the steam had

always access to the upper side of the piston, and was “ admitted to the part below the piston only when the piston

was rising. The opening from the cylinder into the educ

tion-pipe was shut by a valve while the piston was rising, “ but when it was required to descend, the valve was opened. “ Those valves were of the sliding kind used in Newcomen's

engines. The injection was made into the eduction-pipe; " and the air-pumps, which drew out the water as well as the “air, were fixed to the bottom of the eduction-pipe, which “ had a valve to prevent regress as usual. There was some“ times one pump, and sometimes there were two or three, as “ circumstances or the fancy of the moment directed. The “ working beams and working gear were made in the usual

[ocr errors]

“ manner, or nearly so; and in cases where there were boilers “ fixed for the common engine, which was superseded, they “ were used without alteration.

These engines, then, differed in nothing from the ancient

ones, except in the application of W.'s principles as set “ forth in his specification.

“ It was found that the external cylinder, or steam-case, was very expensive. The method of covering the cylinder

itself with a lid or cover, (which had been used in some of “ the models), and conveying the steam to the lower end of “ the cylinder by a pipe, was adopted, and a less expensive “ method of applying the envelope of steam was used. Other “ kinds of regulators were invented, and the whole mechanism “ of the engine was gradually improved, and these improve"ments have been progressive for the last twenty-one years. “ Some of them W. has secured by other patents, but many “ of the most essential he has left free, and by means of them “ Newcomen's engines have been improved to his loss.

“ It will now, it is hoped, appear to the candid that W. has “ not wilfully concealed his invention by a false specification, “ but has set forth the nature of the same, and the means of “ performing it. He has told what he had invented; and it “ could not have been expected that he should have described “ mechanism already known to all practitioners, or not then “ invented.

“ W's invention is merely a contrivance to prevent cooling " the cylinder, and to make the vacuum more perfect by con

densing the steam in a vessel distinct from the cylinder itself ; “ this is the nature of the invention. The means of keeping " the cylinder warm,—the substitution of the powers of steam “ for those of the atmosphere,—of grease, &c., in place of “ water to keep the piston tight,-and the drawing out the “ air, &c., by means of pumps, are merely aids in performing " the principal object. This ought to be kept in view in “ judging of the specification; also that W. supposed it to “ be addressed to mechanics and philosophers, and not to the “ignorant."

« PreviousContinue »