The full cans from the spread-board are carefully weighed, a given number forming a Bet, which are to be subsequently doubled again into one sliver, for the purpose of eliminating any inequalities that may exist. In the next operation, the sliver from the spread-board passes to the first drawing or "set-frame," so called from the cans containing the sliver being made into "sets" of a certain number, depending upon the number of rows of gills in the " head." These are usually 6 or 8, and as two slivers are put through each row, the number of cans required to form the set is 12 or 16. The set requires to be of a certain weight, and in order to obtain this with accuracy, the sliver-cans are made uniform in weight this being known, they are weighed when full, and the nett weight of sliver in each is carefully marked upon the outside with chalk. The cans from each spread-board are marked with the number of the machine from which their contents have come, and are kept by themselves. When a set is required for one of the drawing-machines, the boy whose duty it is to provide it, selects from the stock of cans those whose weights will exactly make the total required. By this means, any irregularities that may exist in the sliver, owing to variation in feeding the machine, or other causes, are eliminated.
The drawing-frame is very similar in its construction to the spread-board, but is without the revolving apron or leathers, the place of these being supplied by rail and guide-pulleys, as the ribbon-like form of the sliver now requires. The feed-rollers and travelling gills are the same as in the preceding machine, except that the latter are arranged with their pins in a vertical position, whereas in the former, they were slightly inclined in the direction of their traverse. All the parts are finer and proportionately smaller, the work required from them not being so heavy as in the preceding machine.
The function of the drawing-, or 1st set-frame, is to double the sliver from the spread-board, further attenuate it by drawing, and enable the weights to he so regulated as to conduce most perfectly to the attainment of the desired end. In order that this may not be marred, close atten tion is required to all the details, it being especially requisite that care should be taken not to let any "single" pass through. "Single" is the term applied to the sliver, when, from breakage, or exhaustion of the contents of one can, the remaining sliver of the pair continues to pass on alone, so that on emerging at the front, it has only half the required substance and strength. Should this not be detected, it would seriously damage the yarn at the end. When discovered, it is pulled out of the can, or, if it has reached the roving-frame, and gone upon the bobbin, it ie withdrawn from that. Those engaged in tending the machines can easily tell when the faulty portion has been drawn off, by the thickness of the sliver between their fingers. The " single " portion becomes waste, and is put into a receptacle provided for it. There are several causes which operate to pro duce single, besides the above, and in some cases, considerable damage to the gill-pins is also a consequence. Occasionally a fibre or two will lap around the pressing-rollers, and drag others with it, until in a very short time the whole sliver has been turned from its proper course, and wound round the roller, its fellow sliver going forward alone. Sometimes the lap becomes so thick that,
when formed on the inside feed-roller, the gill-pine in rising penetrate it, the consequence being that they are strained or broken, which entails considerable less, owing to the stoppage of the machine and the cost of repairs. Gills are frequently damaged from other causes, which cannot be detailed here. Single, if it has passed the roving-frame, and got upon the bobbin, may almost always be detected through the material upon the bobbin being much softer than the average, owing to its containing much less weight. There is generally attached to each machine an appliance whereby it can be stopped on the occurrence of any unusual strain upon the parts, and if maintained iu good working order, this is usually sufficient to prevent the occurrence of much injury, In each "system," or set of machines that work in success'on to one another, there is the spread-board, and 1st, 2nd, and 3rd, and where a great amount of doubling is required, a 4th drawing-frame. In some cases, the last is omitted, and the sliver is instead put a second time through the 2nd, or other doubling-frame, as may be deemed suitable for the purpose. The latter plan, however, is only adopted when absolutely necessary, because it interferes with the orderly supply of sliver to the succeeding machines, the steed of which it is necessary to reduce, or otherwise allow them to stop. Other means are accelerating the speed of the drawing-frame, thus put to do double work ; or increasing the draft ; or a combination of these. None, however, is so satisfactory as the inclusion of a 4th drawing-frame. These last call for no detailed description, being merely repetitions of the others in every respect, except that the working parts are finer and smaller in proportion.
Booing.—When the material has passed the series of drawing-frames, in which it has been thoroughly opened, cleaned, doubled, and attenuated as sliver, without being twisted, it arrives at the last machine in the preparatory stage of its progress. This is the roving-frame, Fig. 928, a long rectangular machine, similar in its construction to the preceding, so far as concerns the possession of a series of " heads " of gills, traversed from back to front upon spiral screws, but differing in delivering the elongated sliver to revolving spindles, which twist and wind it upon the bobbins with which they are furnished. The roving-frame contains 4-7 heads, each having 8-12 rows of gills. The slivers from the last drawing-frame are passed singly—the doubling being finished— over the rows of gills, and are again further " drafted " in the process. The sliver has now become so attenuated that it is necessary to impart a little twist to it, so as to secure its coherence. This is accomplished by means of the spindle and flier, this machine being one of those belonging to the nume rous group found in nearly all the textile indus tries, and known as " bobbin- and fly-frames." The mechan ism of these having been illustrated and fully described in the article on Jute Manufac tures (p. 1182, Fig. 869), the reader is re ferred thereto for further particulars.