A. MATHEMATICS AND ASTRONOMY. 23 



OEBIT OF THE BINARY STAR 70 (j9) OPHIUCHI. 



Since the first measure of position of this star by Sir 

 William Herschel in ITTQ, over two hundred separate ob- 

 servations have been made, which under ordinary circum- 

 stances would be sufficient to yield an accurate determination 

 of the orbit. Sir John Herschel, Bessel, Madler, and others 

 have successively determined orbits for this binary, in no 

 one of w^hich has a satisfactory agreement of theory with 

 observation been maintained over a considerable length of 

 time. Tisserand, of Toulouse (aided by Perrotin of the same 

 observatory), has given this orbit a thorough investigation, 

 and he finds that the conditions of the problem are such 

 that a partial indetermination exists in one of the elements. 

 Therefore he has solved the equations of condition involving 

 tlie elements, leaving one element undetermined ; and he 

 shows that, if the angles of position of this pair can be meas- 

 ured in 1885 so as to leave an error of not more than 0.2, 

 the doubtful element can be determined with at least five 

 times the exactness it now has. His complete w^ork will be 

 published in the 3Iemoirs of the Hoyal Academy of Tou- 

 louse for 1876. 6 J5, January 24, 1876. 



THE DOUBLE STAR BETA LEPORIS. 



This star is of the 3.5 magnitude, and was discovered to be 

 attended by a small (eleventh magnitude) companion by Mr. 

 S. W. Burnham, of Chicago, on December 14, 1874. On that 

 date Mr. Burnham estimated the distance of the companion 

 to be about 2 to 3 seconds of arc, the position-angle from two 

 measures being 269.1. Further measures have been made 

 by Dembowski, of Milan, and Hall, of Washington, as be- 

 low: 



1874, December 14.. S=2" to 3"; /j = 269.1 Burnham. 



1875.077 = .... ; =268.4 Dembowski. 



1875.112 = 2.89" ; =267.1 " 



1876.068 =2.71" ; =279.9 " 



1876, January 31.... = 3.16" ; =280.4 Hall. 



1876, February 17... = .... ; =283.6 " 



1876, February 18... =3.08" ; =279.0 " 



From these independent measures it appears that there has 

 been a change of position-angle of no less than 10 degrees 



