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KEPLER SOT a port of delivery in 1854, and has an im- portant trade. The business of pork packing is carried on to some extent, and there are flouring mills, iron f ounderies, &c., three banks with an aggregate capital of $400,000, and a savings bank. The college of physicians and snrgeons, established in 1849, in 1872 had 10 professors and instructors and 105 students. The Keokuk library association possesses 7,000 volumes. The public schools, including a high school, are well organized and largely attended. There are two daily and three weekly (one German) newspapers, and 17 churches. KEPLER, Jolmiin. a German astronomer, born at Magstatt, near Weil, Wurtemberg, Dec. 27, 1571, died in Ratisbon, Nov. 15, 1630. He was a sickly child, and during his whole life suffered periodically from fevers and other ail- ments. His father, a man of noble origin and at one time a soldier in the Netherlands under the duke of Alva, having been reduced by the loss of his property to the condition of an inn- keeper, young Kepler was during a portion of his childhood employed by him in a menial ca- pacity. In 1586 he entered the monastic school of Maulbronn, whence he was transferred to the university of Tubingen, where in 1591 he took his degree of master. Subsequently he devoted himself to the study of astronomy under Mostlin, a disciple of Copernicus, and in 1594 was called to the professorship of math- ematics in the university of Gratz in Styria. Here in the same year appeared his first pub- lication, an almanac for 1595, followed in 1596 by his " Cosmographical Mystery," containing a fanciful theory regulating the order of the heavenly bodies. In 1597 he married a young widow named Barbara Muller von Mulech, and soon after, in consequence of domestic dissen- sions, and of religious troubles which threat- ened the safety of the Protestant professors in Gratz, of whom he was one, he accepted Tycho Brahe's invitation to go to Prague and assist him in the preparation of a new set of astronomical tables. The work was done by order of the emperor Rudolph II., who intended to substitute tables having his own name for those calculated on the Ptole- maic and Copernican systems. Tycho shortly afterward died, and Kepler succeeded him as principal mathematician. He was thenceforth constantly involved in pecuniary difficulties, in consequence of the inability or neglect of the emperor to pay him the full amount of his sal- ary. For this reason he was obliged to eke out a subsistence by casting nativities and wri- ting popular almanacs. In his " Principles of Astrology " (1602) he describes the power of certain harmonious configurations of suitable planets to control human impulses. In his day such a belief was regarded as in accordance with just conceptions of the attributes of the planets, and Kepler's most profitable employ- ment at this time was drawing the horoscopes of the princes. In his optical treatise, "A Supplement to Vitellio," published in 1604 at Prague, although unable to discover the pre- cise law of refraction, he was nevertheless singularly successful in his inquiries respect- ing vision, and in analyzing the structure of the eye. In this work he also described the mode of calculating eclipses which obtains at the present day. In his subsequent work on optics, entitled "Dioptrics" (Augsburg, 1611; reprinted in London, 1653), which, according to Sir David Brewster, " laid the foundation of the science," he explained the method of tra- cing the progress of rays through transparent bodies with convex and concave surfaces, and of determining the foci of lenses, and of the rel- ative positions of the images which they form and the objects from which the rays proceed. Hence he was led to describe the astronomical telescope, having two convex lenses, by which objects are seen inverted. These discoveries, however, are obscured by the greatness of those announced in his "New Astronomy, or Com- mentaries on the Motions of Mars " (Prague, 1609), which were founded on the astronomi- cal data prepared by Tycho. After many fruit- less attempts to represent the orbit of Mars by combinations of uniform circular motion (that is, by epicyclic curves), he discovered, by com- paring together seven oppositions of that plan- et, that its orbit is elliptical, whence he con- cluded that the orbit of each planet is an ellipse, with the sun placed in one of its foci. Having next ascertained the dimensions of the orbit of Mars, he found that the radius vector, or line joining the planet and the sun, described equal areas in equal times, and that the same was true of the other planets. These results constitute the first two of the three great laws of planetary motion known as Kepler's laws, the third of which was discovered nine years later. The labor and patience with which Kepler conducted these investigations will be best appreciated when it is considered that the calculations were made without the assist- ance of logarithms, which were a later inven- tion, and that each calculation of an opposi- tion of Mars, filling 10 folio pages, was repeat- ed 10 times, so that 7 oppositions produced a folio volume of 700 pages. In view of such difficulties, the remark of Prof. Playfair is par- ticularly pertinent, "that the discoveries of Kepler were secrets extorted from nature by the most profound and laborious research." Notwithstanding the reputation which these brilliant discoveries gained for him, his worldly circumstances showed no signs of improvement. Not only did his arrears of salary remain un- paid, hut the emperor Rudolph refused to allow him to accept the professorship of mathematics at Linz ; and to add to his embarrassments, his wife died and his children were attacked by the smallpox, which proved fatal to the eldest. At this time also Prague was occupied by Aus- trian troops, and the plague devastated the city. Upon the accession of the emperor Mat- thias, in 1612, he was allowed to accept the professorship at Linz, and three years later ha