314 



HISTORY OF ASTKONOMY. 



totam astronoiniam rcformundam," since lie derived 

 from it the elliptical forms of tin- orliits of the |>lunrts 

 (differing, however, but little from the circles of 

 Copernicus), the sun being situated in one of tin- foci 

 of the ellipse. Advancing in his glorious course, 

 Kepler, moreover, demonstrated that, in each ellipti- 

 cal revolution of the planets around the sun, ;m ima- 

 ginary straight line, drawn from the latter to the 

 former (the radius vector), always describes equal 

 areas in equal times ; and, lastly, that, in the revo- 

 lutions of the planets and satellites, the squares of the 

 times of revolution are as the cubes of the mean dis- 

 tances from the larger body. These three important 

 truths are comprehended under the name of Kepler's 

 taws. About the same time, Galileo (q. v.), who died 

 in lo I'.', accomplished another step towards the more 

 accurate investigation of celestial mechanics, by his 

 discovery of the laws of the descent of heavy bodies ; 

 and although the Catholic churcli compelled this 

 philosopher to abjure as heretical the doctrine which 

 lie h;ul publicly promulgated respecting the motion 

 of the earth, to which he had been led oy his obser- 

 vaiions of the other celestial motions, made by means 

 of the telescope, then first invented, this attempt to 

 oliruct the march of intellectual improvement only 

 served to show the impotency of such persecutions.* 

 In the first ten years of the 17th century, there ap- 

 peared, in Dantzic, Hevelius, who was distinguished 

 for his observations of Mars ; in France, Cassini, 

 whose exertions in most of the branches of astronomy 

 were highly successful and who transmitted his in- 

 dustry and his energy to a son, grandson, and great- 

 grandson ; and in Holland, Huygens, the famous 

 inventor of the pendulum, and the precursor of the 

 immortal Newton, in his investigations respecting 

 celestial mechanics. Newton himself (q. v.), born in 

 1G4'2, was engaged, till a short time before his death, 

 1727, in producing an entire revolution in physical i 

 astronomy (see the preceding article), while, by his 

 Principia Mathematica Philosophies Nalitralis, he be- 

 came the lawgiver of celestial mechanics, as Kepler 

 liad been of theoretical astronomy, by means of his 

 Astronomia. Descartes had sought the cause of the 

 motion of the planets around the sun, and of the 

 satellites around the planets, in the rotatory motion 

 of a subtile matter. Newton felt the defects of this 

 hypothesis, and proved, with the superiority of true 

 genius, that the elliptical motion of the planets was 

 caused by the combined action of the attractive power 

 exerting a force in the inverse ratio of the squares 

 of the distances, and of an impulse originally com- 

 municated to the planets, which impulse, as may be 

 demonstrated, continues for ever in empty space. 

 With Newton the laws of the heavenly bodies' were 

 completed, and he and Kepler have left to later 

 times merely the developement of the truths which 



Sumtifi'iM Rudolph i II., Romanorum Imperatorit, etc., 

 i '--(/(/it Annorum pertinaci Studio etaborata, Pragte, u 

 'S. C. M. Mat'irmatico Joanne Keplero (1609, fol.). 



These persecutions have, nevertheless, been very 

 recently repeated, and the public papers have related the 

 following anecdote : About the beginning of the year 1820, 

 the professor of astronomy at the academy delta sapienza at 

 Rome, signer Settele, submitted the manuscript of his astro- 

 nomical lectures to the appointed authorities, soliciting per- 

 mission to print them. This was refused, " because he de- 

 fended the motion of the earth around the sun" a doctrine 

 condemned by the Roman court, as contrary to the Bible, 

 and which had already involved the immortal Galileo in 

 the disgrace of recantation. Not discouraged by this, 

 Settele applied to the inquisition, with the request that it 

 would give an explanation of its own, adapted to the pre- 

 sent state of science. The inquisition was silenced; per- 

 mission was granted to print the book; but Settele was 

 ordered .to add in a note, " in conformity with truth," that 

 the persecutions which Galileo had suffered were to be im- 

 puted not so much to his system as to the improper lan- 

 guage uaed by him. This, however U notoriously false. 



they established. By the application of their princi- 

 ples, several succeeding astronomers have gained a 

 high reputation ; e. g., Ilalley, by his theory of 

 comets ; Bouguer and Maupertuis, by their exertions 

 to determine the form of the earth; their country man 

 de la faille, by improving the doctrine of refraction ; 

 the great German astronomer, Tobias Mayer, by his 

 lunar tables; Bradley, by the discovery of the aber- 

 ration of light ; also de 1'1-le, Lambert, Kuhr, and 

 others, (q. v.) In more recent times, Laplace, by 

 his Mecanique Celeste, and Gauss, by his Theoria 

 Motus Corporum Calestium, have completed the 

 structure of Newton ; while Zach, Lalande, Maske 

 lyne, Bessel, Olbers, Piazzi, Eucke, Delamtuv, Biot, 

 Arago, Mechain, Herschel, &c., have enlarged, on 

 all sides, the territory of the science. Thus Iler- 

 schel's discovery of the planet Uranus and its mooas, 

 in 1781 ; Schroter's efforts to obtain a knowledge, of 

 the surface of our moon, and of Venus; Piazxi's dis- 

 covery of Ceres, in 1801 ; Olbers' discovery of Pallas, 

 in 1803, and of Vesta, in 1807 ; Harding's discovery 

 of Juno, in 1804; Olbers' and Encke's computation 

 of the orbits of two comets ; the recent measurements 

 of a degree in France, England, Germany, Sweden ; 

 the perfection which has been given to astronomical 

 instruments, by Ramsden, Troughton, Reichenbach, 

 &c., are well known ; and the combined industry 

 of so many living astronomers allows us to hope 

 for no less splendid results in the advancing im- 

 provement of astronomy. On the advantages of this 

 science, it can scarcely be necessary to dwell. " It 

 need but be mentioned," says Gehler, " to excite 

 emotions of grandeur ; and the idea which it gives 

 us of the immensity of the universe, itnd the power, 

 wisdom, and goodness of its almighty Author, must 

 inspire men of the coldest feelings with sentiments 

 of admiration. It is not necessary for us to point out 

 the benefits which accrue from it to the human race, 

 by enabling them to divide and observe the flight of 

 time ; its use in navigation, the determination of the 

 situation of places on the earth, &c." By the aid 

 which it affords to navigation, it exercises no small 

 influence in the general improvement of the human 

 condition. This science, moreover, unites the strict- 

 ness of mathematical reasoning with an exalted feel- 

 ing for the sublime and beautiful, and fills the mind 

 both with confidence in itself, from its ability to cal- 

 culate with certainty the career of distant worlds, 

 and with a becoming humility in reflecting how small 

 a part of the universe is our earth, and how brief its 

 known duration, compared with the immense periods 

 which enter into the calculations of astronomy. 

 Young says, 



An undevout astronomer is mad. 



There have been, however, several astronomers who 

 believed in no God ; being led, by the contemplation 

 of the necessary laws of the heavenly bodies, to the 

 belief in a general, universal necessity. Of the nu- 

 merous works on astronomy, we shall only mention 

 here the latest and most important manuals and ele- 

 mentary works: Astronomic par de Lalande, 3d ed., 

 Paris, 1792, 3 vols 4to. (there is an abridgment of 

 it Abrege d 'Astronomic par de Lalande, Paris, 

 1795) ; Astronomic Theorique et Pratique, par De- 

 lambre, Paris, 1814, 3 vols. 4to a work important 

 for professional astronomers ; Schubert's Theoretical 

 Astronomy, Petersburg, 1798, 3 vols. 4to, and a new 

 French edition of the same work, 1822 ; Biot's Traite 

 Elementaire d? Astronomic Physique, 2d ed., Paris, 

 1810, 3 vols. ; Laplace's Exposition du Systeme dn 

 Monde, 5th ed., Paris, 1824 (a general exposition of 

 the results developed in the large work, Mecanique 

 ('{lest?); Bode's Illustrations of Astronomy (which 

 is confined to the less difficult propositions of geome- 



