2l8 THE MINOR PLANET MT I C> I I . 



ultimately realized, of getting images of the very faint eighth 

 satellite of Jupiter. The plates are of large size, being 16 inches 

 square, and cover about 325 square degrees of the sky, the scale 

 being precisely that of Argelander and Schonfeld's maps of the 

 Bonn Durchmusterung. The plates are exposed in the Franklin- 

 Adams 10-inch diameter, 44.6 inches focus, Star-Camera. On 

 examining the first plate he- got, Mr. Wood at once noticed 

 numerous trails of minor planets, no less than 15 in all, of which 

 five were new — this being the largest single haul yet accomplished. 

 When this was known in Europe, it was soon recognized that at 

 last an observatory in the Southern Hemisphere was in a position 

 to aid not only in the discovery, but in the equally, or perhaps 

 more, important work of following up and identifying planets at 

 oppositions which would be invisible to astronomers of the 

 Northern Hemisphere. Thus we were requested by cablegram 

 to obtain positions of the Jupiter-group planet 624 Hector in 

 191 1. It was then in South Declination 43 degrees and below 

 the 13th magnitude. At the same time a similar message was 

 sent to the Royal Observatory at the Cape. Hector was accord- 

 ingly photographed at both observatories, but the way in which 

 the one observatory helped the other is somewhat remarkable; in 

 the Astronomische Nachrickten for . September 5, 191 1, Mr. 

 Hough tells us how plates were taken with the Astrographic 

 telescope on July 4 and subsequent dates with a view to searching 

 for the planet, and although a preliminary search failed to reveal 

 the planet, it was found on these plates after the corrected position 

 had been notified from Johannesburg. Although we very cer- 

 tainly photograph any object anywhere near its predicted position, 

 our positions are not very exact because of the small scale of 

 the photographs, but they are more than sufficiently exact to 

 indicate the precise place to other observatories with superior 

 equipment in this line. In the case of such an interesting planet, 

 the Cape observations have already been utilized in the prepara- 

 tion of the ephemeris for the next opposition, and it is on the 

 list for re-observation in a few weeks' time.* 



One may say that now the lookout is for minor planets of 

 the rarer classes, and that the great desideratum is to be able to 

 discriminate readily betwixt the commonplace and the rare. The 

 great group of minor planets circling between Mars and Jupiter is 

 capable of much sub-division. There are, first, the four oldest- 

 known, which are much the largest, Ceres, Pallas, Juno and Vesta; 

 these and some others will be observed at many observatories 

 with every precision and their theories worked out with every 

 care. Secondly, there are the planets whose periods are near 

 to a sub-multiple of the period of the massive Jupiter, of which 

 Hecuba, whose period is closely but not exactly half that of 

 Jupiter, may be especially cited ; this species gives rise to refined 



* Hector was duly observed here on the 6th and 10th of August, 

 almost exactly in its predicted place. The observations were published in 

 the Astronomische Nachrichten, No. 4602, and appear to be the only ones 

 obtained at the last opposition. 



