stellar clusters 



53 



Description of the plates. 



Plate I, ßfi. la illustrates the relation between the galactic squares and the 

 constellations. Only the principal constellation is generally given for each square. 

 The dotted line indicates the course of the celestial equator. The big stars show 

 the position of the poles. 



Plate I, fig. I h gives the apparent distribution of the ordinary chisters in 

 Table 1. 



Plate II gives the distribution of the clusters in the galactic plane (= XY- 

 plane). The positive Xaxis is directed against the auti centre (Cygnus). The line 

 of intersection between the galactic plane and the celestial equator is indicated on 

 the diagram. The angle between the ascending node [il] of the galactic plane on 

 the equator and the positive X-axis is 55". 



The origin of the system of coordinates coincides with the sun. The squares 

 of the coordinate-net have a side having the length of 100 siriometers. AU the 

 clusters registered are thus within a distance of 300 siriometers from the sun. 



Plate III, fig. Ill a gives the coordinates of the clusters in the XZ-plane. 

 Tiie position of the centre of the system of clusters in the direction of the negative 

 X-axis is here better shown than on plate II. The great dispersion in .^-coordinates 

 for clusters having an //-coordinate between + 100 and -|- 200 siriometers is striking. 



Plate IV, fig. IV a gives the apparent galactic distribution of tlie globular 

 clusters. Unlike plate I the ascending node of the galactic plane on the equator 

 is lure placed in the midst of the diagram, as may be concluded from the path 

 of the celestial equator as well as from the designations of the galactic squares. 



Plate IV, fig. IV h gives the apparent galactic distribution of the planetary 

 nebulae. All nebulae denoted in Dreyers catalogues as planetaries, or suspected 

 planetaries, are here considered, excepting those in the Magellanic clouds and in 

 Coma Berenices. The number of these are 32. The number of remaining planetaries, 

 registered in the diagram, is 100. 



The projection is the same as in fig. IV a. The similarity in the distribution 

 of these two kinds of objects is obvious. Even the effect of the dark nebula in 

 Sagittarius is here indicated even stronger than regarding the globulars. 



Plate V gives the distribution of the globulars in the galactic plane. The sun 

 is in the origin, the X-axis is as usual directed against the anti-centre. The glo- 

 bulars are almost exclusively to be found in the direction of the negative F-axis 

 [Sagittarius). The squares of the coordinate-net have a side of 10 siriometers. The 

 greatest distance of the globulars amounts to 80 sirioraeters. 



