A two-page 1875 article from the journal Engineering describing differential gear mechanisms on self-acting spinning mules built by Jacob Rieter and Co. of Winterthur. It covers a 468-spindle self-actor with a differential motion on the spindle drum shaft, and a 504-spindle self-actor for fine yarns built on the Parr-Curtis system. The text explains the drums, cones, levers and catches, and gives a gear-ratio calculation, with two cross-section drawings.