The obvious question which suggests itself is, why did not Crompton patent his machine? Some light may be thrown upon this question by considering what was its relation to the jenny on the one hand, and to Arkwright’s machinery on the other, for which, it must be remembered, Arkwright was in possession of full patent rights until 1781. Even the verdict of that year did not legally terminate the rights conferred by his first patent, which continued until 1783. The two bases of Crompton’s “mule” were undoubtedly the principle of the jenny and the principle of the rollers, hence the name. If proof were required that neither the jenny nor Arkwright’s machine produced a completely satisfactory thread for fine work, the demand for Crompton’s yarn in 1780 would supply it. But there was the further consideration that the jenny produced a soft thread which was only really suitable for wefts, while the characteristic feature of the thread spun by Arkwright’s machinery was that it was hard and suitable for warps. One of the defects of Arkwright’s yarn was that it tended to be uneven, and with the rollers there was no satisfactory method of correcting it, though Arkwright attempted to do so by passing the rovings through several machines before they reached the final stage. But the yarn lacked the “stretch” which was given to it by means of the movable carriage which, as we have seen, was an essential feature of the mechanism of the jenny. Crompton’s method was to pass the roving between rollers and then, by availing himself of the movable carriage, to get the “stretch.” Thus he obtained the advantages of both methods, and the result was a thread of much better quality and finer than that produced previously, and it was not only suitable for wefts, but also for warps, particularly for those required in the manufacture of fine cotton fabrics.[364] [Footnote 364: _Souvenir of Royal Visit to Bolton_, pp. 20-21. Baines, _ibid._, p. 197-199.]