604 BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 



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



A. D. Vol. P. 



been proved to be condensed by a gravitating principle; bat in tbo 

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

 it is one and the same power uniformly exerted which first con- 

 densed nebulous matter into stars and afterwards draws them to- 

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

 gradually increases the compression of the stars which form the 

 clusters. The first collection has thirty-three considerably com- 

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

 one at a distance. The second collection contains eight clusters, 

 highly compressed, five in the milky way, two near it, and one at a 

 distance. 

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



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

 as in the thirty-nine clusters given in the folloAving 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 the 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. 



5G; 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 way, 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 

 which they are composed are more minute than those of the clusters 

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

 closer, and the 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 difference which there may be in different clusters, not only 

 in the size, but also in the 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 which was a brilliant globular cluster of stars, the second 

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

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

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

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

 the milky way. 



XIX. Of a recurrence of the ambiguotts 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. 



