THE HEAVENS 



365 



quickening non-mathematical knowledge of an elementary 

 character. 



So vast are the values for time, space, and size in the celes- 

 tial sphere, values that approach the infinite in their magni- 



FIG. 1 1 8. Constellations of the northern heavens always above horizon in 

 most parts of the United States. 



tude, that the human mind must resort to comparisons 

 involving enormously large units in many cases. Only a few 

 of the more serviceable of these numbers need be remem- 

 bered, and these only as approximate values. The velocity 

 of light, 186,000 miles per second 1 , serves the astronomer as 

 1 The velocity of sound is only a little more than one-fifth mile (noo feet) 

 per second. 



