Chapter III: Preface (3)

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._

SYNOPSIS,
(IN ALPHABETICAL ORDER)
OF THE
_CENTURY OF INVENTIONS_
COMPOSING THIS WORK.

_Note. The objects with Numbers after them are those contained in the present_ PART: _and the Numbers shew the Pages where they stand._

A

1 Adding Machine; or Machine to cast up correctly large columns of
figures.
2 Air Pump; essay towards completing the vacuum.

B

3 Barrel Spring, to lengthen the going of Clocks and other spring-
driven Machines. 26
4 Boats (serpentine) for lessening the expence of traction.
5 Bobbin or Lace (Machine for making) and for covering Whips, &c.
with great rapidity.
6 Bowking Machine for Calico Printers.
7 Bucket Wheels (a combination of) to raise water.