SECT. XXXVI. FORMS OF NEBULA. 415 



clered still more so by their mode of association, and by the peculiar 

 features assumed by the Milky Way, which are without a parallel 

 for richness and magnificence in any other part of the sky. Some 

 of the globular clusters are so remote that the stars are scarcely 

 discernible mere star dust. There is a double globular cluster 

 in the southern hemisphere of very small dimensions, separated 

 by a minute interval, a combination which suggests the idea of 

 a globular cluster revolving about a very oblate spheroidal one in 

 the plane of the equator, and in an orbit which is circular, and 

 seen obliquely like the central nebula itself, with a diameter 

 somewhat more than four times the latter, a stupendous system 

 doubtless, but of which the reality can hardly be supposed 

 improbable. 



There appears to be some connexion between ellipticity of form 

 and difficulty of resolution, for spherical clusters are in general 

 easily resolved into their component stars, while there is scarcely 

 an instance of an elliptical cluster yielding except to a very high 

 optical power. Vast masses of the nebulas have never been re- 

 solved. Lord Rosse's great telescope has resolved parts of the 

 nebula of Orion, and various others which had not yielded to in- 

 struments of less power ; it enables the astronomer to penetrate 

 farther into space, and shows objects with greater clearness, than 

 any other. But, excellent as this instrument is, thousands of 

 nebulse are not to be resolved even by it. Those who imagine that 

 any work of man can resolve all the nebulous matter in the 

 heavens must have a very limited idea of the extent and sublimity 

 of creation. 



Innumerable nebulaa in both hemispheres take the form of 

 clusters of stars, but are totally different from the globular clus- 

 ters, inasmuch as thej^are of irregular form and follow no uniform 

 law of condensation. The Pleiades is an instance in our own 

 stellar system ; for although only 7 or 8 stars are visible to the 

 naked eye, telescopes show that more than 200 belong to the 

 group. In the constellation Cancer there is a luminous spot called 

 the Prsesepe or Beehive, which a very low power resolves into 

 stars ; and the constellation Coma Berenices is another stellar 

 group. Many are of exquisite beauty, as that round a Crucis, 

 which, though consisting of only a hundred and ten stars, is like 

 apiece of fancy jewellery, from the colours of the stars, which are 

 greenish white, green, blueish green, and red. Many of these 



