X THE STARRY HEAVENS 393 



that there is water in Mars, and the two poles 

 are tipped with white, as if capped by ice and 

 snow. It presents also a series of remarkable 

 parallel lines, the true nature of which is not 

 yet understood. 



THE MINOR PLANETS 



A glance at Figs. 51 and 52 will show that 

 the distances of the Planets from the Sun 

 follow a certain rule. 



If we take the numbers 0, 3, 6, 12, 24, 48, 

 96, each one (after the second) the double of 

 that preceding, and add four, we have the 

 series. 



4 7 10 16 28 52 100 



Now the distances of the Planets from the 

 Sun are as follow : — 



For this sequence, which was first noticed 

 by Bode, and is known as Bode's law, no 

 explanation can yet be given. It was of 

 course at once observed that between Mars 

 and Jupiter one place is vacant, and it has 



