That portion of a "self-actor mule" which guides the faller wires is termed the "shaper" or "copping motion." It consists of an inclined iron rail upon the upper smooth surface of which slides the "copping bowl," this being a portion of the mechanism which connects the rail with the faller wires. The rail rests upon suitable inclines termed "copping plates," whose duty it is to regulate the movement of the rail so as to allow for the ever-increasing dimensions of the cop during the building process. When the carriage again reaches its initial position, suitable mechanism causes all the parts to return in the position required for spinning. Such is the complete cycle of movements of the "mule," each succeeding cycle being simply a repetition of the preceding. It will probably take such a mule as the one described about six hours to make a "set of cops," _i.e._, one on each spindle, each cop being 1-1/4 inches in diameter and 7-1/2 inches long. Every fifteen seconds, while the mule is making a cycle of its movements, may be divided up approximately as follows: nine seconds for the drawing-out and twisting; two seconds for backing-off; four seconds for winding-on and resuming initial position. A multitude of minor motions and details might be easily expanded into several chapters; in fact, more can be said about the mule than about any other spinning machine, but such detailed description would be out of place in this story. All the motions just named are centred in what is termed the "Head Stock," this being placed midway in the length of the mule. This head stock receives all the power to drive the various motions, from the shafting and gearing, and distributes it in a suitable manner to various parts of the machine. It will have been observed by this time, that, as in the case of the bobbin and fly frames, the intricate and wonderful mechanism of the self-actor mule is not devoted to the formation of threads, but to the effective and economical placing of the threads of yarn, in the form of cops, after it has been spun. Image: FIG. 29.--Mule head showing "copping rail." The spinning processes take place during the outward traverse of the mule carriage, the mechanism involved in this motion being comparatively simple. The really complicated and difficult motions being "backing-off," revolving the spindles "during winding-on," and the guiding of the spun threads upon the spindles during the winding-on process. It was the addition of these three motions by the later inventors which gave the mule the title of "Self-Acting." CHAPTER X. OTHER PROCESSES IN COTTON SPINNING.