The motions of the various parts of the engine are given as follows. Upon the end of the machine, represented in [fig. 975.], there are attached to the shafts E ([fig. 976.]), the bevel wheels 1 and 2, which are set in motion by the bevel wheels 3 and 4, respectively. These latter wheels are fixed upon the shaft m, [fig. 975.] m is moved by the main steam shaft which runs parallel to it, and at the same height, through the length of the engine apartment, so as to drive the whole range of the machines. 5 is a loose wheel or pulley upon the shaft m, working in geer with a wheel upon the steam shaft, and which may be connected by the clutch n, through the hand lever or geering rod o ([figs. 975.] and [976.]), when the engine is to be set at work. 6 is a spur wheel upon the shaft m, by which the stud wheel 7, is driven, in order to give the traverse motion to the guide bar H. This wheel is represented, with its appendages, in double size, figs. 979. and 980., with its boss upon a stud p, secured to the bracket q. In an eccentric hole of the same boss, another stud r, revolves, upon which the little wheel s, is fixed. This wheel s, is in geer with a pinion cut upon the end of the fixed stud p; and upon it is screwed the little crank t, whose collar is connected by two rods u ([figs. 975.] and [976.]), to a cross-piece v, which unites the two arms w, that are fixed upon the guide bar H, on both sides of the machine. By the revolution of wheel 7, the wheel s will cause the pinion of the fixed stud p to turn round. If that wheel bear to the pinion the proportion of 4 to 1, then the wheel s will make, at each revolution of the wheel 7, one-fourth of a revolution; whereby the crank t will also rotate through one-fourth of a turn, so as to be brought nearer to the centre of the stud, and to draw the guide bar so much less to one side of its mean position. At the next revolution of wheel 7, the crank t will move through another quadrant, and come still nearer to the central position, drawing the guide bars still less aside, and therefore causing the bobbins to wind on more thread in their middle than towards their ends. The contrary effect would ensue, were the guide bars moved by a single or simple crank. After four revolutions of the wheel 7, the crank t will stand once more as shown in [fig. 980.], having moved the bar H through the whole extent of its traverse. The bobbins, when filled, have the appearance represented in [fig. 982.]; the thread having been laid on the mall the time in diagonal lines, so as never to coincide with each other.
Doubling is the next operation of the silk throwster. In this process, the threads of two or three of the bobbins, filled as above, are wound together in contact upon a single bobbin. An ingenious device is here employed to stop the winding-on the moment that one of these parallel threads happens to break. Instead of the swifts or reels, a creel is here mounted for receiving the bobbins from the former machine, two or three being placed in one line over each other, according as the threads are to be doubled or trebled. Though this machine is in many respects like the engine, it has some additional parts, whereby the bobbins are set at rest, as above mentioned, when one of the doubling threads gets broken.
[Fig. 983.] is an end view, from which it will be perceived that the machine is, like the preceding, a double one, with two working sides.
[Fig. 984.] is a front view of a considerable portion of the machine.