TEMPERATURE CHANGES AND THE SEASONS 17 



We all know that it does make a difference, for we readily 

 feel that the heat which we receive at noon in the winter and 

 at noon in the summer are not the same. Also, we notice the 

 same thing when we compare the morning or evening effect 

 of the sun with the effect at noon. 



The reason for this difference in the effect of the sun's rays 

 is not difficult to understand if we make use of a simple ex- 

 periment. Suppose in the morning, when the sun is not very 



March 21 



June 22 -5(<S)5- Dec. 22 



Sept. 22 

 FIG. 14. The earth's orbit 



A diagram showing the position of the earth with reference to the sun on four 

 dates of the year 



high, we hold a piece of paper with a large hole in it squarely 

 facing the sun and notice the size of the spot of light on the 

 ground. At noon we do the same. It will be seen that the 

 spot of light observed in the morning experiment was larger ; 

 that is, in the morning, when the rays of the sun were more 

 aslant than at noon, the rays of light and heat that came 

 through the hole covered a larger space on the surface of the 

 earth than at noon, when the rays were more nearly at right 

 angles with the earth's surface (fig. 15). The light and heat 



