We therefore set aside that part of the apparatus or machinery, and allowed the mule to stop in the common way, on receiving the full complement of twist; and the instant it stopped, the boy or girl, without putting their hand to the fly-wheel, just turned the guide or faller with the hand, which instantly set in motion the spindles, and took in the carnage, the cop being shaped by an inclined plane, or other contrivance.....It may naturally be asked, Why were not the self-acting mules continued in use? At first, you know, the mules were about 144 spindles in size, and when power was applied, the spinner worked two of such; bat the size of mules rapidly increased to 300 spindles and upwards, and two such wheels being considered a sufficient task for a man to manage, the idea of saving, by spinning with boy3 and girls, was thus superseded." So numerous and diversified have been the successive improvements in this important branch of art, that a very large volume might readily be filled with merely a selection of the more ingenious; but our prescribed limits compel us to confine our present notice to the most successful, and we believe the most perfect mechanism for spinning hitherto brought into use, which is the self-acting mule, invented by Mr. Roberts, of the firm of Sharp and Roberts, of Manchester. The following description of the invention, extracted from the patentee's specification, we copy from the London Journal of Arts and Sciences, Vol. VIII. Second Series.

"The nature of my said invention consists of an improvement or improvements in the mechanism employed to render self-acting the machines commonly known by the names of mule, billy, jenny, jack-frame, stretching frame, and all other machines of that class, whether used to rove, slub, or spin cotton, or other fibrous substances, the particular object of which improvement or improvements is to effect in a more complete manner than has hitherto been done by self-acting machines of the kinds above mentioned, the regular winding on of the yarn, or roving, upon the spindles, by regulating their rotatory motions according to the gradually varying form and increasing diameter of the cop. In Figs. 1 and 2, a a is a mule carriage in two parts, one on each side of the headstock, the parts being firmly united by b b, a connecting bar of iron, and c c, an iron frame; to this is bolted in front a frame of iron d, which at its upper part, is supported by e, a spur piece, bolted to the bar b and to the frame d.

On studs in the spur piece arefftwo ratchet tension barrels; to one of these is fastened g a cord, which, after passing over a notch in the spur piece e, is wound round and fastened to h a drum or barrel; this has also attached to and coiled round it t another cord, which after passing over j a guide pulley, and a notch in the spur piece, is attached .to the other ratchet barrel. A shaft k, on which is keyed the drum h, has a pinion l working into m the toothed quadrant, which receives an alternating motion on its centre, through an arc of about 90°, whilst the carriage runs out and in, that is to say, at every stretch. In a groove in the inner arm of the quadrant is n a sliding nut moved by o a double threaded leading screw, on the lower end of which is keyed p a mitre wheel, gearing with q another mitre wheel, the central stud of which is opposite to the centre of the quadrant. Attached to the back of mitre wheel q is r, a pulley, which is turned at intervals by s an endless strap passing round it, and t a sliding pulley. A weighted lever w, called the governor lever, is movable on a stud in the back part of the carriage frame, and forms the upper jaw of a pair of pincers, the lower jaw being v a stud in the carriage end.

The lever u, when not intended to press upon the stud v, is carried by an adjustable nut on the lower end of w, a rod connected with the arm of the counter fuller, and having free play through a hole in a side projection from the arm of the lever. When, in winding on, the tension of the yarn brings the faller wires to nearly the same level, the dropping of the arm of the counter faller allows the lever u to descend till it pinches the endless strap s against the stud, and drags it along as the carriage runs in, until the rise of the counter faller arm again raises the lever and liberates the strap. The spindles are banded in the ordinary way, and the drums are driven by a band, which, after taking both the grooves in x, the driving pulley, is spliced, instead of passing from the carriage to the twist pulley, as in common mules. The pulley x is keyed on y, an inclined shaft, the upper end of which turns in a swivel collar, and the lower end or foot in an arm of a bell crank. During the process of twisting and backing off, the shaft y receives motion through 1, a mitre wheel, which is keyed near its lower extremity, and is driven by 2, another mitre wheel fixed on 3, a shaft, on which is also keyed 4, a double grooved driving pulley, receiving motion by an endless band from 5, the twist pulley above.

This pulley band passes under a carrier pulley, and over a double grooved carrier pulley, under the driving pulley 4, again over pulley 7, and under pulley 4, round 8, a sliding carrier pulley, under 9, a carrier pulley, and thence to the twist pulley. The mitre wheel 1, comes occasionally into gear with 10, another mitre wheel, keyed on 11, a shaft, upon which is also keyed 12, a spur wheel, which gears into 13, another spur wheel, firmly connected to 14, a drum or barrel, which is called the winding-on barrel. The diameters of wheels 12 and 13 should be made to give, as nearly as possible, the proper amount of rotation to the spindles, according to their diameters and those of the warves, the final adjustment being made in the diameter of the barrel 14, the whole being adapted to give so much motion to the spindles as will cause them to wind on the whole stretch at the first run in. There is a cord 15, one end of which is tied to the sliding nut n in the arm of the quadrant m, and the other made fast to the barrel 14, after having made several coils round it; and 16 is an opposing cord, also coiled round and fastened to the barrel 14, and after passing under 17, a carrier pulley, and over 18, another carrier pulley, it sustains 19, a counterpoise, which causes the barrel 14 to take up the cord 15 as the carriage recedes from the rollers.