192 



LAND DRAINAGE 



253. Springy low flat areas. The springs in low flat 

 areas occur because the underground water, moving from 

 other higher areas, cannot escape downward sufficiently 

 rapidly because of underlying clay, hard-pan, or rock. 



FIG. 84. To show how a springy condition might be produced. The 

 clay or hard-pan / would divert the water sinking through the soil 

 S, and cause it to saturate and rise through the low lying soil (ab). 

 See paragraph 253. 



The water, therefore, comes to the surface as springs. 

 (See Fig. 84.) Sometimes this underground water ap- 

 proaches between two impervious layers as is illustrated 

 in Fig. 85. Such a condition as this was discovered, to 



FIG. 85. To illustrate the second condition mentioned in paragraph 

 253. S, any fairly open soil. 7, /, clay or hard-pan. G, a sand or 

 gravel layer filled with water gathered at some higher point. This 

 water is under pressure, and, therefore, rises through any opening 

 that may occur in the upper layer of clay or hard-pan. 



exist over an extended area in England, and led to a very 

 interesting and successful line of tile drainage in that 

 country as early as the year 1764. 



A line or system of tile, properly placed, intercepts and 

 carries off the water which otherwise would rise to the 

 surface and keep the soil wet and cold. The amount of 



