THE MINOR PLANETS. 



149 



that we possess of the planet Venus, showed the existence of several mount- 

 ains on that planet, the height of some of which he estimated to amount to > 

 twenty-two miles. There were three which he estimated : the first at nineteen 

 miles, or five times the height of Chimborazo ; the second at eleven and a half 

 miles ; and the third at ten and three quarters miles. 



INFLUENCE OF THE SUN AT MERCURY AND VENUS. 



The distance of the earth from the sun being greater than that of Mercury 

 in the ratio of 100 to 39, or nearly 5 to 2, the apparent diameter of the sun as 

 seen from Mercury will be greater than as seen from the earth in the same 

 ratio. If E represent the apparent magnitude of the sun as seen from the 

 earth, M will represent it as seen from Mercury. 



The intensity of the sun's light being in the proportion of the area of its ap- t 

 parent disk, will be greater at Mercury than at the earth in the ratio of 25 to ' 

 > 4, or nearly as 6 to 1. If the heat depended solely on the sun's rays, it would < 



