PROGRESS OF ASTRONOMY FOR 1891 AND 1892. 



687 



dred sets of measures of each of the ten stars — that number being 

 required in his opinion to furnish paralhixes with probable errors not 

 much above 0".01: 



o Tauri 



a Auriga," 



a Orionis 



a Cania Minoris 

 /3 Geminoruni. . . 



a Leoni.^i 



a Bootis 



a LjTffi 



a Aqmto 



a Cygni 



. Determination of stellar parallax tcith a transit instrument. — Prof. 

 Kapteyn has published a paper of much interest, upon the determina- 

 tion of relative stellar parallax by observations of the differences of 

 right ascension between the selected star and neighboring comparison 

 stars made with the transit instrument and chronograph. The compar- 

 ison stars are selected of about the same declination as the star whose 

 parallax is to be determined and symmetrically situated at slightly 

 greater and less declinations. The differences of right ascension and 

 of magnitude should be small. Special precautions are taken to elimi- 

 nate all ordinary instrumental errors, particularly the error of clock 

 rate, which has an important effect. 



The following are the results published by Prof. Kapteyn. The prob- 

 able error given in each case is not far from i0."03: 



Parallax of <J Herciilis. — Prof. Leavenworth has found a parallax of 

 -|-0."05() i()."014 from his own observations of this star; and from a 

 series of observations published by Dembowski in his '' Double Star 

 Observations," -f-0."030 dL0."015. 



Parallax of P Ursce Majoris. — Dr. Franz finds from heliometer ob- 

 servations of this star at Konigsberg from 1883 to 1800 a parallax of 



