XXI.j 



THE SUN. 



363 



fectly pure. If the spots are watched day after day, they 

 may be seen to march slowly across the disc, all moving in 

 the same direction from the eastern edge or limb, towards 

 the western side, and completing the march in about fourteen 



o 



EARTH 



Fig. ii3. — Ccmparative sizes of the sun and the earth. In tire course of engrav- 

 ing the circle representing the earth has become a little too large. In order 

 to represent the true dir.tance of the eartli from the sun, the two figures ought to 

 be abjut twenty -seven feet apart. 



days. A fortnight afterwards, some of the very same spots 

 which were lost may possibly reappear on the eastern edge, 

 though altered in shape. This regular movement of the 

 spots teaches us that the sun rotates on its axis, and thus 



