22 .4 Yorkshire Rector of the Eighteenth Century. 



an instrument of supreme value in physical research seeing 

 that it affords the standard method for the determination of 

 very small forces. 



III. — CoXTRIBUTIOxVS TO AsTKONOMY. 



Probably from an early period in his career Michell included 

 in the wide circle of his pursuits the practical study of the 

 heavens. His earliest communication to the Royal Society 

 was made in the year 1760 and had for its title ' Observations 

 on the Comet of 1760.'* He constructed his own reflecting 

 telescope, and put it to such good use as enabled him to make 

 important additions to astronomy. His papers in this depart- 

 ment of science are marked by the same originality of conception 

 which, as we have seen, is so manifest in his other researches. 

 They gained for him the respect and esteem of his contempor- 

 aries, but their merit and the remarkable prescience wherewith 

 he sometimes foreshadowed in them some of the discoveries 

 of later generations have not until recently been perceived. 



Especially memorable is the paper which he read to the 

 Royal Society in 1767, with the title of ' An Enquiry 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.'! This memoir affords 

 striking evidence of its author's prowess both as a careful 

 observer of fact, and as a philosopher who could discuss with 

 great breadth of view, perspicacity and originalitv the problems 

 which the observations presented. He was here the first to 

 suggest that the close proximity of the constituent members 

 of double stars is owing to some physical connection existing 

 between them. He likewise initiated the employment of 

 mathematical micthods depending on probability and statistics 

 in the discussion of the theory of the distribution of the stars 

 in the firmament, i His important discovery of the existence 

 of stellar groups was appreciatively acknowledged by his 

 great contemporary Wilham Herschel, who referred to Michell's 

 ' elegant proof of it on the computation of probabilities. '§ 



In a subsequent paper which took the form of a letter to 

 his friend Henry Cavendish, and was published in 1784,11 ' he 

 expressed his firm conviction that the double and triple stars 

 discovered by Herschel were so many systems of stars, so 

 near to each other as to be liable to be affected by their mutual 

 gravitation, and he considered it as not unhkely that the 

 periods of the revolutions of some of these about their principals 



* Phil. Ti'iius., Yo]. 51, p. 466. 



t Phil. Trans., Vol. 37, p. 234. 



X R. Grant, History of Physical Astronomy, p. 559. 



§ Phil. Trans., Vol. 75 (1875). 



II Phil. Trans., Vol. 74 (1784), p. 33. 



Naturalist^ 



