KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 60. NtO 8. 5 



A necessary condition for obtaining good values for tu by means of this method 

 is, that m is fixed in an absolute photometrical scale. The extensive work that has 

 been performed at the Harvard and Mount-Wilson Observatories for tbe fixing of a 

 photometric scale round the pole, has a great importance for researches of this 

 kind. For the står magnitudes here in question these sequences can certainly be 

 regarded as representing a scale, that may very nearly be considered as the exact one. 



Finally, by using the 28 globular dusters for which the parallax has been 

 thus obtained from variable stars and from magnitudes for the brightest stars, 

 Shapley determines the connection between the apparent diameter and the parallax; 

 and he then obtains, by means of this connection, the parallaxes for the remaining 

 41 globular dusters through measures of the apparent diameter, performed by him 

 and Miss Helen Davis. 



Treating the question of the distances of the globular dusters, Charlier starts 

 from the presumption that the absolute dimensions of these objects vary within 

 rather narrow limits, and that the apparent diameter must consequently be a proper 

 measure of the distance. This supposition is justified by Shapley's statement in 

 his sixth paper. By using Bailey's values for the diameters of globular dusters, 

 Charlier thus obtains their relative parallaxes, and now there only remains the 

 determining of the scale- value for obtaining the absolute dimensions of the distances. 

 Determining this constant, Charlier supposes, on account of the concentration of 

 the globular dusters in the står cloud in Sagittarius and of their strongly symmetri- 

 cal distribution in relation to the galactic plane, that they are to be regarded as 

 related to the Galaxy. This supposition he regards as having a strong support in 

 the fact that the apparent distribution of the planetary nebulae is accordant with 

 that of the globular dusters. Regarding the correctness of this statement one may 

 perhaps be in doubt, on account of the fact that in the står cloud in Sagittarius 

 the concentration of planetary nebulae is not so pronounced as that of globular 

 dusters, and, besides, in that hemisphere of the sky, where only 15 % of alt the 

 globular dusters are to be found, there are no less than 40 % of all the planetary 

 nebulae. Furthermore, Wolf, in his Catalogues of Nebulae, classifies rather a great 

 number of nebulse as planetary ones (in Wolj^s Nebelliste No. 3 thus occur 30, in 

 No. 5 24 planetary ones). On the contrary, he seems not to ha ve found one single 

 globular duster in the same regions, a fact which shows that the planetary nebuloe 

 concentrate also in regions where globular dusters occur only separate or not at all, 

 and that, accordingly, no great concordance, except the mutual concentration in the 

 står cloud in Sagittarius, can with certainty be said to exist between the apparent 

 distribution of globular dusters and planetary nebulae. Yet, there seems to exist 

 some strong reasons for assuming that globular dusters are related to the Galaxy, 

 and, consequently, with the acceptance of Charlier's suppositions, the question of 

 the determination of their distances can be reduced to the question of the deter- 

 mination of the dimensions of the galactic system, by which, however, a rather great 

 amount of uncertainty is brought in, as the question of the dimensions of the Milky 

 Way can scarcely be regarded as satisfactorily solved as yet. 



