Sufficient has been said in the previous chapter to indicate the place which Crompton’s invention occupied in the development of the cotton industry during the latter years of the eighteenth and the early years of the nineteenth centuries. A striking thing was the rapid increase in the size of the machine, particularly after 1790. The first mule constructed by Crompton contained only 48 spindles; in 1795 the smallest mule made by M‘Connel & Kennedy appears to have had 144 spindles. In February of that year a correspondent was informed “in respect to what number of spindles may be most profitable, it is difficult to fix, as what was thought best only two years ago is now thought too small.... We are now making from 180 to 288 spindles.” Three months later, in reply to another correspondent, it was stated that most of the mules were then made to go by steam or water, and in the next year we find them supplying mules to work in pairs, the two containing 372 spindles. In 1799 they were making single mules with 300 spindles, and in the same year Dobson & Rothwell were making them with 408 spindles.[487] When Ure published his _Cotton Manufacture_ in 1836 the largest mules then in use apparently contained somewhat over 500 spindles. At the present day they are made to three times the size, a pair of mules containing 2000 to 2500 spindles being common. [Footnote 487: Dobson, _ibid._, p. 112.] But in addition to enlargement the mule as invented by Crompton has, of course, undergone vast improvements. As we have seen, movements originally performed by hand soon came to be performed by mechanical means, the culmination of this kind of improvement being reached in the invention of the “self-actor” mule.[488] Yet, notwithstanding these and other improvements, it can still be said that the fundamental motions of the mule remain the same as in Crompton’s original machine. [Footnote 488: It was not until the last quarter of the nineteenth century that the self-actor mule entirely displaced the hand-mule (Chapman, _ibid._, pp. 69-70).] For a time in the early part of the nineteenth century the mule came into use to such an extent that it appeared that it would entirely displace the water-frame. With the appearance of the “Throstle,” which was really an important improvement in the water-frame, the tendency was somewhat checked, and later in the century with other improvements the supremacy of the mule was again challenged. Consequently the great rival of the mule at the present day in the world’s cotton industry is the “Ring Spinning Frame,” which may be regarded as standing in much the same relation to the original water-frame, as does the self-actor mule to the original mule. The following figures show the position in recent years:-- COTTON-SPINNING SPINDLES. SPINNERS’ RETURNS, 31ST AUGUST IN EACH YEAR[489]