THE MINOR PLANET MT 1911. 219 



and difficult problems of planetary motion. Then there are the 

 classes of very great excentricity or of great inclination, which 

 give rise to other problems, and so on. The only other groups 

 at present known are the Jupiter 6o° group and Eros, but Pro- 

 fessor F. W. Brown considers that there may be Jupiter i2.y 2 ° 

 planets, and, if instruments were powerful enough, astronomers 

 might find a Saturn group of planets. 



It is very desirable that the minor planets should be observed 

 at every opposition, but this would be impossible without 

 organized effort, ami that is now being made. At, I believe, the 

 initiative of Dr. F. Cohh, of the Berliner Jahrbuch, the sky is 

 divided into four zones, three of which are allotted to northern 

 observatories (Heidelberg, Dr. Wolf ; Taunton, Rev. J. Metcalf; 

 and Simeis, Crimea. Herr Beljawsky), whilst the southern zone, 

 from — 9 southwards, is allotted to the Union Observatory. Very 

 precise positions of the minor planets, except in rare cases, will 

 not be required ; from the ordinary observations the orbits of the 

 large number of minor planets will be corrected empirically from 

 time to time, and in this way it is hoped that knowledge of the 

 group will be gradually perfected and that unusual objects may 

 be the more readily picked out. 



When referring to the discovery of Eros it was mentioned 

 that this did not fall to one of the veterans, of whom Herr Palisa 

 is to-day the chief ; but recently he has had his compensation. I 

 do not mean that the astronomical world has overlooked his 

 whole-hearted devotion to this branch of astronomy, his precise 

 and long-continued visual observations and his numerous dis- 

 coveries, or that the valuable YVolf-Palisa star-charts are not 

 appreciated. I mean that it is a compensation when long-con- 

 tinued and faithful work is rewarded by a rare discovery. Herr 

 Palisa's discovery of 191 1 MT and its subsequent story has some 

 resemblance to the discovery of Ceres by Piazzi. Palisa dis- 

 covered this object on the night of October 3, 191 1, and he 

 observed it again on the following night. Its unusual motion at 

 once arrested his attention, and he telegraphed for further obser- 

 vations to all likely stations. Instead of the object's Right 

 Ascension decreasing whilst in opposition, it was increasing, 

 which at once stamped it as extraordinary. Fortunately, as a 

 result of Palisa's message. Pechule. of Copenhagen, managed to 

 measure the object's position on the night of October 4. After 

 that date clouds and moonlight interfered to such an extent that 

 the object was not seen again. Palisa had faith in his observa- 

 tions, and cabled to us to photograph the region, and Mr. Wood 

 did so on the nights of October 13, 14, 16. 18 and November 15, 

 but we also suffered from the atmosphere, and the onlv excellent 

 plate was that of October 18. It was duly searched, and a new 

 planet found, which was suspected to be MT. but it was a different 

 one. and is at present known as 191 1 MU. The remarkable part 

 of the business comes now ; the methods devised by Gauss for the 

 computation of an orbit from observations require that the dates 

 of observation in the case of a minor planet should be spread 



