604 BIBLIOGEAPHY OF HERSCHEl's WEITINGS. 



Herschel, W.: Synopsis of the Writings of— Continued. 

 A. D. Vol. p. 



been proved to be condensed by a gravitating principle ; but in tbe 

 forty-one clusters of tbe following two collections we shall see that 

 it is one and tbe same j)owcr uniformly exerted wbicb first con- 

 densed nebulous matter into stars and afterwards draws tbem to- 

 gether into clusters, and wbicb, by a continuance of its action, 

 gradually increases tbe compression of tbe stars wbicb form tbe 

 clusters. Tbe first collection bas tbirty-tbree considerably com- 

 pressed clusters, seventeen in tbe milky way, fifteen near it, and 

 one at a distance. Tbe second collection contains eigbt clusters, 

 bigbly compressed, five in tbe milky way, two near it, and one at a 

 distance. 

 1814 104 272 XV. Of the gradual concentration and insulation of clusters of stars, 



Tbe existence of a clustering power is nowhere so visibly pointed out 

 as in the thirty-nine clusters given in tbe following collection: 

 Twenty-one of these are in the milky way, seven near it, and eleven 

 at a distance. 

 273 XVI. Of globular clusters of stars. 



Fourteen such objects noted: One in tbe milky way, four near it, and 

 nine at a distance from it. 

 274-7 [Detailed accounts from observing books of M. 72; M. 2; M. 5; M. 



50; M. 80; M. 13; M. 3; M. 15; M. 79; M. 19; M. 53.] 

 278 XVII. Of more distant globular clusters of stars. 



The following eleven objects are so like those of the foregoing col- 

 lection that I have called them miniatures of the former. Five of 

 these are in the milky wa;y, one near it, and five at a distance. De- 

 tailed descriptions given. 

 279 I have supposed the clusters of this class to be at a greater distance 

 from us than those of the preceding collection, because the stars of 

 wbicb they are composed are more minute than those of tbe clusters 

 of which I have called them miniatures ; their compression is also 

 closer, and tbe size of the whole is much contracted, all of which 

 particulars are readily explained by admitting them to be more dis- 

 tant. This argument, however, does not extend so far as to exclude 

 a real ditfereuce which there may be in different clusters, not only 

 in tbe size, but also in tbe number and arrangement of the stars. 



XVIII. Of still more distant globular clusters of stars. 



280 It has frequently happened that I saw three objects in succession, the 



first of wbicb was a brilliant globular cluster of stars, the second 

 a miniature of tbe former in wbicb the stars could just be perceived, 

 and the third in every respect a similar miniature of tbe second, as 

 the second was of the first, but in which tbe stars, though suspected, 

 were no longer to be distinguished. Five such objects given, all in 

 the milky way. 



XIX. Of a recurrence of the ambiguous limit of observation, 



281 It has already been shown [VIII, p. 259] that in passing from faint 



nebulosity to the suspected sidereal condition we cannot avoid meet- 

 ing with ambiguous objects, and the same critical situation will 

 again occur, when, from the distinctly sidereal appearance, we en- 

 deavor to penetrate gradually further into space. 

 The effects of clustering power have been gradually traced from the 

 first indication of clustering stars through irregular as well as 

 through more artificially arranged clusters up to the beautiful 

 globular form. 



