34 ELEMENTS OF GENERAL SCIENCE 



33. Seasonal changes of temperature. The change of tem- 

 perature that comes with the seasons is to many of us the 

 most notable and striking difference between the seasons. 

 Why should there be such a difference ? The sun still shines 

 as brightly as ever, and its heat has not decreased in the whiter. 

 We are no farther away from the sun. Why are not our homes 

 warmed as well by the suu in winter as in summer ? 



,r> in JSU.IUIAICI' 

 March 21 



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Sept. 22 

 FIG. 21. The earth's orbit 



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

 dates of the year 



All apparent changes in the sun's position are due to the 

 movement of the earth around the sun and to the inclina- 

 tion of the earth's axis (fig. 21). We often say that the sun 

 rises and sets, when we know that these appearances are 

 due to the motion of the earth. In the same way we say that 

 the sun is higher in the heavens in summer than in whiter, 

 meaning that we have changed our position so that the sun 

 appears higher. It is also noted that daylight lasts longer 

 in summer than in winter. 



