72 BULLETIlSr 414, U. S. DEPAETMENT OP AGEICULTURE. 



scrupulously clean and free from filth of all kinds; (3) by constructing 

 the well itself in such manner as to prevent the entrance of polluting 

 matter. 



CONSTRUCTION OF WELLS. 



A shallow dug well under ordinary conditions should be lined with 

 some impervious material, such as concrete, brick or stone laid in 

 cement and pointed on the inside, or terra cotta sewer pipe cemented 

 at the joints; and this casing should be built as deep into the well as 

 practicable. In temporary camps, those in charge usually feel that 

 they can afford neither the time nor the material to construct casings 

 of any of the materials mentioned above, and rather favor the use of 

 wooden casings, used more for the purpose of preventing the sides 

 from caving than for keeping out surface pollution. In such cases, 

 all precautions as to the location of the well in relation to privies, 

 stables, and other sources of pollution become more vital than ever. 

 The space between the wooden casing and the earth should be very 

 carefully fiUed with sand or earth tamped as the casing is put in. 

 Sand is preferable because it is of value in aiding in the purification of 

 any surface water which may percolate through it; clay is somewhat 

 unsafe for the purpose, as some kinds of clay shrink and crack on 

 drying, and if this occurs, polluted water may find its way through the 

 cracks to the weU. Wooden casings, however, should be used only in 

 temporary camps, if at all. When used for long periods they decay 

 and impart an unpleasant taste to the water, and in the end may be 

 more expensive than one of the more durable kinds of casing. 



Driven wells are constructed by attaching a perforated point 

 to the end of a pipe from IJ to 4 inches in diameter, and driving the 

 pipe into the ground until water is reached. The water enters the 

 pipe through the perforations in the point, which are small enough to 

 keep out sand and gravel. 



The upper end of the pipe usually is attached directly to a pump 

 by which the water is raised. The vibration of the pipe, caused by the 

 pump, often loosens the earth about the tubing so that a channel is 

 formed through which surface water may enter the well; and the 

 joints in the pipe also have been known to loosen so as to permit the 

 entrance of surface water. To obviate the former trouble it is neces- 

 sary to provide a heavy timber or concrete platform to which the 

 frame of the pump may be fastened tightly. The pipe should be 

 inspected occasionally with a view to the removal of all leaky and 

 rusted sections. Waste water from the pump should be carried by a 

 pipe or spout to a considerable distance from the well, and dirty 

 water never should be used in priming. 



When a distance of 100 feet or more is traversed before water 

 is struck, the term " deep well" is commonly appMed. If, after water 



