PART FIRST. (continued 2)

This Machine owes its origin to the decree of the French Emperor, for encouraging the making of sugar from beet-root. With the other mechanicians of Paris I was called upon, by a house engaged in that trade, to try my hand upon it; and this Machine was the result. It acts fast and well; and from being less liable to clog, than most of the others, is I believe superior; though this was never proved by any comparative experiment. If it were desired to cut any substance with this machine, the blades would be sharp knives, instead of being toothed; and they would be placed obliquely to the circumference: but the process of grating is that for which it was exclusively designed.

OF A SCREW, With greatly diminished Friction.

My readers will perceive, that I have altered the title given in the prospectus to this Invention. It has been done in deference to the opinions of some persons in high reputation in the mechanical world, who hold that there can be no motion whatever without friction. For my own part I am no believer in several sorts of friction: and must therefore, require a new definition of friction, before I can flow with the stream. As the question, however, is not yet before my readers, I shall wave the discussion at present, and describe this invention, as introducing the rolling motion into the threads of a screw; thus taking away the GREATEST PART of the friction on every supposition.

In Plate 12, fig. 8, A is the screw, and B C the nut, bored large enough to receive the screw, bodily, without any penetration of their threads. Nevertheless, these threads are made to occupy the same length, in both screw and nut, as though they did enter each other: so that the two parts running parallel to each other, leave a square interstice b, all along both nut and screw: into which balls of brass, or soft iron are introduced, which at once restore the screw-property without it’s friction: a friction so considerable in the common screw, that it always surpasses the effective power, since it remains closed, (in a vice for example) while holding any object squeezed with all the force a man can apply. I have mentioned the use of soft balls: it is in order that they may all act together, and work themselves to a common bearing. It will appear by fig. 9, that the acting balls might, or perhaps ought to be, separated from each other by a set of smaller ones; since in this case, the surface of the touching balls move the same way, avoiding all friction between them; and leaving the friction only between those surfaces that are exempt from heavy pressure. These circumstances will be understood by consulting the direction of the arrows in fig. 9; and I have added two other sketches, to shew the principle in it’s application to square threaded screws, as at fig. 10; or to oblong threaded screws, whose threads penetrate each other, in fig. 12. I have further, in fig. 8, sketched one of the methods I propose for supporting the weight of the descending balls, and returning them again into the nut. Considering the balls as a fluid, I have provided a rising column of them, which the working of the screw downward will fill: and the weight of the balls themselves will return them into the nut, when the screw is drawn upward.

OF A SIMPLE AND POWERFUL MICROMETER.

This interesting Machine, see Plate 12, fig. 11, consists of a screw divided into three parts, a, b, c; the first, a, is a mere cylinder to centre the screw at that end: c is a screw of (suppose) 20 threads to the inch; and b another screw of 21 to the inch. D E represents the frame of the Machine, the part E being the fixed nut of the screw C, while the piece f g, forms the moveable nut of the screw C, carrying a finger g, along the graduated bar, E g D. If now, the screw be turned once round by the button H, it will have moved to the left ¹⁄₂₀ of an inch; while the nut and it’s finger g will have progressed on it’s screw ¹⁄₂₁ of an inch to the right: and the difference ¹⁄₂₀ - ¹⁄₂₁ = ¹⁄₄₂₀ of an inch is what the nut f has really moved to the left, along the bar E g D. If therefore, the rim of the button be divided into 100 parts, one of these will represent ¹⁄₄₂₀₀₀ part of an inch by this Micrometer: and I need not add, that this minute portion may be rendered still more minute at pleasure. The means of doing this are evident: It is only making the screws b and c nearer alike in fineness, or number of threads per inch; as 29 and 30, 30 and 31, &c.

I hope it will be understood, that I do not give any of these Machines as the only examples I could furnish of the application of the principles on which they are founded. This very Machine is not a Micrometer only; it might be (if made in proper forms and dimensions) a vice, a press, or other power Machine. It has been already hinted, that change of form must remain to be considered hereafter.

I have chosen to bring forward this Machine at an early stage of the work, because it has, inadvertently perhaps, been ascribed to another person. I refer to an article in the celebrated programme of M. Hachette, of Paris; with which is combined an essay on the composition of Machines, by Messrs. Lanz and Betancourt. In the article D 3, at page 10 of that work, are the following words:

“M. de Prony a trouvé une maniere de transformer le mouvement circulaire, en un autre rectiligne dont la vitesse soit aussi petite que l’on voudra;” and further on—“l’idée en est extremement simple, heureuse; elle est d’ailleurs susceptible de plusieurs applications utiles aux arts.” And in page 11, are these words—“C’est ainsi que M. de Prony est parvenu à une solution aussi simple qu’ingenieuse du probleme qu’il s’etoit proposé.”

For the sake of my English readers, I subjoin a translation of these passages: “Mr. de Prony has found (or invented) a manner of transforming a circular movement into a rectilinear one, of which the velocity shall be as small as may be desired;” and further on “This idea is extremely simple and happy: and is besides, susceptible of several useful applications to the arts.” And in page 11, are these words—“Thus has Mr. de Prony given a solution as simple as it is ingenious, of the problem which he had proposed to himself.”

The above account appears in 1808, and M. de Prony does not prevent or disavow it. Perhaps he had forgotten the circumstance: and perhaps he did not know of this publication: but I solemnly declare that I shewed HIM this Micrometer, executed, fourteen years before! that is, while he and M. Molard were making their report on the Machines proposed for the Water-works at Marly. I certainly wish to accuse no body in this affair: but if I did not state the fact as it is, I should, myself, be stigmatized as a plagiary! I am forced, therefore, to take my stand on the adage—“Fiat justitia ruat cœlum.”

In closing the first Part of this Work, I cannot but express my gratitude for the unexpected degree of support, with which my numerous Subscribers have honoured me. I presume to offer these pages as a fair Specimen of what they may expect in the four succeeding Parts,—namely, as it regards the execution: for the materials of what remains, include objects of greater importance than those preceding. If I have been fortunate enough to raise any favourable expectations in the minds of my present readers, I hope they will express those feelings; and thus induce others to join in bringing to a useful close, a work which is at least intended to produce unmixed public utility. From criticism, I expect candour: and should my intentions, though pure, be misrepresented—should envious tongues or pens assail my labours, or asperse my character, I will defend both, after I can use my Book as my shield—that is, after I have fulfilled my Engagements with my Subscribers: of whom (in expectation of meeting them again within three months) I now respectfully take leave.

J. W.

No. 5, Bedford-street, Chorlton Row.