Finally, the improvements in the operative machines have, while reducing their size, increased their speed and efficiency, as in the modern power loom; or, while increasing the size of their framework, have also increased the extent and number of their working parts, as in spinning mules, or have added to the speed of these working parts by imperceptible alterations of detail, such as those which ten years ago increased the speed of the spindles in self acting mules by one fifth.