THE ENGLISH PRECURSORS OF NEWTON. 787 



had the same thoughts of a conjecture to find out a help for the eye to 

 see the smaller parts and rocks of the moon," and " would fain persuade 

 myself against concluding or building on the impossibility of such 

 things as I am not able demonstrably to prove not possible." * 



Of Hooke's private and personal history there is little to be re- 

 corded. His life might almost be comprised in two words experi- 

 ments and controversies. In 1664 Sir John Cutler instituted, especially 

 for his benefit, a mechanical lecturership of fifty pounds a year ; in 

 the following year he was appointed to the professorship of Geometry f 

 founded by Sir Thomas Gresham in 1575. His services as curator 

 were remunerated by an annual stipend of thirty pounds, not perhaps 

 very regularly paid, since we hear, on one occasion, that both he and 

 Halley were offered, in lieu of their respective salaries, an equivalent 

 number of copies of that unlucky " History of Fishes," by the publica- 

 tion of which the Royal Society had drained their finances and cumbered 

 their shelves. The famous controversy between Hooke and Hevelius 

 on the subject of plain or telescopic sights, which agitated the learned 

 world of Europe during many years, has long ago sunk into a silence 

 we need not disturb. Hevelius was in the wrong, and obstinate ; 

 Hooke was in the right, but offensive. Astronomers in general seemed 

 disposed to prefer some slight uncertainty as to the position of the 

 stars, to being bullied into precision by the magisterial little hunchback 

 of Gresham College. The dispute remained long in the condition of 

 a smoldering flame, with outbreaks of argument at distant intervals, 

 and Halley's mission of conciliation in 1679 helped to soothe the vanity 

 of the irritated philosopher of Dantzic, but did not tend to rectify his 

 method. 



We now come to the relations of Hooke with Newton. The first 

 collision between these two remarkable men occurred on the subject 

 of their respective optical discoveries. Hooke's merits in this direc- 

 tion were very considerable. He was the first to propound that view 

 as to the nature of light now universally accepted under the name of 

 the "undulatory theory." He held that light is a "very short vibra- 

 tive motion," originating in an agitation of the minute particles of the 

 luminous body, and propagated through a perfectly homogeneous and 

 elastic medium " by direct or straight lines, extended every way, like 

 rays from the center of a sphere, . . . just after the same manner 

 (though indefinitely swifter) as the waves or rings on the surface of 

 the water do swell into bigger and bigger circles about a point of it, 

 where by the sinking of a stone the motion was begun." J 



Further, he hit upon the principle of " interference," which, neg- 



* " Of the True Method of building a Solid Philosophy," " Posthumous Works," 

 p. 39. 



f Hooke read the " Gresham Lectures on Astronomy " in 1664-65, during the absence in 

 Italy of Professor Pope ; but never occupied that chair except as locum tenens. 



\ " Micrographia," pp. 56, 57. 



