Animal Address to the Members. Ivii 



'of love outside the routine of his office. Kapteyn had naturally 

 found many anomalies between the results of the Cape photographic 

 plates and those of previous Star Catalogues, of which he prepared 

 special lists, containing stars existing in other catalogues not found 

 on the Cape plates. 



Every one of these many hundred cases has been examined, and 

 in hardly a single instance has an error been found in the Cape 

 Durchmusterung — the discrepancies generally arise from misprints 

 or errors of reduction in the other catalogues, or the stars have 

 proved to be variable or so red as not to be photographically bright 

 enough to produce an imipression. A complete account of this 

 revision, together with numerous observations of variable stars, is now 

 in press. 



The more pressing duties of the Cape Observatory had prevented 

 the devotion of much of its time to the observations of double stars. 

 Maclear, it is true, had made a long series of observations of a 

 Centauri and of a few of the most interesting of the other double 

 stars then known ; Ellery at Melbourne had also made a number of 

 measures, but during the past twenty-five years the only Observatory 

 which had systematically devoted a considerable part of its time to 

 this object was that of Sydney, where, under Mr. Eussell's direction, 

 many valuable series of observations were made. 



Mr. Innes, previous to his arrival at the Cape, had devoted himself 

 to this branch of astronomy, and, with comparatively feeble means, 

 had discovered about forty previously unknown double stars and 

 published their estimated distances and position angles. In the 

 course of his revision of the Durchmusterung, and by making use of 

 opportunities of exceptional definition, he has now added about three 

 hundred to the list of known southern double stars, all of a class 

 that would appear single in our photographic plates. He has also 

 applied the 18-inch refractor of the new McClean telescope to that 

 work, and with Mr. Lunt has made many measures of the position 

 .angles and distances of southern double stars. In addition to this 

 he has prepared a reference catalogue of southern double stars with 

 a bibliography of the subject, which is published in the Annals of the 

 Cape Observatory, vol. ii. part 2. 



I have referred briefly to Henderson's discovery of the parallax of 

 Alpha Centauri ; let me endeavour now to place its importance 

 before you in its true light. If we observe the position of a fixed 

 star on dates six months apart we are virtually observing it from two 

 points of space 186 millions of miles apart, because in the course of 

 that time the earth occupies two opposite points in its orbit round 

 the sun, and the earth's distance from the sun is approximately 



