NEBULAR HYPOTHESIS 



counter-generalization. The fact is, that the nebula? were 

 always understood to be of two kinds : 1, nebulae which 

 were only distant clusters, and which yielded, one afte: 

 another, to the resolving powers of telescopes, as these 

 powers were increased; 2, nebulae comparatively near 3 

 which no increase of telescopic power affected. Two 

 classes of objects wholly different were, from their partial 

 resemblance, recognised by one name, and hence the con- 

 fusion which has arisen upon the subject. The resolution 

 of a great quantity of the first kind of nebula? by Lord 

 Rosse's telescope was of course expected, and it is a fact, 

 though in itself interesting, of no consequence to the neb 

 ular hypothesis. It will be only in the event of the sec- 

 ond class being also resolved, and its being thus shown 

 that there is only one class of nebula?, that the hypothesis 

 will suffer. Such, at least, I conclude to be the sense of 

 a passage which I take leave to transfer, in an abridged 

 form, from a recent edition of Professor Nichol's work 



" I. By far the greater number of the milky streaks, or spots, 

 whose places have hitherto been recorded, lie at the outermost, or 

 nearly at the outermost boundary of the sphere previously reach- 

 ed by our telescopes ; and in this case there is no certain principle 

 on the ground upon which a pure nebula can be distinguished 

 from a cluster so remote that only the general or fused light of its 

 myriads of constituent orbs can be seen. Sometimes—resting on 

 a peculiarity of form or other characteristic — the astronomer may 

 venture a guess that such an object is probably a firmament ; as, 

 indeed, I was bold enough to do in former editions of this work 

 with regard to several which have since been resolved ; but in 

 the main he can tell little concerning them, or have any other 

 belief than that, as with similar masses near him, a great, proba- 

 bly the greater number, are true clusters, grand arrangements of 

 stars, incredibly remote, but resembling in all things our cwn 

 home galaxy. Now the application to such objects of a new and 

 enlarged power of vision could be attended only by one result — 

 magnificent, but far from unexpected : and it is here that the six 

 feet mirror has achieved its earliest triumphs. Under its piercing 

 glance, great numbers of the milky specks have unfolded their 

 starry constituents ; some of these, which previously were almost 

 unresolved, shining with a lustre equivalent to that of our bright- 

 est orbs to the naked eye. How far it will go with its resolving 

 power has not yet been ascertained ; but I perceive that Sir James 

 South has given his authority that some spots examined by it con- 

 tinue intractable. 



" II. The influence of the new discoveries either to impair or 

 strengthen the foundations of the nebular hypothesis, must clearly 

 be looked for among their bearings on less remote and ambiguous 

 objects. Now the new aspects of these may lead us to question 

 our former opinions a? to the existence of the supposed filmy self, 

 luminous masses ; or they may throw doubt on the reality of thoas 



