

NEBULA, CLUSTERS, ETC. 31 



Herschel, W. : Abstracts of Memoirs — Continued. 



A.D. Vol. P. 



in which case the nebulosity must soon assume the form 

 of the cluster, and will finally be absorbed by it. 

 Class 3. Twenty-six easily resolvable objects. 

 1814 104 262 Class 4. Twelve objects, probably clusters. 

 IX. Of the siderial j)art of the Heavens. 

 Intimate connection between the nebulous and siderial 

 condition. 



263 Stars of first magnitude. [See P. T., 1785, p. 68.] 



264 Prismatic analysis of the light of Sirius, a Orionis, Procy< n, 



Arcturus. Aldebaran and a Lyras* 



265 X. Of the aggregation of stars. 



Star-gauges prove that the stars are not equally distributed 

 over the celestial regions. 



Forming clusters. This tendency to clustering is chiefly 

 visible in places extremely rich in stars. Its greatest 

 effects will then be in and near the milky way. 



266 The twenty objects referred to are not given as instances 



of the actual formation of clusters, but merely to draw 

 attention to a seemingly aggregating arrangement. 

 Fifteen of these are in the milky way and five are near 

 it. 



266 XI. Of irregular dusters. 



Clusters in very rich parts of the heavens are generally of 

 irregular form and imperfectly collected. One hundred 

 $267 and twelve such objects are referred to ; eighty of size 

 not noted, fifty-three of these in the milky way, eighteen 

 near it, nine at a distance from it. Also thirty-two ir- 

 regular clusters from 2' to 30' in diameter ; of these 

 twenty-two are in the milky way and ten near it. 



267 The great number of clusters in these two collections is not 



only an indication that they owe their origin to a clus- 

 tering power residing in the centre; but the still re- 

 maining irregularity of their arrangement additionally 

 proves that the action of the clustering power has not 

 been exerted long enough to produce a more artificial 

 construction. 



268 XII. Of clusters variously extended and compressed. 

 Fifteen extended clusters named ; twelve in the milky way, 



three near it. Their descriptions show that the power 

 which has drawn the stars together has acted under dif- 

 ferent circumstances in the several cases. 



[*I believe that these experiments of Herschel's have been hithertoover- 

 looked, at least I have seen no mention of them in historical works. 



