Clusters of Stars and Nebulce. 



CLUSTERS OF STAES AND NEBULAE.— THE 

 SURFACE OF THE MOON. 



BY THE REV. T. W. WEBB, M.A., F.R.A.S. 



Our recent survey, in these pages, of the more conspicuous 

 and interesting of the double and binary stars will, it may be 

 hoped, have led the astronomical inquirer to wish for a still 

 more extended knowledge of that glorious host of suns which 

 surrounds him in every direction. It will be our object to give 

 him such further assistance as we can in this noble pursuit, and 

 therefore, quitting for the present the branch of study which 

 has hitherto occupied us, we will choose a fresh point of view, 

 and proceed to the consideration of other and more compli- 

 cated arrangements. 



It is impossible to look upon the open heavens without an 

 instinctive conviction of the unequal distribution of the stars in 

 space; some regions are left comparatively vacant; in others, there 

 is a crowding together of stars so nearly corresponding in mag- 

 nitude as to leave no doubt as to their actual combination in 

 groups ; the individuals of which may possibly be separated by 

 distances baffling all human conception, but which yet show 

 mutual connection as compared with the void space surround- 

 ing them. Of course a similar appearance would be the result, 

 if they had only an optical and not a real proximity, being 

 merely arranged, nearly in the same direction with regard to 

 our sight. But in order to produce this effect, there would 

 necessarily be so strange a counterbalancing of distance and 

 brightness, that we perceive at once the improbability of such 

 an explanation. There are, no doubt, occasional instances of 

 apparent equality resulting from such compensations of re- 

 moteness by superior brilliancy, because amid the profusion of 

 the heavens there is room for every alternative; and, as it has 

 been truly observed, an event, against the probability of which 

 there are 10,000 chances to one, will yet actually occur, if it has 

 10,000 chances given to it. But still we shall be quite safe in 

 concluding that such instances of apparent proximity arc not 

 the rule but the exception, and that in the case of large aggre- 

 gations such an exception will approach impossibility. It 

 may be very possible with regard to any two equal and adjacent 

 stars, that their apparent neighbourhood maybe a deception, 

 from tin' compensation <>f brightness by distance; but the 

 probability of* such an arrangement will be much less where 

 three are concerned, and will very rapidly diminish with 

 increasing numbers. The evidence <>(* sense is fully in accord- 

 ance with this unquestionable deduction. Wo cannot look upon 

 the three well-known stars in the belt of Orion without a dis- 





