ON THE LAWS OF GRAVITATION. 409 



i 



LECT. XLIL ADDITIONAL AUTHORITIES. 



Descriptions. Sun. Hausen, 4to, Leipz. 1726. Schroter, 4to, Erfurt. 1789. 

 Woodward, Washington, 1801. 



JL*",o. Hevelii Selenographia, fol. Dantz. 1667. Cassini, Carte de la Lune. 



Mylivis, Uber die Atmosphare des Mondes, 4to, 1746. Mayer's Cosmographische 



% J/achrichten. 1748, p. 379. Von dem Mondkiigeln, 4to, Numb. 1750. Schroter's 



rSelenotopographische Fragmenten, 2 vols. 4to, Gott. 1791. Beer's Map of the 



Moon. 



V Orbits. See Lect. 43 ; also Primary Planets. Halley's Mode of determining the 

 Orwts, Ph. Tr. 1676, p. 683. Huygenii Cosmotheros, 4to, Hag. 1698. Varignon, 

 HisA et Mem. 1 700, p. 224, H. 78. Cacciatore, Sull' Origine della Sistema Solare, 

 Palermo, 1826. 



'/' Kepler's Prob. Keill, Ph. Tr. 1713, p. 1 ; Machin, ibid. 1783, p. 205. 

 Stewart, Ed. Ess. ii. 105. Lagrange, Hist, et Mem. de Berlin, 1764, p. 204. 

 Sejour, Hist, et Mem. 1790, p. 401. Ivory, Ed. Tr. v. 203. Brinkley, Ir. Tr. vi. 

 349 ; ix. 83. 



Secondary Planets. Clairaut on the Moon's Orbit, Hist, et Mem. 1743, p. 17, 

 H. 123 ; 1748, p. 421. Theorie de laLune, 4to,Petersb. 1752. Stewart, The Dis- 

 tance of the Sun deduced by Theory, Ed. 1763. Mayer, Theoria Lunse, 4to, Lond. 

 1767. Euler, do. Laplace, Hist, et Mem. 1784, p. 1 ; 1785, Errata; 1786, 

 p. 235 ; 1788, p. 249 ; 1789, p. 1, 237. 



Comets. Bartholinus de Cometis, 4to, Copen. 1665. Lubinietz, Theatrum 

 Cometicum,fol. Amst. 1668. Hevelius, Cometographia, fol. Gedani, 1668. Cassini, 

 Sur la Comete de 1680, 4to, Paris, 1681. Bernoulli, Conamen Novi Systematis 

 Cometarum, 12mo, Amst. 1682. Whiston's Praelectiones, 1710. Lemonnier, La 

 Theorie des Cometes, Paris, 1743. Heinsius, Ueber den Comet, von 1743, 4to, 

 Petersb. 1744. Loys des Cheseaux, do. Lausanne, 1744. Martin's Theory of Comets, 

 4to, 1757. Lambert, Insigniores Orbitae Cometarum Proprietates, Augsb. 1761. 

 Wideburg, Ueber den Com. Jena, 1769. Lambert on the Apparent Orbit of 

 Comets, Hist, et Mem. de Berlin, 1771, p. 352. Oliver on Comets, Salem, 1772. 

 Laplace, Mem. des Sav. Etr. 1773, p. 503. Dionis de Sejour, Hist, et Mem. 1774, 

 H. 78; Essai, Paris, 1775. Condorcet, Dissertation, 4to, Utr. 1780. Pingre", 

 Cometographie, 2 vols. Paris, 1783. Piazzi, Della Cometa del 1811, 4to, Palermo, 

 1812. Englefield on Comets, 4to, 1793. Legendre, Sur les Orbites des Cometes, 

 4to, Paris, 1806 ; Supplement, 4to, 1820. Schroter, Ueber den Grossen Com. von 

 1811, Gott. 1815. Cacciatore, Delia Com. di 1819, Palermo, 1819. Lubbock, On 

 the Orbit of a Comet, Mem. of the Ast. Soc. 1829. Encke, Ueber die Nachste 

 Wiederker des Cometen von Ponsin Jahr. 1832, Altona, 1831. Airy on Encke's 

 Comet, Camb. 1832. Littrow on do. Wien, 1832. Stratford, Ephemeris of Halley's 

 Comet, 1835. Arago, Des Cometes, 18mo, Par. 1834. Virlet, do. 18mo, Avesnes, 

 1835. Mime on Comets, Ed. 



LECTURE XLIII. 



ON THE LAWS OF GRAVITATION. 



IT was first systematically demonstrated by Sir Isaac Newton, that all 

 the motions of the heavenly bodies, which have been described, may be 

 deduced from the effects of the same force of gravitation which causes a 

 heavy body to fall to the earth ; he has shewn that in consequence of this 

 universal property of matter, all bodies attract each other with forces de- 

 creasing as the squares of the distances increase ; and of later years the 

 same theory has been still more accurately applied to the most complicated 



