46 



Our Surroundings 



inside of each tube at the terminal, and will then rise in the 

 tubes. It will be found that twice as much gas forms in one tube 

 as in the other. These are the two gases of which water is com- 

 posed, one of which scientists have proved to be 

 oxygen and the other hydrogen. The larger 

 amount of gas is hydrogen. 



Distribution of Water. Water is widely dis- 

 tributed. Of the 197,000,000 square miles that 

 make up approximately the surface of the earth, 

 about 144,000,000 square miles, or nearly three- 

 I fourths of the earth's area, are covered by the 

 jJLl jlnJ\ oceans, lakes, rivers and small streams of water. 

 * >( I If* Water is a part of all living things and is neces- 

 / \ It I \ sar y to t h e j r growth. Many inorganic materials 

 absorb it, such as porous rock and sand. 



The water on the earth is constantly evaporat- 

 ing, that is, changing into water vapor. In this 

 form it rises into the atmosphere and forms clouds 

 and mists. These finally condense into the rain 

 which falls on the earth. This process is going 

 on all the time and greatly influences the weather 

 of every section. 



Water and Heat. It takes more heat to 

 change a given amount of water one degree in tem- 

 perature than any other of the common things we 

 know. The rocks and soil require a much less 

 amount of heat to change their temperature one 

 degree than does the same weight of water. 

 Knott Apparatus co. Experiment to Show Change in the Tem- 

 ELECTROLYSIS P^rature of Water. Place a given amount of 

 APPARATUS water, say one pound, in a tin dish. Warm this 

 An electric cur- wa ter to a rather high temperature but not to the 



rent breaks up the 



wa and iJydroge y rf en boiling point. After taking the temperature of 

 this hot water, add an equal amount of cold water 

 whose temperature is known. The temperature of the mixture 

 will be approximately the average, or half way between the two 

 temperatures taken. 



