12 EXPLANATIONS. 



we had ventured to suppose, — and certainly we shall then 

 hesitate in averring further, concerning the existence or at 

 least the diffusion of the purely nebulous modification of 

 matter. 



"2. Lord Rosse's telescope may also, as I have said, dis- 

 prove the reality of our arrangement of the forms of the 

 nebulge as steps of a progression. And in regard of this 

 question, there seem two classes of objects meriting attention. 



" First, I shall refer to the nebulous stars properly so 

 called, or to that form in which the diffused matter has 

 reached the condition of almost pure fixed stars. Now, of 

 these objects there are two distinct sets, presenting at first to 

 the telescope very much the same appearance, but in regard 

 of which our knowledge is very different. It will readily be 

 conceived that a distant cluster, with strong concentration 

 about the centre of its figure, must, to the telescope which 

 first descries it, look like a star with a halo around it. When 

 a higher power is applied, that central star, however, will 

 appear as a disc, and to a still higher power the cluster will 

 be revealed. A very great number of what are called nebulous 

 stars, are doubtless of this class ; and we have hitherto had 

 no means of accurately ascertaining the fact, just because our 

 largest telescopes were required to descry them ; but there 

 are multitudes of others — the true ' photospheres' — quite of a 

 different description. Many of these are easily seen as fixed 

 stars with haloes of different sizes diminishing to the mere 

 ' bur ;' and under the greatest power as yet applied, the 

 apparent central star never expands into a disc, or departs 

 from the stellar character. It is by its effect on these that 

 the new instrument will at all bear on this portion of the 

 nebular hypothesis. 



" Secondly, The foregoing being our grounds of belief in 

 the existence of nebulae — first, in a diffused or chaotic state. 



