By the year 1760, the manufacture of cotton goods, which had been increasing slowly from the beginning of the century, had attained considerable importance. In 1764, the declared value of British cotton goods exported was upwards of 200,000_l._, having increased tenfold within forty or fifty years. At this period the demand for them exceeded the supply, in consequence of the difficulty of obtaining a sufficient quantity of yarn for weaving. The one-thread spinning-wheel, now nearly banished from our cottages, was then the sole source from which spun-yarn could be obtained; and the trades of spinning and weaving were commonly united in a humble manner—the man wove, while his wife and daughters spun. If this domestic supply was insufficient, the weaver had often to waste time and labour in collecting materials for his daily work. Mr. Guest states, that “it was no uncommon thing for a weaver to walk three or four miles in a morning, and call on five or six spinners, before he could collect weft to serve him for the remainder of the day; and when he wished to weave a piece in a shorter time than usual, a new ribbon or a gown was necessary to quicken the exertions of the spinner.” This check existing on the industry of the weaver, it is no wonder that mechanical ingenuity was tasked to invent a quicker way of spinning. The principle of the first plan by which this was effected may be easily explained. Suppose a ribbon placed between two horizontal cylinders which are in contact with each other; if the cylinders are made to revolve, it is evident that they will draw the ribbon onwards in the direction of their motion. Again, if the foremost end of it be presented to a second pair of similar revolving cylinders, it will be drawn through these also. If both pairs revolve with exactly the same velocity, it will pass through them unaltered; but if the second pair revolve with greater velocity than the first, there will be a certain strain on the intermediate ribbon, which, if extensible, will be stretched in the same degree that the velocity of the second pair of rollers exceeds that of the first. Now cotton, after being cleaned and carded, comes from the card in fleecy rolls, the fibres of which are laid parallel, and so made fit to spin. To reduce these to thread or yarn takes more than one operation: the first brings the _cardings_ into thick, loosely twisted threads, called _rovings_; the subsequent ones reduce the rovings into yarn fit for the loom. It is evident that both the cardings and rovings are fitted by their texture for the process of extension by rollers described above; and that they would be drawn out twofold, fourfold, or in any greater or less degree, proportionate to the difference of velocity between the first and second pair of rollers. From the second pair the thread is delivered to a spindle, which gives the due degree of twist; and it is finally wound on a bobbin: the whole being set in motion by the same mechanical power.