6 



Waiter Gyllenberg 



mentioned ruade at Greenwich, and besides observations made by Huggins and 



Seabroke. The results obtained by Homann from these observations were tbe 

 following: 



Observations Apex Sun's relative velocity 

 a 8 



Greenwich 320°.l + 41°.2 39.3 ± 4.2 km, 



Huggin's 309°. 5 + 69°.7 48.5 4 23.1 » , 



Seabboke's 278 u .8 4- 13°.6 24.5+ 15.8 » . 



Mr. Homann was very well satisfied with these elements, and the values obtained 

 from the latter two series, seem to him in spite of the small number of stars 

 entered to agree very well with the results from the Greenwich observations. He says 

 also in the report of his paper, that in spite of the large difference in the results, 

 a certain agreement may be observed, and especially concerning the relative velocity 

 of the sun we may infer that this can scarcely diverge to a any considerable extent 

 from 30 km per sec. 



2 In 1888 the first systematic attempts to measure the displacements of the 

 spectral lines with aid of photographic methods were made by H. C. Vogel. In this way 

 it was possible to get a considerably greater exactness of the results. In the course of 

 the next four years he measures the spectra of 51 of the brightest stars 1 and assumes 

 that the mean error in every measurement does not come up to 2.0 km per sec. 

 That the number of stars was so small was exclusively due to the instrument used. 



From these observations Kempp 2 and Risteen 3 tried to determine the velocity 

 of the sun and the solar apex. The following results were obtained by Kempp: 



p ... , a= 206°.i i 12°.o, 



Position ot the apex 



F 8 = 4 45°.2 4 9°,2, 



Sun's relative velocity £=18.6 + 2.9 km per sec. 



In his solution, each star was entered with an individual weight. Another 

 solution, where all stars were assumed to have the same weight, gave no principal 

 deviation from the above results. It seemed, howewer, to him very important to make 

 a new solution where neighbouring stars, obviously belonging to the same cluster, 

 were rejected, all except one. The number of stars in this way diminished to 41 led 

 to the following solution: 



„ . . . L , a= 159°.7 + 20°.2, 



Position ol the apex 



§ = 4- 50°.2 ± 14°.s, 

 Sun's relative velocity #=13.0 + 3.3 km per sec. 



1 Publ. des Astrophysikalischen Observatoriums zu Potsdam. VII: 1. 1892. 



2 Versuch einer Ableitung der Bewegung des Sonnensystems aus den Potsdamer Spectro- 

 graphischen Beobachtungen von H. C. Vogel. Astr. Nachr. 132. 81. 1893. 



3 The sun's motion through space, by A. D. Risteek. The Astronom. Journal. 13. 75. 1893. 



