NEBULAE, CLUSTERS, ETC. 25 



Herschel, W. : Abstracts of Memoirs — Continued. 



A.D. Vol. P. 



1802 92 487-495 Hypothetical examples of such connections. 



495 IV. Of Clustering Stars and the Milky Way. 



Marks of clustering in the milky way. Example of the 

 stars between /3 and £ Cygni. 



496 " We may indeed partly ascribe the increase, both of 



brightness and of apparent compression, to a greater 

 depth of the space which contains these stars ; but this 

 will equally tend to show their clustering condition, for 

 since the increase of brightness is gradual, the space con- 

 taining the clustering stars must tend to a spherical 

 form if the gradual increase of brightness is to be ex- 

 plained by the situation of the stars." 

 V. Of groups of Stars. Definition. 



497 VI. Of clusters of Stars. Definition. 



VII. Of Nebulce. Perhaps they are all to be resolved into 

 the three last-mentioned species. 



498 Power of a telescope to penetrate not only space but time 

 [past.] 



499 VIII. Of Stars with Burs or Stellar Nebulae. 

 IX. Of Milky Nebulosity. 



Probably of two kinds. 1st, apparent, which is formed by 

 distant ["widely-extended"] clustering stars, and, 2d, 

 real, and possibly at no very great distance from us. The 

 nebula of Orion of this latter kind. 



500 X. Of Nebulous Stars. 



501 XI. Of Planetary Nebulce. 



Perhaps they are allied to nebulous stars. 



XII. Of Planetary Nebulce with Centrzs. 



603 Catalog 



1811 101 269 Astronomical Observations relating to the Construction of 

 the Heavens, arranged for the purpose of a critical ex- 

 amination, the result of which appears to throw some 

 new light on the Organization of the Celestial bodies. 



[The following analysis is by Hersciiel himself.] 

 50 



