702 THE UNIVERSE. 



thest distances in the heavens white patches of different 

 shapes, which were long regarded as simple cosmical, phos- 

 phorescent vapors, or as germs of the universe ready to be 

 condensed into new worlds. It is to these white gleams 

 that the name of nebulce was given, in order to designate 

 their diffused appearance and the uncertainty of their na- 

 ture. But by means of newly invented powerful instru- 

 ments it has been made out that these luminous clouds, in 

 which it was thought man had discovered globes in the 

 process of formation, are only groups of small telescopic 

 stars, often aggregated in considerable numbers, and assum- 

 ing the most varied and unexpected figures. 



Some nebulae are nearly globular ; others, like those in the 

 constellations of the Virgin and the Greyhounds, are like a 

 spiral whirlwind ; and there are some which resemble a ring. 



scopes, are resolved into clusters of stars when seen through a telescope of suffi- 

 cient power; but there is likewise a class of nebulae which cannot be resolved into 

 star-clusters, being shown by the spectroscope to consist of masses of glowing or 

 incandescent gas. To these latter bodies the term nebulae would be more strictly 

 applicable, but at present both classes are called by the same name, though so dif- 

 ferent in constitution. The number of nebulae at present known amounts to some- 

 where about 5700. Sir W. Herschel discovered 2500 nebulae; his son, Sir John, 

 revising his father's work, discovered 500 more, and, proceeding to the Cape of 

 Good Hope, added 1 700 southern nebulae to the list. Mr. Huggins first success- 

 fully applied the spectroscope to nebulae. In August, 1864, he first turned his 

 stellar spectroscope on a planetary nebula in the constellation Draco. To his as- 

 tonishment he found it to consist of an incandescent mixture of the gases hydro- 

 gen and nitrogen. He has since examined the spectra of a great number of these 

 objects. Of the twenty which he had examined in 1870, about one third are 

 evidently gaseous. It is found that the close association of points of light in a 

 nebula must not be accepted as an indication of resolvability into stars, for these 

 luminous points in many cases only indicate the existence of places of greater 

 gaseous density than common. See art. Nebula in the Popular Encyclopedia 

 (Blackie & Son). 



