This disposition of the parts is even now to be found in most Twiner Mules, that is, mules used to double two or more single threads together without any process of drawing being applied to the cotton.
When Crompton applied the principle of drawing rollers, his ingenious mind saw that it would be best to let the rollers, roller beam, and roving creel be in a fixed framework on account of their combined weight and size, making it very difficult to move them about.
Crompton's great idea seems to have been to produce a better thread by his machine than could be given by other machines, and in this he admirably succeeded.
The mule being set in motion, the rollers first attenuated and then delivered the cotton to the spindle carriage. The latter, by the action of the hand and knee, was made to recede from the rollers just about as fast as the cotton was delivered to the spindles, or possibly at a rather quicker rate. Then, while the thread was still in a soft state, the rollers could be stopped and the threads pulled still finer by the continued recession of the spindle carriage from the rollers. Afterwards, when that length of thread was fully made, it wound on the spindles, and the carriage at the same time returned to the roller beam.
Thus each portion of thread was first subjected to the action of drawing rollers, as in Arkwright's machine, and then drawn still finer by the withdrawal of the travelling carriage, as in Hargreaves' Jenny.
Shortly after Crompton's invention was given to the public, it began to be improved in various ways. Henry Stones, a mechanic of Horwich, near Bolton, substituted metal drawing rollers for Crompton's crude wooden rollers, doubtless copying the idea from Arkwright's water frame.
All the mules employed at first were necessarily short; by that is meant they contained but few spindles, often 40 or 50 spindles. The biggest mule in Bolton in 1786 was said to contain 100 spindles. The preparation of the rovings for the mule about this time occupied the attention of Crompton, and he invented a Carding Engine which, however, did not attain very much success. Indeed it is said that one day so incensed was Crompton at the way he had been treated on account of his mule, that he took an axe and smashed his engine to pieces.