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Rh pursued amid innumerable difficulties his purpose of self-education. His university career lasted three years, and on its termination he became a tutor at Toxteth, devoting to astronomical observations his brief intervals of leisure. In 1636 he met with a congenial spirit in William Crabtree, a draper of Broughton, near Manchester; and encouraged by his advice he exchanged the guidance of Philipp von Lansberg, a pretentious but inaccurate Belgian astronomer, for that of Kepler. He now set himself to the revision of the Rudolphine Tables (published by Kepler in 1627), and in the progress of his task became convinced that a transit of Venus overlooked by Kepler would nevertheless occur on the 24th of November (O.S.) 1639. He was at this time curate of Hoole, near Preston, having recently taken orders in the Church of England, although, according to the received accounts, he had not attained the canonical age. The 24th of November falling on a Sunday, his clerical duties threatened fatally to clash with his astronomical observations; he was, however, released just in time to witness the punctual verification of his forecast, and carefully noted the progress of the phenomenon during half an hour before sunset (3.15 to 3.45). This transit of Venus is remarkable as the first ever observed, that of 1631 predicted by Kepler having been invisible in western Europe. Notwithstanding the rude character of the apparatus at his disposal, Horrocks was enabled by his observation of it to introduce some important corrections into the elements of the planet’s orbit, and to reduce to its exact value the received estimate of its apparent diameter.

After a year spent at Hoole, he returned to Toxteth, and there, on the eve of a long-promised visit to his friend Crabtree, he died, on the 3rd of January 1641, when only in his twenty-second year. To the inventive activity of the discoverer he had already united the patient skill of the observer and the practical sagacity of the experimentalist. Before he was twenty he had afforded a specimen of his powers by an important contribution to the lunar theory. He first brought the revolutions of our satellite within the domain of Kepler’s laws, pointing out that her apparent irregularities could be completely accounted for by supposing her to move in an ellipse with a variable eccentricity and directly rotatory major axis, of which the earth occupied one focus. These precise conditions were afterwards demonstrated by Newton to follow necessarily from the law of gravitation.

In his speculations as to the physical cause of the celestial motions, his mind, though not wholly emancipated from the tyranny of gratuitous assumptions, was working steadily towards the light. He clearly perceived the significant analogy between terrestrial gravity and the force exerted in the solar system, and by the ingenious device of a circular pendulum illustrated the composite character of the planetary movements. He also reduced the solar parallax to 14″ (less than a quarter of Kepler’s estimate), corrected the sun’s semi-diameter to 15′ 45″, recommended decimal notation, and was the first to make tidal observations.

Only a remnant of the papers left by Horrocks was preserved by the care of William Crabtree. After his death (which occurred soon after that of his friend) these were purchased by Dr Worthington, of Cambridge; and from his hands the treatise Venus in sole visa passed into those of Hevelius, and was published by him in 1662 with his own observations on a transit of Mercury. The remaining fragments were, under the directions of the Royal Society, reduced by Dr Wallis to a compact form, with the heading Astronomia Kepleriana defensa et promota, and published with numerous extracts from the letters of Horrocks to Crabtree, and a sketch of the author’s life, in a volume entitled Jeremiae Horroccii opera posthuma (London, 1672). A memoir of his life by the Rev. Arundell Blount Whatton, prefixed to a translation of the Venus in sole visa, appeared at London in 1859.

For additional particulars, see J. E. Bailey’s Palatine Note-Book, ii. 253, iii. 17; Bailey’s “Writings of Horrocks and Crabtree” (from Notes and Queries, Dec. 2, 1882); Notes and Queries, 3rd series, vol. v., 5th series, vols. ii., iv.; Martin’s Biographia philosophica, p. 271 (1764); R. Brickel, Transits of Venus, 1639–1874 (Preston, 1874); Astronomical Register, xii. 293; Hevelii, Mercurius in sole visus, pp. 116–140; S. Rigaud’s Correspondence of Scientific Men; Th. Birch, History of the Royal Society, i. 386, 395, 470; Sir E. Sherburne’s Sphere of M. Manilius, p. 92 (1675); Sir J. A. Picton’s Memorials of Liverpool, ii. 561; M. Gregson’s Fragments relative to the Duchy of Lancaster, p. 166 (1817); Liverpool Repository, i. 570 (1826); ''Phil. Trans. Abridged'', ii. 12 (1809); C. Hutton’s ''Phil. and Math. Dictionary (1815); Penny Cyclopaedia'' (De Morgan); Nature, viii. 117, 137; J. B. J. Delambre, ''Hist. de'' l’astronomie moderne, ii. 495; ''Hist. de l’astronomie au XVIII&#8202;e siècle'', pp. 28, 61, 74; W. Whewell, ''Hist. of the Inductive Sciences'', i. 331; R. Grant, ''Hist. of Physical Astronomy'', pp. 420, 545; J. Mädler, Geschichte der Himmelskunde, i. 275; M. Marie, ''Hist. des Sciences'', iv. 168, vi. 90; J. C. Houzeau, ''Bibl. Astr.'' ii. 167.

 HORROCKS, JOHN (1768–1804), British cotton manufacturer, was born at Edgeworth, near Bolton, in 1768. His father was the owner of a small quarry, and John Horrocks spent his early days in dressing and polishing millstones. The Lancashire cotton industry was then in its infancy, but Horrocks was greatly impressed with its future possibilities, and he managed to obtain a few spinning-frames which he erected in a corner of his father’s offices. For a time he combined cotton-spinning on a very small scale with stone-working, but finally devoted himself entirely to cotton-spinning, working the frames with his own hands, and travelling through the Lancashire manufacturing districts to sell the yarn. His goods obtained a reputation for quality, and his customers increased so rapidly that in 1791 he removed to Preston, where he began to manufacture cotton shirtings and long-cloths in addition to spinning the cotton yarn. By taking full advantage of the machinery invented for manufacturing textiles, and by rigidly maintaining the quality of his goods, Horrocks rapidly developed his business, and with the aid of the capital of a local banker, whom he took into partnership, erected within a year of his arrival in Preston his first large mill, securing shortly afterwards from the East India Company a monopoly of the manufacture of cottons and muslins for the Indian market. The demand for Horrocks’s goods continued to increase, and to cope with the additional work he took first an elder brother and in 1801 a Mr Whitehead and a Mr Miller into partnership, the title of the firm being altered to Horrockses, Miller & Co. In 1802 he entered parliament as tory member for Preston. He died in London in 1804 of brain-fever resulting from over-work.  HORSE (a word common to Teutonic languages in such forms as hors, hros, ros; cf. the Ger. ross), a name properly restricted to the domesticated horse (Equus caballus) and its wild or half-wild representatives, but in a zoological sense used as a general term for all the members of the family Equidae.

The distinctive characteristics of the family, and its position in the zoological system, are given in the articles and . Here attention is concentrated on the leading features of the horse as contrasted with the other members of the same family, and subsequently on the anatomical structure of the former animal. The evolution of the existing representatives of the family from primitive extinct animals is summarized in the article.

Horse, Wild Horse, Pony.—The horse (Equus caballus) is distinguished from the others by the long hairs of the tail being more abundant and growing quite or nearly from the base as well as the end and sides, and also by possessing a small bare callosity on the inner side of the hind leg, just below the “hock” or heel joint, in addition to the one on the inner side of the fore-arm above the carpus or “knee,” common to all the genus. The mane is also longer and more flowing, and the ears are shorter, the limbs longer, and the head smaller.

Though existing horses are usually not marked in any definite manner, or only irregularly dappled, or spotted with light surrounded by a darker ring, many examples are met with showing a dark median dorsal streak like that found in all the other members of the genus, and even with dark stripes on the shoulders and legs.

Two distinct types of horse, in many instances largely modified by interbreeding, appear to exist. (1) The northern, or dun type, represented by the dun ponies of Norway (Equus caballus typicus), the closely allied Celtic pony (E. c. celticus) of Iceland, the