38 



The irregular progress of tlie quotients is partly to be ex- 



plained from our counting only a small part of the cluster. 



These numbers give the following values for the parallax: 



I ji = 0".0004 



II 4 



III 7 



IV 13 

 V 11 



VI 4 



Mean 



?r=:0".0007 dr 0''.0002 



From 142 cluster variables that are equally distributed over the 

 cluster and occur in Miss Le.witt's catalogue, we find for the mean 

 apparent magnitude of these stars ?« = 14.67 and 5 log. -t = — 15.77, 

 so that the mean absolute magnitude of these (f Cephei variable 

 stars with a short period is M = 'S.Q according to our delermination 

 of the parallax. 



From some (f Cephei variable stars with a long period Hertzsprung 

 found for the parallax of the Small Magellanic Cloud nr = 0".0001. 



Pr'aesepe. 



«,„, = 8^34"' 39% rf,,„„ = + 20°r, è = + 33°, /=169°. 



Dr. P. J. VAN Rhijn. The proper motions of the stars in and near 

 the Praesepe cluster, Publ. Groningen, N'. 26, 1916. 



The measurement of 2 sets of plates, taken at Potsdam. The 

 catalogue contains 531 stars. The diameters were reduced to photo- 

 graphic magnitudes by means of standard magnitudes, determined 

 by Hertzsprung. The probable error of a magnitude is ± 0'".12. 



We have derived the visual magnitudes from the photographic 

 ones in the same way as Van Rhijn did on page 10 of his publi- 

 cation. The correction was determined from the value of the colour 



