2\C) THE MINOR PLANET MT I9TI. 



had been found, and not only found, but also so well followed 

 up that, generally speaking, their orbits were well known ; but a 

 few had been "lost." In 1891 Max Wolf, of Heidelberg, dis- 

 covered No. 323, Brucia, and, as was remarked at the time, it 

 was interesting as being the first new asteroid discovered by 

 photography. 



In Newcomb's Popular Astronomy (edition 1882) he 

 remarks : — 



" It will be seen that the rate of discovery has been pretty steadily- 

 increasing during thirty years. This is not because the number of those 

 visible, but not yet found, is so great that it is as easy as ever to find 

 one, but because they are now sought after with more skill and system 

 than formerly. . . . Professor Peters, in searching for these bodies, 

 falls upon several already known for every new one that he finds. Con- 

 sequently, were they all lost, he alone could re-discover them at a more 

 rapid rate than they actually have been discovered by the efforts of all 

 the observers engaged in the search. . . . The number of these bodies 

 now known is so great that the mere labour of keeping run of their 

 motions, so that they should not be lost, is out of proportion to the value 

 of its results. It is mainly through the assiduity of German students that 

 most of them are kept from being lost. Should many more be found, it 

 may be necessary to adopt the suggestion of a German astronomer, and 

 let such of them as seem unimportant go again and pursue their orbit 

 undisturbed by telescope or computer." 



Newcomb's remarks were made nine years before Max 

 Wolf's first discovery, and. as far as I know, he never referred 

 to the subject again. In 1893 it was announced that no minor 

 planet would be given a permanent number until five observations 

 were available, but to-day a permanent number is not given until 

 observations spread over six weeks are available and a satisfac- 

 tory orbit is computed. In 1S93 the provisional designation by 

 the year and a letter, which is still in force, was adopted, so 

 that the record of discoveries in that year started with 1893 A 

 and finished with 1893 AP. And so matters went on until [89S, 

 by which time the lettering had got to ED and the permanent 

 numbers to 436; but one discovery, in 1898. produced a great 

 sensation, the discovery by Witt, at Berlin, of the minor planet 

 Eros, whose mean distance is less than that of Mars and which 

 can approach the Earth with 0.149 of the mean distance of the 

 Sun. The value of this planet for finding the parallax of the 

 Sun was at once seen, and although Eros will not make a very 

 close approach to the Earth until 193 1, it was determined to make 

 use of the fairly favourable opposition of 1900. Here it will 

 suffice to say that, on the 9th February, 1912, the Gold 

 Medal of the Royal Astronomical Society was awarded to Mr. 

 Arthur R. Hinks, of the Cambridge Observatory, for his '* De- 

 termination of the Solar Parallax from Observations of Eros." 

 It will be remembered that almost simultaneously with the dis- 

 covery of Eros, Sir David Gill published the result of his re- 

 searches, using observations of the minor planets, Victoria. Iris 

 and Sappho, made in 188S-1889. His value of the parallax was: 



8". 802 ± o".oo5 

 Mr. Hinks's is 8".8o6 + o".oo4 



