MAttS. 503 



Beer, 24h. 37m. 23s. His sidereal revolution round the Sun, 

 occupies 1 year 321d. 17h. 30m. 41s. The inclination of 

 Mars' orbit towards the Earth's equator, is 24 44' 24*; his 

 mass, ^^-^jy; his density, in comparison to that of the 

 Earth, 0-958. The mass of Mars will be hereafter corrected 

 by means of the disturbances which he may experience from 

 his influence with the Comet of De Vico, in the same way 

 that the close approach of Encke's Comet was taken advantage 

 of to ascertain the mass of Mercury. 



The flattening of Mars, which (singularly enough) the 

 great Konigsberg astronomer permanently doubted, was first 

 recognized by William Herschel (1784). With regard to 

 the amount of the flattening, however, there was long consi- 

 derable uncertainty. It was stated by William Herschel to 

 be -j^; according to Arago's more accurate measurement, 14 

 with one of Rochon's prismatic telescopes, in the first instance 

 (before 1824), only in the proportion of 189 : 194, . e. g-g-.-g-, 

 by a subsequent measurement (1847), J T ; still Arago is 

 inclined to consider the flattening somewhat greater. 



If the study of the Moon's surface calls to mind many 

 geognostic relations of the surface of the Earth; so, on the 

 contrary, the analogies which Mars presents with the Earth, 

 are entirely of a meteorological nature. Besides the dark 

 spots, some of which are blackish, others, though in very 

 small numbers, yellowish-red, 66 and surrounded by the greenish 



Treatise, Kern, Diss. de Scintillatione Stellarum, Wittenb. 

 1686, 8, I find that the actual discoverers of the rotations 

 of Mars and Jupiter are stated to have been " Salvator Serra 

 and Father ^Egidius Franciscus de Cottignez, astronomers of 

 the Collegio Romano." 



u Laplace, Expos, du Syst. du Monde, p. 36. Schroter's 

 very imperfect measurement of the diameter of the planet 

 gave Mars a flattening of only -J^-. 



Beer and Madler, Beitraye, p. 111. 



