416 SCIENTIFIC RECORD FOR 1885. 



The values of the mass of Neptune from Hall's measures at different 

 oppositions, and from those of Lassell and Marth and of Holden, differ 

 sensibly. The mean result from Hall's own observations is ygi^-^ ; he 

 remarks that his distances are generally smaller than those of other 

 observers, and believes that in order to eliminate the effect of such pei;- 

 sonal equation from the determination of the mass of a planet, the only 

 way will be to increase the number of observers and to take a mean of 

 the results. On favorable nights examinations of the region about 

 Nepturfie were made, but no other satellite was detected. 



Photometric observations of Neptune. — A series of observations of the 

 planet's magnitude was carried on with the meridian photometer at 

 Harvard College Observatory from December 16, 1884, to January 21, 

 1885 ; the resulting magnitude for mean opposition is 7*63. Professor 

 Pickering regards it as improbable that there is any variation in the 

 light of Neptune of a strictly periodic character. 



The Trans-Neptunian Planet. — In the twentieth volume of the 

 American Journal of Science, page 225 et seq., Prof. D. P. Todd, now of 

 Amherst College, gave an account of his search, theoretical and ])r9;C- 

 tical, for the trans-Neptunian planet, made from November, 1877, to 

 March, 1878, with the 26-iuch refractor of the Washington Observatory. 

 Professor Todd has now published* the full details of his telescopic 

 work, giving a list of all "suspected objects," and transcribing his note- 

 book entire. 



It was expected that the planet would readily be recognized by the 

 contrast of its disc and light with the appearance of an average star 

 of about the thirteenth magnitude, and only approximate positions of 

 "suspected objects" are given, — generally by means of diagrams repre- 

 senting the configuration of stars seen in the large telescope and in the 

 field of the 5-inch finder. It would lighten considerably the labors of 

 any one who may go over this ground iu the future, if Professor Todd 

 had summarized his observations in some way, by establishing the 

 identity or non-identity of nebulous objects which he has noted, as 

 probably to be found in Herschel's General Catalogue, and by giving a 

 list of such objects as he was still, at the end of his work, inclined to 

 look upon with some suspicion. 



Although this search was unsuccessful, Professor Todd regards the 

 evidence of the existence of ^^the trans-Neptune planet" as well founded, 

 and he expresses the hope that the search may be continued with the 

 improved methods of astronomical photography. 



The Minor Planets. — During the year 1885 the number of minor 

 planets has been increased by nine, bringing the whole number now 

 known up to 253. The discoveries of 1885 were as follows : 



J'roc. 4m. Acad., 1885, 21 : p. 228-43. Aslron. ^'achr., 113 : 153-66. 



