Besohable NeLulue. 313 



sphere in a state of equal concentration. The rapid aug- 

 mentation of intensity towards the centre, the presence of 

 a kind of luminous nucleus in the centre itself, prove that 

 the stars are more condensed there, and around it, than in any 

 other place. Such a result is important, at once by its nature 

 and its generality. It ought to be considered as an obvious 

 indication of the existence of a clustering power directed from 

 all parts towards the centre of the globular group. 



Number of stars contained in certain globular Nebula. — It 

 would be impossible to give a detailed and exact enumeration 

 of the total number of stars of which certain globular nebulae 

 are composed ; but we may arrive at certain limits. By tak- 

 ing account of the angular spacing of the stars situate near the 

 edges — that is to say, in the region where they do not project 

 one over another, and comparing it with the total diameter of 

 the group, we ascertain that a nebula, whose diameter is about 

 10 minutes, and whose apparent superficial extent is scarcely 

 equal to a tenth of that of the lunar disc, contains no less than 

 twenty thousand stars. 



The dynamical conditions fitted to secure the indefinite pre- 

 servation of such a multitude of stars, cannot easily be ima- 

 gined. Are we to suppose that the system is in repose ? The 

 stars would in time fall upon each other. Are we to assign 

 to them a rotatory movement round a single axis ? Shocks 

 would become inevitable. Further, is it proved, a priori^ that 

 the globular systems of stars must be preserved indefinitely in 

 the state in which we now see them ? 



Perforated or Annular Nebulcd. — Herschel classed among 

 the curiosities of the firmament a nebula previously inserted 

 under No. 57 in the old catalogue of the Connaissancc des 

 Temps. But that justice may be done, let us hasten to add 

 that Messier and Mechain, with their feeble glasses, had nei- 

 ther perceived any star in the nebulosity, nor discerned its 

 real form. 



This nebula appears as a somewhat elliptical ring of stars. 

 A dark hole is seen in the centre. The two axes are in the 

 proportion of 83 to 100. The obscure opening occupies about 

 the half of the diameter of the nebula. 



VOL. XXXIII. NO. LXVI. OCTOBER 1842. X 



