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."[1]
Of Hooke's private and personal history there is little to be recorded. His life might almost be comprised in two words—experiments 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[2] 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 publication 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 direction 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 vibrative 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."[3]
Further, he hit upon the principle of "interference," which, neg-
