ABOUT COMETS. 



793 



It seemed very desirable that elliptic elements should be deter- 

 mined for this comet without making any previous assumptions in 

 reference to any of the elements ; this was undertaken independently 

 by two astronomers of the United States Naval Observatory, each 

 from different data. Professor Frisby made use of observations of 

 October 25th, November 7th, and November 20th. Mr. Upton selected 

 the following dates : October 25th, November 23d, and December 22d. 



The results of these two computations agree very closely : the re- 

 sulting period is only a few days less than six years. The inclination 

 of the plane of the orbit to the plane of the ecliptic is about five and 

 one half degrees. 



To show more strikingly the remarkable situation of the comet's 

 orbit with reference to the earth's orbit, the attention of the reader is 

 directed to the accompanying diagram (Fig. 1), which, for the sake of 



Fig. 1. 



OcT.10.1830. 



Nov,8. 



I3SI. 



simplicity, shows the two orbits as if in one plane, when in reality the 

 angle of inclination between them is about five and one half degrees. 

 The line marked '^ line of nodes " is the line of their mutual intersec- 

 tion, the part of the comet's orbit in the vicinity of the perihelion 

 being north of the plane of the ecliptic. 



The relative situations of the earth and comet are shown by their 

 positions in orbit at the date of discovery of the comet, October 10 ; 

 the date of the perihelion passage, November 8, 1880, and January 1, 

 1881. 



