[Footnote 376: Kennedy, _ibid._, p. 330. In 1788 the writer of a pamphlet estimated that there were at work 550 mule machines of ninety spindles each, and 20,070 hand-jennies of eighty spindles. Aikin, _Manchester_, p. 179.] [Footnote 377: Kennedy, _ibid._, p. 326.] [Footnote 378: Kennedy, _ibid._, 325. Arkwright claimed that he got his first hint of the use of rollers for spinning by seeing a red-hot iron bar elongated by them. Ure, _ibid._, i., p. 271.] II Like the jenny and unlike the water-frame, the mule in its early stages was entirely worked by hand, and was chiefly used in the cottages in country districts.[379] The method of spinning by it soon became well known “from the circumstance of the high wages that could be obtained by those working on it, above the ordinary wages of other artisans, such as shoemakers, joiners, hat-makers, &c. who on that account left their previous employment.... By their industry, skill, and economy, these men first becoming proprietors of perhaps a single mule, and persevering in habits so intimately connected with success, were afterwards the most extensive spinners in the trade.”[380] [Footnote 379: Kennedy, _Rise and Progress of the Cotton Trade_, Manchester Literary and Philosophical Society, vol. iii., second series (1815), p. 127.] [Footnote 380: Kennedy, _Brief Memoir_, p. 335.] It was also by such men that many minor improvements were effected in the mule: “For in the course of their working the machine if there was any little thing out of gear, each workman endeavoured to fill up the deficiency with some expedient suggested by his former trade; the smith suggested a piece of iron, the shoemaker a welt of leather, &c., all of which had a good effect in improving the machine. Each put what he thought best to the experiment, and that which was good was retained.... It would be vain to enumerate all the little additions to Crompton’s original machine; also as they arose so much out of one another, it is impossible to give to every claimant, what is exactly his due for improvements.”[381] [Footnote 381: Kennedy, _Brief Memoir_, pp. 335-336.]