262 Clusters and Nebula:. 



were all aggregations of stars of incalculable remoteness ; but 

 lie had subsequently found bright stars so accurately centred in 

 circular haze, that it was most improbable that the effect should 

 be due to a mere perspective projection of the one upon the 

 other; he had noticed other instances of nebulae whose shape 

 seemed remarkably accommodated to the position of stars, which 

 must have been, it would seem, actually not optically adjacent ; 

 he had ascertained that the great nebulas in Orion and Andro- 

 meda, brilliant enough to strike the unaided eye, and whose 

 starry nature ought therefore to have been most apparent of 

 all, were utterly irresolvable even in his gigantic telescopes ; he 

 had noticed in the former of these the combination of the 

 brightest and the faintest nebulosity, and hence perceived that, 

 contrary to all his former conclusions, ( ' the range of the visi- 

 bility of the diffused nebulous matter cannot be great ;" and 

 from an extended comparison of a series of circular irresolvable 

 nebulas, in the separate individuals of which central condensation 

 and brilliancy gradually increased till it assumed a star-like 

 character, he concluded that we thus had before our eyes at 

 once the whole process by which a thin luminous haze is com- 

 pressed into a naming sun. This was the basis of the celebrated 

 ' ' Nebular Hypothesis," which in the hands of Laplace assumed 

 such an extended development, and professed to account for 

 not merely the creation of suns from self-luminous mists, but 

 the formation of planets from rings of nebulous matter dropped 

 off from these suns during the process of condensation, and of 

 satellites in turn from the planets as they shrank into solidity. 

 To some minds, speculations of this nature, however visionary, 

 are so attractive that they become insensible to their attendant 

 difficulties ; others, on the contrary, incapable perhaps of 

 originating such theories, are much more sensible of their 

 weakness. However, the hypothesis in the present instance, as 

 we have seen, was not without plausibility, and it seemed to 

 rest on a substratum of something like fact, so long as the 

 telescopes of Herschel I. were unrivalled in that light- grasping 

 power which is so essential in these researches. But an appeal 

 lay to the future ; and the results of that appeal, while they 

 have shaken rudely the foundation, have but introduced addi- 

 tional mystery. Schroter had suspected that his 18-inch 

 speculum was beginning in some spots to approach the re- 

 solvability of the nebula; but his skill in this Jdiid of obser- 

 vation was not great, if we may judge from the figure he has 

 given. Herschel II. found it impracticable with a similar 

 aperture in 1 > v 2 I . I iasseU, with his magnificent 24-inch mirror, 

 had no hope, in 1817, of the absolute resolution of even the 

 principal part; and the purer skies of Malta, in 1852, and a 

 power of 1018, did not enable him to break up the " wool-like 



