The rnodern mule is oue of the most perfect triumphs of mechanical skill. The processes described above arc entirely automatic, the labour of the attendants being confined to superintend ing : supplying the creel with rovings, piecing the broken threads, doffing the completed Bets, and cleansing and lubricating the whole. In order, however, that the best result's may be secured from the machine, it is necessary that an intelligent supervision should be exercised over it by managers, and great care be displayed by the attendants, ptherwise serious damage can easily be done, and can only he repaired at great cost and trouble. Imperfect adjustment of the spindles and rollers, or neglect to lubricate the spindle footsteps, bolsters, and roller-bearings, or the friction surfaces of the headstock, may soon cause the neglected parts to weal: down, and cause more or less defective action in the parts, greater labour for the attendants, and an inferior product for the result.
Oue of the most important parts requiring attention is the setting of the drawing-rollers in all the machines where they occur. Should the top and bottom rollers of each pair not be set accurately parallel, a great deal of destructive action takes place. In one part, the fibre is overdrawn, strained, broken, or cnt. On the opposite side, where the rollers aro too close, it ie underdrawn and nepped (rolled), the product from the different bosses varying also in counts. The fluted surfaces, and the leather covers, aro also greatly injured, and Boon wear out. Great skill and care have hitherto been required for setting the top drawing-rollers with the acouracy necessary to produce the best result% and these qualities are not always available. As tending to obviate these difficulties, we may draw attention to the recent invention of a roller adjusting gauge, by H. H. Clayton, of Hyde, whose name has already been mentioned in connection with an improved method of lap skewering. By the use of this gauge, rollers may be set with the greatest accuracy and speed by an unskilful person.
The automatic or self-acting mule is not used for numbers of yarns much above 60's or 70'e. When these points are passed, it has been found advantageous to retain the hand mule, which admits of being tempered to exigencies more readily than its rigid mechanical competitor. In spinning fine numbers of yarns, a distinctly different principle is introduced. When the carriage is within a few inches of the end of its traverse, the dravving-rollere stop delivering the roving, whilst the carriage, continuing its traverse, el retches the thread the remainder of the distance. This is for the same purpose as the " gain " of the carriage mentioned in epinning the ordinary counts.
In spinning the finest counts, the ordinary hand mule itself has to give place to a still more sensitive form of the mule, called the " Box Organ." In this mule the arrangement of the parts ie such as to compel the spinner to wait until all tho vibration ceases, before making the different changes. This is requisttc, as the least tremor has a tendency to break dowu the almost invisible threads. This machine is usually employed for numbers above 160'6.
The throstle-frame, as used in cotton-spinning to-day, is a development of the " water-flume" of Arkwright. The latter machine, at the time of its invention, was justly regarded as displaying remarkable ingenuity and merit. In it, the syatem of drawing or attenuating the roving by means
of rollers was Brat made a practical auccosa, and proved so superior to all other modes that, until the invention of the mule, by Crompton, the water-frame stood far above all competitors. After the expiry of Arkwright's patent, the existence of which temporarily prevented the mule coming into use, the latter kept it in check, but never altogether displaced it. The relative superiority, in point of solidity and firmness, of yarn spun upon the water-frame rendered it extremely suitable for warp purposes, and better than could be obtained from the mule. It maintained this position until quite a recent date ; and even now, the best mule-spun yarn does no more than equal it. For producing some descriptions, it is yet esteemed superior to all other machines, and unless Enoch exist in the ring-frame—itself an important moclification of the throstle—it ie held to be without a formidable rival.
The throatle-frame is one of the seriee of bobbin-and-fly frames ; in fact, the parent of the whole. In appearance, it differs little from the roving frame, previously illustrated, except that in detail its parte are smaller, and its spindles are more numerous. 'Ile latter run at a velocity of 3001) 5000 rev. a minute, and are driven from a central shaft, placed within. and extending throughout the length of the machine, and saipplied with driving pulleys at one end of the frame. This shaft carries a long tin cylinder, from which motion is transmitted to the spindlea, by means of endless cotton bande, running upou small wharves on the latter. Each spindle is supplied with a flannel, leather, or cloth washer. On the top of each spindle, is mounted a flier ; and midway, is the bolster rail. When ready for work, each spindle hi supplied with a bobbin—a small short tube with a flange at each end. These flanges differ in shape, the top one being slightly convex on its upper aurface, the bottom one being concave, causing the bobbin, as it were, to stand upon a ring, coinci dent in its dimension with the circumference of the flange which constitutes the base. It is con structed thus, in order to diminish the friction that would otherwise exist. The bobbin fita loosely upon the spindle, and reets upon the cloth washer. The spindle-bolater, in moat frames, is made to traverse up and down a distance equal to the length of the tube of the bobbin, or the apace between the heads. This is called its " lift." In some instances, there is an independent lifting rail. The " ends" or threads having been attached to the bobbine, and the machine having been started, the twist is put in the roving as it cornea from the rollera by the revolution of the spindles, the thread passing through the top of the flier, and then around its leg to the bobbin. The latter, being only in slight contact with the spindle, has a conatairt tendency t,o fall behind it in speed, were it not pulled along by the attached thread. AB, however, the latter is being delivered by the rollers, the bobbin ie permitted to drop behind, so much ea to take up the yarn as it ia spun, winding it upon its barrel or tube. In order that the yarn shall be evenly distributed, the bolster or lifting rail carries tbe bobbin up and down the spindle, which causes the yarn to be wound in even layers.