292 COSMOS 



conclusions regarding the non-existence of all nebula?, and 

 indeed of all cosmical vapour generally. But whether these 

 well-defined nebulous spots be a self-luminous vapoury matter, 

 or remote, closely-thronged globular clusters of stars, they 

 must ever remain objects of vast importance in the knowledge 

 of the structure of the universe and of the contents of space. 



The number whose positions have been determined by 

 right ascension and declination, exceeds 3,600. Some of 

 the more irregularly diffused, measure eight lunar diame- 

 ters. According' to William Herschel's earlier estimate, 

 made in 1811, these nebulous spots cover at least 2-f^th 

 part of the whole visible firmament. As. seen through 

 colossal telescopes, the contemplation of these nebulous masses 

 leads us into regions from whence a ray of light, according to 

 an assumption not wholly improbable, requires millions of 

 years to reach our earth, to distances for whose measurement 

 the dimensions (the distances of Sirius, or the calculated 

 distances of the binary stars in Cygnus and the Centaur) 

 of our nearest stratum of fixed stars scarcely suffice. If 

 these nebulous spots be elliptical or spherical sidereal 

 groups, their very conglomeration calls to mind the idea 

 of a mysterious play of gravitating forces by which they 

 are governed. If they be vapoury masses, having one or 

 more nebulous nuclei, the various degrees of their conden- 

 sation suggest the possibility of a process of gradual star- 

 formation from inglobate matter. No other cosmical structure 

 no other subject of this branch of astronomy more contem- 

 plative than measuring is, in like degree, adapted to excite 

 the imagination, not merely as a symbolic image of the infi- 

 nitude of space, but because the investigations of the different 

 conditions of existing things, and of their presumed connection 



a Cosmos, vol. i. p. 63. 



