ADDENDA ET CORRIGENDA.
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26, line 27. Add:—"It was suggested by Bessel that some of the changes which he noticed to have been undergone by Halley's Comet in 1835-6 were the result of a rotation on its axis in a period of about 5 days, and a similar suggestion was made with respect to Morehouse's Comet of 1908 (iii). Both comets also suffered the loss, in a certain sense, of their tails for a time "
32. It is not quite certain to whom the pictures forming Plates VII. and VIII. should be ascribed, as some of the American photographs reached me without authors' names.
163, line 2. Add:—"Another term used in connection with the elliptic orbits of comets is 'the Epoch of Osculation', which is the time for which the perturbed orbit has been calculated. To get the time of perihelion passage from it take the Mean Anomaly, M (or 360°—M, if M is near 360°); reduce it to seconds and then divide it by the mean daily motion in seconds (μ); the quotient is the interval in days between the Epoch and the time of perihelion. Where M is an angle of a few degrees it means that perihelion precedes the Epoch, but where M is near 360° it means that perihelion follows the Epoch."
213, line 2. Add:—"But Pope in speaking of a 'Red Comet' when he describes Minerva's rapid descent from Heaven has tampered with the original Greek, for Homer says not a word about any comet, but evidently alludes to a falling star, or meteor of some kind." (Pope, Iliad, book iv, line 101; iv, 75, in the Greek.)
