WEATHER; WINDS AND STORMS; CLIMATE 117 



tically, that is, at right angles to the earth's surface. On 

 the same day at the arctic circle heat is received in slanting 

 lines, at about half of a right angle. The same amount of 

 heat spreads over a larger surface when it falls obliquely 

 than when it falls vertically. Therefore any given area at 

 the arctic circle receives less heat than an equal area at the 

 tropic of Cancer. 



The second condition affecting temperature is altitude, 

 or the elevation of a place above sea level. We use sea 

 level as a convenient uniform basis from which to reckon 

 altitude, even though the place considered may be thousands 

 of miles from the sea. / 



The farther one rises 

 above the earth, the less 

 heat is found. This 

 is because the earth 

 warms the air. A high 

 mountain, rising above 

 the great mass of the 

 earth, is surrounded by 

 cool layers of air. The 

 mountain receives less 

 heat and likewise gives 

 out less heat to the 

 surrounding air than 

 land on the lower levels 

 of the earth. 



The third condition 



c a o 



FIG. 56. VARIATIONS IN THE AMOUNT 

 OF HEAT AT DIFFERENT LATITUDES 



If each vertical line represents the same 

 number of rays of heat as each oblique line, 

 then the surface ab receives the same 

 amount of heat, as cb. 1. Compare the 

 amount of heat received on j of ab with 

 the heat on an equal surface of cb. 2. In 

 what month does Cuba receive vertical 

 rays? 3. Name some part of the world 

 upon which rays would fall obliquely (as 

 affecting the tempera- on cb) in the same month. 4. In which case 



ture of a place is near- would a sc * uare mile of the earth receive 



, , , , more heat? 



ness to a great body of 



water. The ocean, or any other large body of water, absorbs 

 more heat and warms more slowly than the land at the 

 same temperature. When the ocean, for instance, has 

 become warmed to 80 F., it has absorbed more heat than 



