NEBULAR HYPOTHESIS. 



207 



forms and densities of cometic nuclei. Sir William Herschel cer- 

 tainly was not ignorant that round or spherical clusters abound in 

 the skies, which, when first seen, present all the appearances ot 

 such nebula?— nay, he grounded on the fact of their approximate 

 sphericity and varying degrees of concentration some of the 

 boldest and most engrossing of his conjectures ; nor would he 

 have doubted that multitudes which, even to his instruments, 

 seemed only general lights, would, in after times, be resolved ; but 

 here, as before, the gist of the question is not, can you resolve 

 round nebulae never resolved before ; but can you resolve such as, 

 quite within the range of former vision, have_ continued intracta- 

 ble under the scrutiny of powers which, judging from the aver- 

 age of our experience, must surpass what ought to have resolved 

 them ? 



" Such are my views as to the present condition of this impor- 

 tant question ; and if they are correct, it will, appear that, not- 

 withstanding the resolutions achieved by the new instruments, 

 they are, as yet, quite as likely — by accumulating new objects 

 belonging to the three foregoing classes, and by more surely and 

 distinctly establishing their characteristic features — to strengthen, 

 as to invalidate the grounds of the nebular hypothesis. Eagerly, 

 but patiently, let us watch the approaching revelations." 



Various minor objections have been presented to the 

 nebular hypothesis ; but, before adverting to any of them, 

 I may give a brief abstract of certain recent experiments, 

 by which it has been remarkably illustrated. Here it is 

 peculiarly important to bear in mind that the phenomena 

 of nature are, if I may so speak, indifferent to the scale 

 on which they act. The dew-drop is, in physics, the 

 picture of a world. Remembering this, we are prepared, 

 m some measure to hear of a Belgian professor imitating 

 the supposed formation and arrangement of a solar sys- 

 tem, in some of its most essential particulars, on the table 

 d{ a lecture-room ! The experiments were first con- 

 ducted by Professor Plateau of Ghent, and afterwards re- 

 peated by our own Dr. Faraday. 



The following abstract of Professor Plateau's experi- 

 ments is also presented in the fifth edition of the Vestiges. 

 Its being repeated here is, that it may meet the eyes of 

 many who are not likely to see any edition of that work 

 nesides those from which it is absent : 



Placing a mixture of water and alcohol in a glass box, 

 and therein a small quantity of olive oil, of density pre- 

 cisely equal to the mixture, we have in the latter a liquid 

 mass relieved from the operation of gravity, and free to 

 take the exterior form given by the forces which may act 

 upon it. In point of fact, the oil instantly takes a globu 

 lar form by virtue of molecular attraction. A vertica* 



