BIBLIOGRAPHY- OF IIERSCHEL's WRITINGS. G03 



Herschel, W.: SY^•OPSIS of the Writings of— Couf inued. 



A..D. Tol. P. . ^, 



1814 104 261 Class 2. Twenty-six objects of rouiul or nearly round fignre. Ihe 

 round figure of these show them to be (jlobular. They must cither 

 he in a condensed state purely nebulous, or else, if consisting of 

 stars, they mi^st he in an advanced order of compression, and only 

 appear nebulous on account of their very great distance from us. 

 A middle state between the progressive condensation of a globular 

 nebula and a cluster of stars can have no existence, because a glob- 

 ular nebulosity when condensed can only produce a single star. A 

 globular cluster may, however, intercept a mass of nebulous matter 

 ki motion, in which case the nebulosity must soon assume the form 

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

 Class 3. Twenty-sis easily resolvable objects. 



262 Class 4. Twelve objects, probably clusters. 

 IX. Of the sidereal imrt of the Heavens. 



Intimate connection between the nebulous and sidereal condition. 



263 Stars of first magnitude. [See Phil. Trans., 1785, p. 68.] 



264 Prismatic analysis of the light of Sirius, a Orionis, Procyon, Arcturus^ 



Aldebaran and a Lyra'. 



265 X. Of the aggregation of stars. 



Star-gauges prove that the stars are not equally distributed over the 



celestial regions. [See Phil. Trans., 1785.] 

 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 clusters. 



Clusters in very rich parts of the heavens are generally of irregular 

 form and imperfectly collected. One hundred and twelve such ob- 



267 jects are referred to ; eighty of size not noted, fifty-three of bese in 

 the milky way, eighteen near it, nine at a distance from it Also 

 thirty-two irregular clusters from 2' to 30' in diameter; of these 

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



267 The .^reat number of clusters in these two collections is not only an 



indication that they owe their origin to a clustering power residing 

 n the centre ; but the still remaining irregularity of their arrange- 

 ment additionally proves that the action of the clus.enn^^^^^^^^^^ 

 has not been exerted long enough to produce a more artificial con- 



structiou. 



268 XII. Of clusters variously extended and compressed. 



Ffteen extended clusters named; twelve in the --^y^^^ 

 near it. Their descriptions show that the power whicdi has dra^ n 

 the stars together has acted under difierent circumstances m the 



several cases, 

 oro TTTT Of clusters of stars of a peculiar description. 

 "^ ^ "sniol'iccs i.u..d: one in ,bo milky way, three near .,, two at 



a distance from it. 

 071 XTV Of differently compressed clusters of stars. 



fhl;e hitherto only considered the arrangement of stars m clusters 



t h rt e v7o noint out whether they are drawn together by a 



cl IrinT-wer- in the same manner as the nebulous matter has 



