Clusters and Nebulae. 211 



there can be no question that it indicates an amount of 

 light, and probably of heat and all other solar influences, 

 strangely contrasted with the condition of our solitary and 

 partially illuminated system. Here, however, we live, and 

 enjoy existence; there, in all probability, encompassed by 

 suns in every direction, we should soon perish in the blaze. 

 But these clusters are not only objects of the highest magni- 

 ficence, but of profound mystery as to their mode of persistence. 

 From the orbital motions of binary stars, as well as from all con- 

 siderations of analogy, we are led to infer a diffusion of gravity 

 as universal as that of light ; but, if so, these glorious agglo- 

 merations of suns must be in a state of progressive collapse, 

 and advancing, however slowly, yet with gradually accelerated 

 speed, to final destruction, or transformation into some wholly 

 new form of being. Nothing but the centrifugal force pro- 

 duced by rotation is capable, under any known circumstances, 

 of averting this catastrophe. Such would be the certain fate 

 of the whole planetary system, such in all probability that of 

 the binary suns, if rotation were to cease to exist. But how 

 rotation can exist in these clusters is a most perplexing 

 question. Sir J. Herschel, who says that " it is difficult to form 

 any conception of the dynamical state of such a system," has 

 indeed pointed out certain conditions under which an aggrega- 

 tion of this kind might maintain its stability, every separate star 

 describing its own elliptical orbit around the common centre 

 of gravity, and all of them returning, after a certain period, to 

 their original situations. But those conditions, as far as our 

 vision can inform us, are most improbable. It would be re- 

 quired that the space occupied should be a sphere, and that 

 the stars should be all equal and uniformly arranged. No 

 such specimen of symmetry seems to be known, while the 

 instances to the contrary are numerous, and the increase of 

 optical power usually adds to the irregularity of their aspect. 

 And even were those improbable conditions fulfilled, Sir J. 

 Herschel himself, in acknowledging that the law of periodicity 

 would not comprise the external stars, seems to admit an 

 element of disturbance and change, and ultimate ruin. It 

 would perhaps be going too far to pronounce a definitive 

 opinion in such a case, but it is not easy to escape from the con- 

 clusion that either gravity is not universally diffused, or the stars 

 are formed of imponderable matter (both of which suppositions 

 are strongly contradicted by analogy), or these systems contain 

 within themselves the germs of destruction, a catastrophe not 

 the less inevitable in the end, because the ephemeral existence 

 of man may possibly never permit him to obtain evidence of 

 its progress. 



vol. vi. — NO. in. P 



