WEATHER AND CLIMATE 153 



March 21 to September 22 the northern hemisphere 

 is inclined toward the sun. During that time the 

 region around the north pole receives light contin- 



June 21 



FIG. 57. Diagram of the path of the earth around the sun 

 showing the position of the earth with reference to the sun on 

 four dates. The dotted line represents an ellipse, and the earth 

 and sun are in the same plane. 



uously for some time. Throughout all the northern 

 hemisphere, during this period, the days are longer 

 than the nights. 



The rays are most nearly vertical in our latitude 

 on June 21, and our day is then the longest and our 

 night the shortest. From then on, the inclination of 

 the earth's axis toward the sun becomes less until 

 September 22, when it is at right angles to the sun 

 and the day and night are equal in length. 



Gradually the north pole becomes inclined away 

 from the sun, the rays from the sun become more and 

 more oblique in the northern hemisphere, the tempera- 

 ture becomes lower, and the nights become longer. 



