274 COSMOS. 



Michell* who was not acquainted with the ideas of Kant and 

 Lambert, was the first who applied the calculus of proba- 

 bilities to small groups of stars, which he did with great 

 ingenuity, especially to multiple stars, both binary and qua- 

 ternary. He showed that it was 500000 chances to 1 that 

 the collocation of the six principal stars in the Pleiades did 

 not result from accident, but that, on the contrary, they owed 

 their grouping to some internal and reciprocal relation. He 

 was so thoroughly convinced of the existence of luminous stars, 

 revolving round each other, that he ingeniously proposed to 

 employ these partial star-systems to the solution of certain 

 astronomical problems. 7 



* An Inquiry into the probable parallax and magnitude 

 of the fixed stars, from the quantity of light which they afford 

 us, and the particular circumstances of their situation, by 

 the Rev. John Mitchell ; in the Philos. Transact., vol. Ivii. 

 pp. 234-261. 



7 John Michell, ibid., p. 238. " If it should hereafter be 

 found that any of the stars have others revolving about them 

 (for no satellites by a borrowed light could possibly be visible], 



we should then have the means of discovering " 



Throughout the whole discussion he denies that one of the 

 two revolving stars can be a dark planet shining with a 

 reflected light, because both of them, notwithstanding their 

 distance, are visible to us. Calling the larger of the two the 

 " Central Star," he compares the density of both with the 

 density of our sun, and merely uses the word " satellite " 

 relatively to the idea of revolution, or of reciprocal motion ; 

 he speaks of the " greatest apparent elongation of those 

 stars, that revolve about others as satellites." He fur- 

 ther says, at pp. 243 and 249 : " We may conclude with the 

 highest probability (the odds against the contrary opinion 

 being many million millions to one) that stars form a kind of 

 system by mutual gravitation. It is highly probable in par- 

 ticular, and next to a certainty in general, that such double 

 stars as appear to consist of two or more stars placed near 

 together are under the influence of some general law, such 

 perhaps as gravity r ' (Consult also Arago, in the 



