78 KNUT LUNDMARK, GLOBULAR CLUSTERS AND SPIRAL NEBULJS. 



tion in the great star-cloud in Cygnus. On plates taken with the Upsala 6-inch 

 twin telescope the number of stars within each magnitude has been determined for 

 stars between the 9th and 15th magnitude. Nearly 500 000 stars are thus classified 

 and provisional results have been derived. A preliminary determination of the 

 parallax of the cloud by using the results of the star-counts and the formula (3) 

 gives the following value: 



St = 0", 0001 5. 



Pannekoek in M. N. 79: öoo, 1919 has found a considerably smaller value, viz. 



7C == 0", 000025. 



Most classes of objects that must be considered as related to the galactic 

 clouds cannot be regarded as being at greater distances than 1000 — 10000 light-years. 

 This especially is the case with the novse and O-stars. 



By use of the same methods as those employed for the globular clusters, I 

 have studied the distribution in space of the open clusters, which evidently form a 

 skeleton of the Milky Way. The distances thus found give an average of 15 000 

 light-years. 



Several other facts are also indicating that the distance to the galactic clouds 

 cannot be regarded to be as great as is demanded by assuming the globular clusters 

 as being related to the Milky Way. To be sure, a considerable number of globular 

 clusters appear to be intimately connected with the Sagittarius-cloud, but never- 

 theless it seems not at all plausible that the extent of the Milky Way should be as 

 great in other directions, and it appears questionable whether already 100 000 light- 

 years is not too great a value for its diameter. 



Upsala, Astronomical Observatory, Jan. 26th, 1920. 



Tryckt den 5 februari 1920. 



Uppsala 1920. Almqvist & Wiksells Boktryckeri-A. -B. 



