128 



INTRODUCTION TO GENERAL SCIENCE 



through it quite readily; nevertheless, some of the energy is 

 stopped, and where any kind of energy is stopped, heat is 

 always produced. This is the direct method of heating. 



When the sunlight strikes the earth, which is opaque, all 

 of the energy is stopped, and it is all turned into heat. Thus 

 the surface of .the earth becomes very warm. It warms the 

 air above it by conduction; this warmed air expands and is 

 pushed up by the colder air on all sides, and we say that air 

 is becoming warm by convection. Most of the heat of the air 

 is obtained in this indirect way. The earth is prevented, to a 

 certain extent, from becoming too hot by the cold air coming 

 in on all sides. 



References : 



1. 1103:182-183. 



2. 1304:238-239. 



3. 1601:3-4. 



4. 1803:220-221. 



5. 1803:223-224. 

 a. 1102:77. 



6. 1301:64-66. 



c. 1303:28-29. 



d. 1306:68-69. 



e. 1307:216-217. 

 /. 1310:334-336. 



The Heat in the Air. 



The Warming of the Air. 



Air Warmed by Sunshine. 



Warming of the Air and Ocean. 



Warming and Ventilation of Houses. 



The Motion Conditions of General Con- 

 vection. 



Effect of Heat on Air. 



Temperature of the Atmosphere. 



General Circulation of the Atmosphere Due 

 to Heat. 



Effects of Temperature on the Air. 



The Heating of the Atmosphere. 



94. WINDS 



Air in motion is wind. The air has a definite weight, which 

 produces the pressure of about fourteen and seven tenths 

 pounds per square inch, or about one ton per square foot, on 

 the entire surface of the earth. If the air ill one section is 



