THE MINOR PLANETS. 



155 



covered, even by powerful telescopes, especially if it did not recede far from 

 the disk of the planet. 



APPEARANCE OF THE SUN AT MARS. 

 M 



The distance of Mars from the sun being greater than that of the earth in 

 the proportion of three to two, it follows that the apparent magnitude of the sun 

 to the inhabitants of Mars will be less than to the inhabitants of the earth in 

 the same proportion. In the annexed diagram, if E represents the appearance 

 of the sun to the earth, M will represent its appearance at Mars. 



The light which it affords will be in the same proportion as its apparent 

 magnitude ; and as the superficial magnitude of the disk will be about half 

 that which it presents to the earth, it follows that the intensity of the sun's 

 light at Mars will be less in the same proportion. But, for the reasons which 

 have been elsewhere stated, no safe inference can be made respecting the 

 effect of the sun on the temperature of the planets. 



The close analogy in which this planet stands to the earth will be apparent ( 



