490 AGRICULTURAL ENGINEERING 



where the water is likely to contain sand, as the seat of the 

 ball valve is usually quite narrow and the sand is not given 

 an opportunity to lodge upon it. 



The Stock. The part of the pump visible above the plat- 

 form is known as the stock, and is made in a variety of styles. 

 The simplest form is the lift pump, which, as a hand pump, 

 was formerly made with wooden stocks, but now cast-iron is 

 generally used. The next simplest is the force pump, made 

 after the plan of the common lift pump, with provision to pre- 

 vent leakage about the pump rod. 



Where the water is to be pumped into a storage tank and 

 the pump is in a more or less exposed location, a three-way 

 pump may be used. It provides a valve that enables the 

 water to be pumped out of the spout, or delivered through an 

 underground pipe to the storage tank, or drawn from the tank 

 through the spout. 



In cold climates a pump should be protected against freez- 

 ing by surrounding the valves with a frost-proof well pit and 

 providing for the drainage of the pump stock. If a com- 

 pressed air system of water storage is installed, a special 

 pump must be provided which will pump a little air with the 

 water; or a separate air pump must be used. 



QUESTIONS 



1. Is the pumping of water by hand ever economical? 



2. What are the principal sources of power for pumping water? 



3. Discuss the relative merits of the gasoline engine, the windmill, 

 and the hot-air engine, for pumping water. 



4. Describe the difference between a lift pump and a force pump. 



5. What are the relative merits of the different kinds of pump 

 cylinders? Pump valves? 



6. Describe the three-way pump and its use. 



7. How should a pump be protected from freezing? 



