When cotton has been carded, its transformation into yarn consists in gradually attenuating the cotton and twisting it into a thread. In the eighteenth century, the whole process could be definitely divided into two stages. In the first, the carded cotton was made into a continuous but comparatively thick cord called roving; in the second, the roving was attenuated and spun into yarn. The spinning operation was therefore a continuation of the roving operation, and with the ordinary spinning-wheel both were performed in essentially the same way. In spinning, the roving was attached to the spindle, and the spinner with one hand extended the roving, and with the other turned the wheel, which caused the spindle to revolve, and thus gave the necessary twist to the attenuated roving. When this operation had been performed, the spinner, with one hand, again turned the wheel, the spindle again revolving, this time to wind the yarn upon it, while the other hand was engaged in giving in the yarn for the winding. Clearly this system admitted of only one thread being spun at a time. In the invention of the “jenny” the action of that hand of the spinner which attenuated the roving and gave in the yarn for winding was mechanically reproduced, but instead of the spinner being able to operate only one spindle, as many could be operated as could be conveniently introduced. The bobbins round which the rovings were coiled, and the spindles, were fixed in a frame. The ends of the rovings were attached to the spindles, passing between a clasp arrangement which formed part of a movable carriage. While the clasp was open, the carriage was first drawn out from the spindles until the required length of rovings for spinning had passed through. Then the clasp was closed, and the rovings, thus gripped, were attenuated by the carriage being drawn further out. Simultaneously, the wheel, which caused the spindles to revolve, was turned to give the required twist to the thread. Then, as the carriage was moved back to its first position, the wheel was again slowly turned, this time to wind the spun thread on the spindles. Thus the action of one hand of the spinner remained the same, but the other was now used in opening and closing the clasp and in moving the carriage to and fro.