POPULAR ASTRONOMY. 



251 



nights which furnish the observations 

 are close together the three positions 

 would lie almost in a straight line and 

 the calculated curve would have no 

 high degree of accuracy. If the obser- 

 vations are separated more and more 

 the resulting orbit comes out more ac- 

 curately. Amassing all the observa- 

 tions of the comet at its last appear- 

 ance in 1835, the astronomers have 

 been able to trace its path out into the 



of these "perturbations," as they are 

 called, were quite simple, for the 1835 

 return, but very difficult for the pres- 

 ent appearance, due to the near ap- 

 proach to Jupiter, and the result is that 

 the many published orbits differ quite 

 considerably. The two that most 

 closely represent the comet's path are 

 one by Cowell and Crommelin, of the 

 Greenwich observatory, the other by 

 Dr. J. Floletschek, of France, each of 



Dec. MOON PHASES 

 LastQ'tr..Dec.4. 

 New Moon Dec.I2. 

 First Q.'tr.,Dex. 19. 

 Full Moon TJec.26. 



Evening SkyM ap for December 



vBy Jrof. 



urn f * 



Column 

 Univers^ 



FACE SOUTH' AND 

 HOLD THE MAP OVER 

 YOUR HEAD-THE TOP 

 NORTH. AND YOU WILL SEE 

 THE STARS ANDPLANETS 

 JUST AS THEY APPEAR 

 INTHE HEAVENS. 



S0U T H 



■POSITION OF VENUS 

 IN EABLY 'WESTERN) EveN ; 

 ING SKY IN DECEMBER. 



depth of space beyond the outermost 

 planet of the solar system, Neptune. 



If the sun and the comet were the 

 only bodies in the solar system, the 

 comet would travel around the sun in 

 a perfect ellipse, but Jupiter, Saturn 

 and the other planets all exert their 

 influences and pull the comet out of 

 its ellipse with forces depending on 

 the masses of the planets and its dis- 

 tances from them. The calculations 



them giving the time of passage about 

 the sun within three days. 



The Rev. Father George M. Searle, 

 Supervisor General of the Paulist 

 Fathers of New York City, has calcu- 

 lated from the English orbit that on 

 the night of May 18 the comet will 

 come nearest the earth, when it will 

 be 14,000,000 miles away. The comet 

 will probably travel across the face of 

 the sun, but there is no danger of the 



