Lesson iv.] MERCUHY. 17 



to treat upon them in so particular a manner, I 

 shall content myself with referring you to places 

 where you may find abundant information in these 

 respects. (See the books recommended towards 

 the end of these Lessons.) 



Those planets which move in orbits within that 

 of the earth, are called inferior, perhaps more 

 properly Interior planets : those whose orbits en- 

 close the earth's are called superior, or more pro- 

 perly exterior planets. 



Mercury is the smallest of the inferior planets, 

 and the nearest to the sun, about which he is car- 

 ried with a very rapid motion. Hence it was 

 that this planet was considered mythologically 

 as the messenger of the gods : he v was repre- 

 sented emblematically by the figure of a youth 

 with wings at his head and feet, and his cadu- 

 ceus entwined by winged serpents. The cha- 

 racter $ in present use for this planet i also de- 

 rived from the mythological description. Though 

 small, he has a bright appearance, with a light 

 tinct of blue : he never departs 28 from the sun, 

 and on that account is usually hid in the splen- 

 dour of that luminary. 



The mean distance of Mercury from the sun, 

 is to that of 'the earth from the sun, as 387 to 

 1000: hence his distance is about 37 millions of 

 miles. The sun's diameter will appear at Mer- 

 cury nearly three times as large as at the earth : 

 and the sun's light and heat received there, is, 

 as before observed, about seven times those at 

 the earth. 



The 



