From the last head of the drawing frame, the sliver passes to the fly frame or slubber, which not only continues the drawing and doubling, usually between three pairs of rollers, but through the aid of a device which gives the sliver a slight twist and winds it, for the first time, upon a spindle. This device is known as the flyer, and is, roughly, a U-shaped piece of metal, which, revolving, inverted, over the spindle, gives the thread a slight lateral twist as it coils upon the spindle. The latter also revolves, but with a diminishing motion so that the amount of twist may be kept uniform as the diameter of the coil upon the spindle increases. The sliver, now being twisted, is called a sliver no longer, but the slubbing. The slubbing is passed between the rollers in pairs, the emerging product being less in diameter than the diameter of a single slubbing. The machine combines the fourfold process of combination, attenuation, twisting and winding. There are more spindles upon this frame than upon the slubber. The last drawing frame, except for very fine yarns spun from Egyptian or Sea Island staples, is the roving frame, similar in principle to the last two but containing still more spindles. It receives the rovings from the intermediate frame, combines two of them into one, twists them a little more, and winds them upon the spindle tubes. The Jack frame is similar except that its product is finer and smoother. [Illustration: _Sliver lappers in a Northern mill_] It is interesting to note, however, that the majority of improvements have been the fruit of the brains, not of Americans, but of Englishmen. Copeland points out that this may be due to the English desire to save in the consumption of cotton, but that more probably it is due to the development of fine spinning in England, in which most of the machines here described are chiefly valuable; and he ventures the prediction that now that American mills have definitely gone in for the finer counts, it may be expected that engineers here will apply themselves to the improvement of this machinery. [Illustration: _Drawing frames, turning slivers into roving_] The "Mule" Versus the Ring Spindle Spinning is the final process which turns the cotton into firm, coherent yarn, sufficiently twisted, and ready for the loom. The twist given to the thread by the previous machines has been only enough to make the fibers hold together. They are still comparatively loose and fluffy, and their tensile strength is slight.