524 



[N. S. Vol. XLV. No. 1169 



E 

 Fig. 13 The (inner) Pleiades Nebula, photographed bj' Keeler with the Crossley Eeflector of the Lick 

 Observatory. (By engraver 's error the plate is reversed in one direction, as indicated by the letters 



W, N, E, S.) 



ing regions. The bright stars in the 

 Pleiades, those really belonging to the 

 cluster, are numerous, but within the clus- 

 ter as we see it, and in a considerable area 

 of the adjacent sky, the faint stars are 

 markedly scarcer than in the areas farther 

 away. Barnard has found that the sky in 

 the region around the Pleiades group is 

 possessed of much nebulosily. It is a nat- 



ural question, are the faint stars scarce be- 

 cause the nebulosity there existing has not 

 yet condensed into stellar forms? This 

 may be true in part, but we shall find much 

 more probable the view that the faint stars 

 are deficient in numbers because the nebular 

 materials, at a certain distance away from 

 us, are obstructing the light of the faint 

 stars that are farlher away from us than 



