SUN'S RAYS. 293 



Q. Why is there always SOME motion in the 

 air ? 



A. As the earth is always turning 

 round, the vertical rays of the sun are 

 always varying. 



Q. What do you mean by "the VERTICAL 

 BAYS of the SUN ?" 



A. The rays made at noon-day : when 

 the sun is in a direct line above any place, 

 his rays are said to be "vertical" to that 

 place. 



Q. How are the VERTICAL rays of the sun 

 always VARYING ? 



A. Suppose the brass meridian of a 

 globe to represent the vertical rays of the 

 sun; as you turn the globe round, 

 different parts of it will pass under the 

 brass rim, in constant succession. 



Q. And is it NOON-DAY to the place over which 

 the SUN is VERTICAL ? 



A. Yes ;, as each place passes under 

 the brass meridian, it is noon-day to one 

 half, and mid-night to the other. 



Q,. Show how this ROTATION of the earth 

 affects the AIR. 



A. If we suppose the brass meridian 



ca 3 



