676 THE POPULAR SCIENCE MONTHLY. 



capacious to gather the similarities of things unlike. To the imagina- 

 tive fervor of Kepler he joined the technical skill of Tycho, and some- 

 thing of the experimental sagacity of Galileo. Short as was his life, 

 and scanty his opportunities, he still left the imprint of his genius on 

 astronomical theory. The movements of the moon had not yet been 

 brought within the dominion of Kepler's Laws. Horrocks first pointed 

 out that the apparent irregularities of our satellite could be harmonized 

 into an orderly scheme, by supposing her to revolve in an ellipse of 

 which the earth occupied one focus the eccentricity of such ellipse 

 being variable, and its major axis directly rotatory. Both these con- 

 ditions Newton, in his investigation of the problem of three bodies, 

 demonstrated to follow necessarily from the law of gravitation, there- 

 by lending overwhelming corroboration to the views of his youthful 

 predecessor. It has been unwisely said that Newton was indebted to 

 Horrocks for the rudiments of his great generalization. No statement 

 could be more misleading. The passage in his writings principally re- 

 lied on for its support is indeed remarkable, as containing a description 

 of an ingenious experiment, illustrative of the confound nature of the 

 planetary movements, used afterward by Hooke, with a fuller under- 

 standing of the conditions of the problem ; and some scattered indica- 

 tions may be found that the analogy between terrestrial gravity and 

 the power exerted in the celestial mechanism was evident to him, as it 

 had been to Gilbert, Bacon, and Galileo ; but we are unable to dis- 

 cover that his idea of central forces was notably in advance of the 

 crude notions current among his contemporaries. 



Little as we know of Horrocks, we might easily have known no- 

 thing. His legacy to posterity barely escaped total annihilation. Some 

 of his papers were destroyed in the civil war ; some perished in the 

 great fire of London ; some were carried to Ireland, and there lost. 

 A remnant only was preserved by the care of William Crabtree, and 

 after his death (which followed quickly upon that of his friend) passed 

 into the hands of Dr. Worthington, of Cambridge. Hevelius, the cele- 

 brated astronomer of Dantzic, eventually obtained possession of his 

 "Venus in Sole visa," and published it in 1662, as an appendix to his 

 own observations on the transit of Mercury. Whereupon the Royal So- 

 ciety, awakening to the merits of their countrymen, commissioned one 

 of their most distinguished members to edit what could still be recov- 

 ered of his writings, and even voted, we are told, five pounds toward 

 the expense of printing. Dr. Wallis accomplished his task satisfac- 

 torily. The disjecta membra of the Horroxian manuscripts, organized 

 into a tolerably consistent form under the title " Astronomia Keple- 

 riana Defensa et Promota," were given to the public in 1672, together 

 with those fragments of his correspondence with Crabtree which, dis- 

 guised in the uncouth Latin of the Savilian professor, constitute all 

 our knowledge of the life of Jeremiah Horrocks. 



We have already seen that his scientific enthusiasm was not an 



