58 DOMESTIC WATER SUPPLIES FOR THE FARM 



in the surrounding materials, will pass outward through any leak 

 that may develop rather than admit the water of lower head to 

 the well. Suction, such as is developed in the Richards apparatus 

 in laboratories, which might be conceived of as drawing in outside 

 water through openings in the casings, can not take place with the 

 relatively low velocities of the water in the ordinary artesian 

 wells. Even in a well in which the water has a very high velocity, 

 the suction is so slight in proportion to the immense volume dis- 

 charged that it may usually be neglected. 



Because of the fact that there is little likelihood of pollution 

 of a flowing well, the exact situation is, from the sanitary stand- 

 point, of little consequence, and the well may generally be 

 located at the point that is most convenient. Since flows are 

 dependent upon the head of the confined water, the pressure of 

 which is generally very moderate, it follows that the well should 

 be located at the lowest point possible. A difference of altitude 

 of a few feet, or even a few inches, may decide whether or not a 

 flow will be secured. 



Relation of Depth to Flows. - - There is a general belief that 

 the head of underground waters, and therefore the probability of 



FIG. 32. Artesian system showing progressively higher outcrop of deeper beds. 



securing flows, increases with depth. In many instances, as 

 under the conditions shown in Figure 32, there is some foundation 

 for this assumption, since the deeper beds not infrequently out- 



FIG. 33. Artesian system showing progressively lower outcrop of deeper beds. 



crop at successively higher lands than the shallower beds. In 

 other instances the belief is not only without foundation, but the 

 reverse conditions exist, as shown by Figure 33. 



