24 KNUT LUNDMARK, GL0BULAR CLUSTERS AND SPIRAL NEBULiE. 



It would be of great interest to see whether the velocity V increases when 

 faint stars are involved in the determination of Apex. On my request, Mr. K. Litt- 

 marck has determined the solar Apex from those stars with considerable radial veloci- 

 ties and small proper motions, compiled by Perrine in A. J. 30 153 . 



He finds from the 71 equations of condition, assuming K = 0, the following 

 normal equations: 



+ 16,119 X + 2,527 Y + 2,957 Z =' + 0,899 

 + 2,527 +12.639 + 1,954 = — 1,827 

 + 2,957 + 1,954 +29,194 =—5,071 



From this he obtains: 



^=310°,6 £>=+50°,o 



F = -27,7 kra /sec. 



Between the Apex calculated from the radial motions of globular clusters and 

 the one found by Wirtz 230 from the motions of spiral nebulse, there is also a remark- 

 able concordance prevailing. The directions of the solar motion coincides closely. 

 The speed of the sun's motion is, it is true, double the size in the latter case than in 

 the former, but, nevertheless, of the same order of magnitude. In Table IV 1 I have 

 compiled all material that has been at my disposal regarding the radial velocities 

 of the spiral nebulse. We find, that the velocities have been determined with 

 tolerably great certainty, regard having been taken to their considerable magnitude. 

 Besides for 18 spirals the radial motions are also determined for the great and the 

 small Magellanic clouds. The remarkable concordance I have found between the 

 structure of the great Magellanic cloud and the nebula 4449, classified as a spiral 

 one (Hikks, Wolf), and with a spectrum typical of the spiral nebulse, causes, that 

 we must in reality, perhaps, consider the Magellanic clouds as the nearest spiral 

 nebula?, Pl. 1. This circumstance may perhaps justify my employing these objects 

 at our Apex-determinations. Owing to the fact that recent spectrographic researches 

 have shown that it is difficult to draw a definitive limit between planetaries and 

 spirals, because the latter often show also the spectrum typical of the proper nebulse, 

 and planetary nebulse sometimes show spiral structure 170 (N. G. C. 1514), I have 

 considered it appropriate to employ the four planetaries, possessing radial velocities 

 comparable in size with those of spirals. The predominance of positive radial velo- 

 cities shows the justifiableness of taking in the constant K in the equations of con- 

 dition, but the latter have also been solved with the hypothesis K = 0. 



According to the equation (10) we öbtain the following 24 equations of con- 

 dition for the radial velocities included in the Table IV. 



1 Wolf has determined a number of radial velocities for spiral nebulse, but only stated the direction of 

 the motions, not their size. He finds thus: 



N. G. C. 224 — N. G. C. 3031 + 



598— 4194 + 



6853— 4826 + 



