are tolerably well placed, previous to its operation. If the card cylinders be long, a tightener is used at both ends.

Now with respect to spinning the above substances, the principle of it is founded in, giving to the thread a twisting motion, not only as is usual at either end of it, but at some intermediate point between these ends: which is in fact to twist one end of the thread and untwist the other. This idea is embodied in its most simple form in Fig. 14; where the two pinchers a b hold the thread cd, but without motion; while those e being turned round the thread, untwist the part ƒ of the thread, and increase the twist of the other part g. Now it is evident that the untwisted part is weakened or rendered extensible, while the other part holds so much the stronger together as it is the more twisted. In any machine then possessing the drawing properties, if a thread passes from cylinders having a given motion to others moving faster, and is almost untwisted as it goes, it will give way in the untwisted part, and lengthen in proportion to the drawing tendency.

To perform then this untwisting operation a ring a is used, see Fig. 15, 16, and 17, running on two grooved cylinders bc (or mounted in any other way, so as that the axis of its motion may coincide with that of the thread); the said ring a, carrying two forks ee; and those bearing, on screw points, two light cylinders i k, pressed against each other by a small spring n n n placed at the opposite ends of the forks. By these cylinders the thread is held fast with respect to its circular motions; and if a revolve, it is turned round its axis, being twisted at one end, and untwisted at the other as above mentioned. But this is so ordered, that the twisted part

is always contiguous to the drawing cylinders as ato, Fig. 16.

Thus then if a thread more or less twisted come from p; pass through the feeding cylinders r; the decomposer a (having the required velocity), and also through the drawing cylinders s to the bobbin t; the thread will be untwisted, drawn out and re-twisted as it passes, and be wound up on the bobbin as much longer and finer than' before, as the velocity of the drawing cylinders shall have been greater than the feeding ones. It is almost needless to add that these motions are given by the wheels A B, and the pinions D E, working into the wheels F G, whose number and diameters are in the ratio required by the fineness of the thread, and the degree of twist existing or sought for. It may be proper to observe that the method described is not the only one for performing this untwisting operation. Among many others, the method shewn in Fig. 18, is selected as an example. It is nothing more than three pullies a b c, with or without grooves, placed in the untwisting ring d, over which the thread passes as at 1 2 3, and by the friction of which the operation is performed as before. It is scarcely necessary to add that any method, fit to turn the thread round its axis without obstructing its longitudinal motion, may be usefully employed for the same purpose: this truth is self-evident.

It remains now to describe the new system for this operation of drawing: it consists in performing this operation by the sole friction of the thread round the drawing surfaces, and without that pressure of cylinders which constitutes the usual system. The bodies employed for this purpose are at a small distance from each other, and the thread receives its motion by clinging to their VOL. XIII.-SECOND SERIES.

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unpolished surfaces. In Figs. 16 and 17, this operation of drawing by friction is performed by a number of cylinders 1, 2, 3, 4, 5, placed so as to bend the thread as much as possible; and all having a motion very nearly equal. The thread in passing round them, and being tightened by the counter pull of the bobbins p and t, lays hold of the surfaces both of the feeding and drawing cylinders, and receives their motion respectively. And although this is one method, and a good one of drawing by friction, there are many others which it is needless to describe; one other method is however added in Fig. 18, where a b are two cylinders having both the same motion, placed near but rather obliquely to each other, so that the thread 1, 2, 3, passing from one round the other may not tend to ride upon itself. It is evident that the thread passing two or three times round these cylinders will cling to their surface as before-mentioned, and take the motion they may have received from the rest of the machine.

*

This subject is finished by remarking that, for simplicity, a single system of simultaneous untwisting and drawing has been supposed; but that those systems follow each other to any number, and in any promay portion of velocity, so as to draw down at one passage the largest thread to the smallest size required.

Fig. 19 is the plan of a new kind of chain, calculated to communicate motion from one wheel or machine to another in an uniform manner. The several articulations of this chain as a a, b, are made in the form of a chevron in blazonry, or like a pair of compasses open, and they are intended to take in wheels of which the teeth are formed in like manner. Thus before one link or tooth has ceased to act, the next is already acting; and

for

for this reason there is no interval or inequality of motion. d d d d are the places of some of the centre pins round which the joints turn to permit the bending of the chain.

Fig. 20, is the plan of a chain possessed of the same properties, but with solid links, the chevrons being fixed or cast in relief upon them. These chains are useful in a great number of cases of general machinery, and especially in the communication of equable motion for the operations of preparing and spinning divers filaments.

Fig. 21, offers an useful improvement on spinning machines, arising out of the untwisting system. It is intended to avoid the necessity of always using spindles, and to reel the thread as it is spun. The parts a bare the drawers, and the untwister. d d, e e, are light reels, one for giving, the other for taking the thread. (Or the thread may be taken from a bobbin with or without a twisting motion, and given to the reel, and vice versa, from the reel to the bobbin.) To use this system as here drawn, provide a skain of thread of a certain number or fineness, but twisted more than enough for that number. Then by passing that skain through this system it will be drawn from the reel d d by a, untwisted by c, lengthened by the difference of the motion of a and b; and in fine wound on the reel ee in a state for sale; where note, that the latter reel must have a tendency to envelope all the thread given by the drawer, but not strong enough to break it: this can easily be obtained by friction. And note also, that the reels may be single instead of double, as represented at ƒ g.

In Fig. 22 is shewn the kind of teeth employed for the movements of the wheels, by which the use of cords or strings is avoided in the machinery. The teeth are

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essentially chique or of a seven form. To vatot is functions, and that whether made as desons, & siges in the wheels 4 st this igne The penca si Cent

that the ement of ne cuiqucy be a great or greater tam the dutance between two cognom eet. De axis of two wheels us woring fie tentei sve ail the fretion) must also be in the same piate, frus not understood that a wheel with conque se, iz ir an endless screw, and in which by accident auiter wheel works, or that a wheel whose teeth are mige that those of another wheel situated on antier piove may work into them, makes any part of this inventen. In this instance the obliquity is intended to do away de friction and inequality of action that exists in common wheelwork. As to the section of these teeth it is subject to the same laws as that of common teeth; and sucin is their remarkable properties, that if they wear at all they will give each other the epicycloidal form (ie. to that part of the tooth, that exceeds the calculated diameter); but when that and the division are become perfect by wearing, they will then (supposing the matter hard and the resistance moderated) cease to wear, and last without oil almost for ever, It may be observed also, that the same principle applies likewise to bevel-wheels : and that while, in cylindrical ones, the teeth are threads of a screw of which the functions are suppressed, so in the bevel ones, they are solid helica, increasing in dimensions and distance as they fold obliquely round the surface of a cone.

Having mentioned in the former part of this specification, a machine which twists and draws at the same time, it may be as well now to describe it under one of its forms, for it admits of many.