COMET OF 1889-1896-1903 219 



INTRODUCTION. 



1. This comet was discovered by William R. Brooks, at 

 Geneva, New York, July 6, 1889, and was observed until Janu- 

 ary, 1 891. It was a faint telescopic object, never visible to the 

 naked eye, and showing no striking physical characteristics ; but 

 of interest on account of the orbit it described and of the many 

 problems in astro-mechanics which have arisen in the attempt 

 to trace its past history. After a very few observations had 

 been made, it was recognized as a periodic comet, travelling 

 in an orbit of about seven years, and a very interesting mem- 

 ber of Jupiter's so-called family. Chandler' was the first to 

 investigate its history and show that its orbit had been 

 changed radically by a close approach to Jupiter in 1886; 

 that before that time the comet was moving in an entirely 

 different orbit from that in which it has since moved. The 

 interest in the problem was still further increased by the 

 statement of Chandler that the comet of 1889 was probably 

 identical with the lost comet of 1770 (Lexell). Chandler's 

 results, however, depended upon observations extending over a 

 period of three months only, and the perturbations during the 

 years 1886 to 1889 were neglected. In this paper Chandler 

 gave the period of the comet previous to 1886 as 26.9 years, 

 and upon the substantial correctness of these figures depended 

 his conclusions as to the identity with Lexell's comet. 



2. Lexell's comet was first seen by Messier on the night of 

 June 14-15, 1770. He at first thought it to be a part of the 

 nebula in the constellation Sagittarius but after a few nights he 

 recognized its cometary character. At this time it was faint and 

 invisible without the aid of a telescope, and appeared as a nebu- 

 losity about 5' 23'' in diameter. On June 21, however, it 

 became visible to the unaided eye, and three days later was as 

 bright as a second magnitude star. It was now seen to have an ill 



' " The Action of Jupiter in 1886 upon Comet d, 1889, and the Identity of the 

 latter with Lexell's Comet of 1770," Asfr. Joitr., 205, p. 100. 



