EVAPORATION BOILING, TEMPERATURE, ETC. 9 



artificial light where gas or electricity is unobtainable. Gaso- 

 line lamps of many different kinds have been made and 

 in many homes gasoline is used both for lighting and cooking. 

 With this increase in its use people have discovered that gaso- 

 line is also one of man's most dangerous servants if not care- 

 fully and properly handled. Many accidents have resulted 

 from its use. Most people who use gasoline know that it is 

 more dangerous than is kerosene. But many people are using 

 gasoline every day who do not know just why it is dangerous, 

 what to do with it, or how to handle it to make it a safe and 

 obedient servant. 



We should like to study gasoline; we hope to learn its 

 nature and how to handle it. Before we can do so, however, 

 we must know the meaning of certain terms and how to 

 use them correctly. We must know where gasoline comes 

 from and its relation to kerosene. These topics will be studied 

 next. 



12. Evaporation. We are all aware that damp clothes 

 hung upon the line at any time except when it is raining 

 soon lose the water they contain and become dry. We wash 

 our porches and floors and soon they are dry. We place 

 a basin of water in an exposed place and the water soon 

 disappears. 



The explanation is that the water changes from a liquid to 

 a gas, or vapor, and escapes into the air. This process by which 

 water changes from its liquid form into a gas, or vapor, we call 



EVAPORATION. 



The washerwoman is also aware that on some days the clothes 

 will dry much more rapidly than on others. We know that 

 the freshly washed floors will dry more quickly if we open the 

 doors and windows or build a fire in the furnace or stove. 

 The farmer has learned to tell very accurately, by watch- 

 ing the weather, whether or not the fields and roads are drying 

 rapidly. The question naturally arises: What are the con- 

 ditions under which evaporation takes place most rapidly? 

 This question can best be answered by experiment. 



