NOTES. 



(33 2 ) p. 201. Madler, Astr. S. 44? . 



( 333 ) p. 201. Arago in the Annuaire for 1842, p. 400. 



(334^ p^ 201. "An Inquiry into the probable Parallax and Magnitude. of 

 the fixed Stars, from the quantity of light which they afford us, and the par- 

 ticular circumstances of their situation, by the Rev. John Michell; in the 

 Phil. Trans. Vol. Ivii. p. 234261. 



( 335 ) p. 202. John Michell, same work, 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 . . . ." He denies throughout the whole discussion, that 

 one of two revolving stars can be a dark planet, reflecting light not its own, 

 since both are visible to us notwithstanding the distance. He compares both 

 the stars, the larger of which he calls the " Central Star," with the density of 

 our sun, and applies the term " Satellite" only for the purpose of conveying 

 the idea of revolution, or reciprocal motion. He speaks of the " greatest 

 apparent elongation of those stars that revolved about the others as satellites." 

 Further on he says, " 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 

 particular, 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." (Compare also Arago 

 in the Ann. 1834, p. 308, and in the Ann. 1842, p. 400.) No great weight 

 can be ascribed to the numerical results of the calculus of probabilities, as 

 given by Michell, taken separately ; as the suppositions laid down, that there 

 are in the entire heavens 230 stars equal in intensity of light to (3 Capricorni, 

 and 1500 equal to the light of the six larger Pleiades, are not at all correct. 

 The ingenious cosmological memoir of John Michell terminates with the very 

 hazardous attempt to explain the scintillation of the fixed stars by a kind of 

 " pulsation in material effluxes of light," an attempt as little fortunate as that 

 put forth by Simon Marius, one of the discoverers of Jupiter's satellites (Kos- 

 mos, Bd. ii. S. 357 and 509, Eng. ed. p. 316, note 484) at the end of his 

 Mundus Jovialis (1614). Michell, however, has the merit of having called 

 attention (p. 263) to the circumstance that scintillation is always combined 

 with change of colour ; " besides their brightness, there is in the twinkling of 

 the fixed stars a change of colour." (See Kosmos, Bd. iii. S. 122, Eng. ed. 

 note 129.) 



( 336 ) p. 203. Struve in the Recueil des Actes de la Seance publique da 



