CHAPTER V 



THE SEASONS CLIMATE AND HEALTH 

 I. THE SUN THE CAUSE OF THE SEASONS 



307, The Sun's Altitude and Its Heating Effect. The height 

 of the sun above the horizon at noon is different for every dif- 

 ferent latitude upon any given day. It also is different for 

 any given latitude upon different days of the year. The 

 earth receives all its heat from the sun. We shall soon see that 

 the nearer the sun is to being at the zenith (the point directly 

 overhead), the greater is its heating power. Therefore, the 

 changing altitude of the sun is one of the principal causes of 

 seasons. 



Exercise 63. To Construct a Clinometer and to Measure the Altitude 



of the Sun 



(a) On a piece of cardboard about 20 in. square, mark out the 

 quarter of a circle as shown in Fig. 210. To do so, make a small loop 

 at the end of a piece of wrapping 

 twine. Slip a pencil point through 

 this loop. Place one finger tightly 

 upon the string so as to make 

 the radius exactly 20 in. Draw the 

 arc of the circle from to 90. 

 Next mark off the scale by dividing 

 the distance from to 90 into 

 eighteen equal parts. Each space 

 will then represent 5. If the 

 radius is exactly 20 in., the distance 

 from to 90 around the arc is % 

 of 2 X 20 X 3.14 in., or 31.4 in. 

 Each of the eighteen equal parts will 

 then be a trifle less than 1% in. 

 These 5 spaces may then easily be divided into five equal spaces, 

 thus marking off degrees. 



281 



FIG. 210. 



