xii.] THE INDUCTIVE OR INVERSE METHOD. 247 



human origin of the flint flakes so copiously discovered of 

 late years. For though the accidental stroke of one stone 

 against another may often produce flakes, such as are 

 occasionally found on the sea-shore, yet when several 

 flakes are found in close company, and each one bears 

 evidence, not of a single blow only, but of several suc- 

 cessive blows, all conducing to form a symmetrical knife- 

 like form, the probability of a natural and accidental 

 origin becomes incredibly small, and the contrary suppo- 

 sition, that they are the work of intelligent beings, 

 approximately certain. 1 



The Tlieory of Probability in Astronomy. 



The science of astronomy, occupied with the simple 

 relations of distance, magnitude, and motion of the 

 heavenly bodies, admits more easily than almost any 

 other science of interesting conclusions founded on the 

 theory of probability. More than a century ago, in 

 1767, Michell showed the extreme probability of bonds 

 connecting together systems of stars. He was struck 

 by the unexpected number of fixed stars which have 

 companions close to them. Such a conjunction might 

 happen casually by one star, although possibly at a 

 great distance from the other, happening to lie on a 

 straight line passing near the earth. But the probabilities 

 are so greatly against such an optical union happening 

 often in the expanse of the heavens, that Michell asserted 

 the existence of some connection between most of the 

 double stars. It has since been estimated by Struve, 

 that the odds are 9570 to I against any two stars of not 

 less than the seventh magnitude falling within the appa- 

 rent distance of four seconds of each other by chance, and 

 yet ninety-one such cases were known when the estimation 

 was made, and many more cases have since been discovered. 

 There were also four known triple stars, and yet the odds 

 against the appearance of any one such conjunction are 

 I 73 > 5 2 4 to i. 2 The conclusions of Michell have been 



1 Evans' Ancient Stone Implements of Great Britain. London, 

 1872 (Longmans). 



2 Herschel, Outlines of Astronomy, 1849, p. 565 ; but Todhunter, 

 in his History of the Theory of Probability, p. 335, states that the 

 calculations do not agree with those published by Struve. 



