kARS, VESTA, JUNO, AND PALLAS. Ill 



LESSON 50. 



^ Mars, Vesta, Juno, Pallas, and Ceres. 



' JB Eccen'tric, deviating from the centre. 

 ' Eccentri^'ity, the distance between the centre of an ellipse and 

 the focus. 



Mars, the first of the exterior planets, is distinguished 

 from the rest by the redness of its colour, which has been 

 attributed to the density of his atmosphere. He revolves 

 round the sun in about tvv^o years, at the mean distance of 

 one hundred and forty-four millions of miles, and turns on 

 his axis in a little less than twenty-five Piours. The time of 

 his diurnal rotation was discovered by means of a large spot 

 seen on his surface, when in that part of his orbit which is 

 opposite to the sun and the earth. The telescopic appear- 

 ance of Mars is exceedingly variable ; but the predommant 

 brightness of his polar regions, leads to the supposition, that, 

 like those of the earth, they are covered with perpetual snow. 

 The proportion of ^sht and heat, received at Mars from 

 the sun, is less than'tDifi half of that enjoyed by the earth. 



The planet next to Mars in the solar system is Vesta. It 

 shines with a pure and white light, and is visible in a clear 

 evening without the aid of a telescope. ' It revolves round 

 the sun, in about three years and eight months, at the mean 

 distance of two hundred and twenty-three millions of miles. 

 Vesta was first discovered by Dr. Oibers, of Bremen, in 

 Lower Saxony, March 29, 1807. 



Juno was discovered by Mr. Harding, near Bremen, Sep- 

 tember 1, 1804. It completes its revolution in about four 

 years and four months, at a mean distance from the sun of 

 about two hundred and fifty-three millions of miles. It is 

 distinguished from all the other planets by the great eccen- 

 tricity .of its orbit ; and the effect of this is such that it 

 passes over one half of its orbit in half the time that it em- 

 ploys in describing the other half. From the same cause its 

 greatest distance from the sun is double the least distance, 

 the difference between the two distances being about one 

 hundred and twenty-seven millions of miles. 



Pallas was discovered by Dr. Oibers, March 28, 1802. It 

 completes its revolution in about four years and seven months, 

 and its orbit is nearly as eccentric as that of Juno. Its mean 



