CONTEXTS vii 



PAGE 



CHAPTER XI. WATER PRESSURE 118 



Importance of water. The siphon. The lift pump. Why the water 

 rises in the pump. The problems of water pressure. Pressure on 

 horizontal surfaces in general. Pressure on the sides of a tank. 

 Upward pressure in a liquid. Relation to size of a tank. Effect of 

 the shape of a tank. Pressure in other liquids. Calculation of 

 fluid pressure. Transmission of pressure in liquids. The principle 

 of the hydraulic press. Air pressure. Pressure in other fluids. 

 Dams. Buoyancy. Floating objects. Submarines and balloons. 

 Densities. 



CHAPTER XII. CLIMATIC INFLUENCES OF BODIES OF 

 WATER 130 



Importance of lakes and oceans. The Great Lakes. The lakes and 

 summer temperatures. The lake breeze. Cause of the lake breeze. 

 Causes of unequal heating of land and water. Cooling of land and 

 water. Effects of Lake Michigan on temperature. Reason for 

 difference between east and west shores. Some general conclu- 

 sions. Some effects of lake climate. 



CHAPTER XIII. COMMERCIAL RELATIONS: THE GREAT 

 LAKES 147 



Commercial importance of the Great Lakes. Advantages of water 

 transportation. Origin of lake cities : Chicago as a type. Exten- 

 sion and improvement of waterways. The railroads. Harbors. 

 Lights, buoys, and life-saving stations. Other ports. 



CHAPTER XIV. WATER SUPPLY AND SEWAGE DISPOSAL 154 



Sources of water supply. Importance of pure water. Kinds of 

 impurities. Sources of bacteria in lakes and rivers. Methods of 

 securing pure water. The problem of sewage disposal. Sewers. 

 A problem in sewage disposal. The sanitary canal. Sewage treat- 

 ment and disposal. Rural water supplies. Disposal of wastes in 

 rural districts. 



PAET III. WORK AND ENERGY 



CHAPTER XV. WORK BY RUNNING WATER . 165 



The power of running water. Work done by Niagara Falls. Utili- 

 zation of running water. Undershot water wheels. Overshot water 

 wheels. Turbines. 



