Page:Popular Science Monthly Volume 39.djvu/309

Rh power in 1790, by William Kelly, of Scotland. It was not until 1825 that the self-acting mule was evolved by Richard Roberts. His second patent, dated in 1832, made the self-acting mule applicable to the wool manufacture. But its use continued to be confined, for years afterward, almost wholly to the cotton manufacture. In almost all the American woolen-mills, down to the close of the civil war, the spinning continued to be done on the hand-jack, which is still found in many of them. The introduction of the automatic mule, which became general about 1870, has enormously facilitated the manufacture. It is stated by careful manufacturers that the substitution of the automatic mule, with the other improved machinery which has come during the same period, has resulted in a gain of fully thirty per cent, in production in twenty years. The economical gain, in the saving of help, is even more striking. Experts have calculated the difference between hand-jacks and mules in the cost of manufacture, as follows: Forty-eight cents for one hundred run yarn, with the jack; twenty cents for the same yarn, with the mule, or less than one half.

The hand-jack usually carries 240 spindles, revolving from 4,000 to 4,500 times a minute. Mules carry 300 or more spindles. In the organization of a woolen-mill one set of cards, which requires about twenty-six horse-power to run, will keep from 400 to 500 spindles in motion, although this relationship varies greatly, according to the class of goods manufactured, the age of the machinery, and the capacity of superintendents. American woolen-mills run, in their equipment, all the way from one to seventy sets of cards, and from 240 to 25,000 spindles.

In the woolen manufacture proper, as now conducted, there is but one process after that of carding and condensing to the perfect yarn, ready for the loom. The condensed sliver which has come from the cards is in fact a sort of yarn, which requires only twist and elongation to impart strength, firmness, solidity, and to reduce it to the proper size. The mule has two distinct motions which effect elongation and twist simultaneously. The carriage travels backward and forward, and carries the spindles which hold the bobbins on which the sliver has been wound, while in the frame are fixed other bobbins, called condenser bobbins, to receive the yarn. The machine in operation gives out from small rollers, fixed in the frame, a certain amount of the sliver, simultaneously with the imparting of a degree of twist; then the rollers cease to revolve, while the carriage continues to recede, drawing out the sliver to the necessary length, while in the mean time the spindles, revolving with an increased velocity, furnish what is called the finishing twist. The rollers limit the length of sliver to be operated upon, the carriage draws it, and the spindles impart the twist. This is a very general description of one of the