Note 4 — Chapter I
Reading edition
Out of eighty stars compared, fifty-seven were found to have changed their places by more than 10″. Lesser discrepancies were at that time regarded as falling within the limits of observational error. Tobiæ Mayeri Op. Inedita, t. i., pp. 80, 81, and Herschel in Phil. Trans., vol. lxxiii., pp. 275-278.