AIR TEMPERATURES AND THE SEASONS 37 



is not the same at all places. It is least at the equator and 

 greatest at the poles. At intermediate places the difference 

 corresponds to the distance from the equator. In the central 

 part of the United States (central from north to south) the 

 longest daylight, in the latter part of June, is about fifteen 

 hours, and the shortest, in the latter part of December, is 

 about nine and one half hours (fig. 23). 



The angle of the sun's rays and the number of hours 

 during which it shines upon us work together to make the 

 earth and the air warmer in summer than in winter. From 

 the Government Weather Bureau reports and from other 

 publications it is possible to find out the length of the day on 

 the first of each month and to prepare a chart which shows 

 the change in the length of the day during the year. 



36. Daylight saving. During the past few years an active 

 daylight-saving campaign has been developed. It is argued 

 that the ordinary hours for professional and industrial occu- 

 pations should be changed at different times of the year so 

 as to utilize natural light more fully and to avoid the long 

 unused-light period during summer when business hours 

 begin at 8, 8.30, or 9 A.M. and daylight begins at from 4 to 

 5 A.M. The new legislation is not designed necessarily to 

 lengthen the number of hours during which any one person 

 works, but rather to leave more free time for leisure occu- 

 pations. The opponents of the plan claim that no material 

 advantage results from the legislation upon this question ; 

 that there is ample light during spring, summer, and autumn 

 for a full day's work ; that leisure hours can be arranged 

 by those who desire them and can use them ; that there is 

 an irreducible amount of time needed for sleep, meals, and 

 recreation upon which the plan may encroach. 



