14 KNUT LUNDMARK, GLOBULAR CLUSTERS AND SPIRAL NEBULiE. 



Finally, putting the frequency-curve for A —A 9 : 



" >8 2 g— 0802(^-3,4)2 



in (3), and solving the equation, we get: 



XM 3 =0". 000240, 

 7u Jtfi3=0" 5 000267. 



Thus we have obtained the following parallax-determinations for the two glo- 

 bular clusters: 



Tl m 3 



Weight 





~M 13 



Weight 



0",000043 



2 



0" 



.000106 



2 



210 



1 





190 



1 



240 



1 





267 



1 



290 



1 





154 



1 



0",000163 



0". 000 164 



from which we obtain: 



e' = 0,009. 



Besides for M 3 and 13 there are photometric data for Mil and 37. M 11 is 

 examined by Shapley, who has, by the same method as he has used regarding the 

 former star-groups, determined the colour-indices for 364 stars. In spite of the 

 high precision, which, no doubt, distinguishes Shapley's data also in this case, I 

 have not found it advisable to calculate e' from them, as M 11 seems through its 

 unmistakeable connection with the står cloud in Scutum Sobiesii to occupy a some- 

 what peculiar position among globular clusters. Shapley says, that the density of 

 the stars fainter than magnitudes 14,o or 14,5 is little, if any, greater in the cluster 

 than outside, and there is no evidence on any of the photographs of the existence 

 of the highly concentrated background of faint stars typical of truly globular clusters. 

 As a separating of the background cannot be done with the observations in hand, 

 I have not taken any consideration to the value for e' = 0,027, which follows from 

 the mean of the parallax 0",ooo4oo, which has come out of 4 determinations. 



For M 37 there exist measurements of photographic magnitudes, performed by 

 Nordlund, Giebeler and Joy, whereby the scales have been fixed by aid of von 

 Zeipel's visual magnitudes determined by means of a Zöllner photometer. As, 

 consequently, the magnitudes given by the first-mentioned authors can be regarded 

 neither as correct visual ones nor as photographic ones, I have not desired to delay 

 with the determination of the scale-value from this cluster, until the appearance of 

 Shapley's and von Zeipel's photometric catalogues över M 37, that are now being 

 worked out. 



