Page:Popular Science Monthly Volume 17.djvu/694

676 capacious to gather the similarities of things unlike. To the imaginative fervor of Kepler he joined the technical skill of Tycho, and something 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 conditions Newton, in his investigation of the problem of three bodies, demonstrated to follow necessarily from the law of gravitation, thereby 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 relied 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 understanding of the conditions of the problem; and some scattered indications 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 discover 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 nothing. 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 celebrated 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 Society, awakening to the merits of their countrymen, commissioned one of their most distinguished members to edit what could still be recovered of his writings, and even voted, we are told, five pounds toward the expense of printing. Dr. Wallis accomplished his task satisfactorily. The disjecta membra of the Horroxian manuscripts, organized into a tolerably consistent form under the title "Astronomia Kepleriana Defensa et Promota," were given to the public in 1672, together with those fragments of his correspondence with Crabtree which, disguised 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