36 JUPITER. [Lesson viu. 



wisely ordered ! for if the axis of this planet were 

 inclined any considerable number of degrees, so 

 many degrees round each pole would be almost six 

 years together in darkness. And as each degree 

 of a great circle on this planet, contains more than 

 700 miles; it is natural to conceive, that vast 

 tracts of land would be rendered uninhabitable, by 

 any considerable inclination of his axis. 



Jupiter, when viewed through a telescope, is 

 found to be surrounded by faint substances called 

 zones or belts. These belts are generally parallel 

 to its equator, which is very nearly parallel to the 

 ecliptic : they are subject to great variations, both 

 in respect to their number and figure: sometimes 

 eight have been seen at once, and sometimes only 

 one; sometimes they continue for three months 

 without any variation, and sometimes a new belt 

 has been formed in less than two hours. From 

 their being subject to such changes, it is very pro- 

 bable that they do not adhere to the body of Jupi- 

 ter, but exist in his atmosphere. Dr. Smith in his 

 Optics has given a curious, account of these bells; 

 and the greater part of the writers on astronomy 

 have presented descriptions of them. 



This planet, when viewed by the unassisted eye, 

 is remarkable for its pure white brightness; indeed 

 it is the brightest of all the planets, except some- 

 times Venus. This may appear singular when we 

 remember his great distance from the sun ; but 

 when we also consider his enormous bulk, the 

 wonder will cease. 



In the year 1610, Galileo discovered that Ju- 

 piter 



