TILE DRAINAGE. 25 



cease to pump when the flame goes out and ceases to take 

 and use what they pump. Observation attests the fact that 

 fine surface-tillage after showers helps to retain moisture, 

 and a full knowledge of the physical principles involved ex- 

 plains the reason. The sciolists, with their smattering of 

 science, are wrong as usual. 



A little knowledge is a dangerous thing; 

 Drink deep, or taste not the Pierian spring. 



I have tried to explain this point quite fully, partly on ac- 

 count of its bearing on the next two propositions. 



Tenth. Tile drainage on clayey soils helps the crops to resist 

 drouth better. It puts these soils in condition to receive this 

 surface tillage sooner after showers, for one thing, and hence 

 to retain moisture better. Again, it permits the crops to be 

 started earlier and pushed faster, and hence makes them 

 more likely to be out of the way of the July and August 

 drouths so common in this latitude. Still further, it puts 

 the whole soil more fully into that loose and spongy condi- 

 tion that enables it actually to hold more water and yet not be 

 too wet. A clayey soil not tile-drained tends constantly to 

 settle down and become too compact, especially if worked or 

 tramped when it is too damp ; and it almost always is too 

 damp in fall, winter, and spring. This reduces the size and 

 number of its capillaries, and hence they can not hold so 

 much ; just as a sponge with all its capillaries full loses half 

 its water if compressed to half its size. And this loose, 

 spongy, friable condition of the soil, that fits it to hold the 

 most water in its capillaries, is greatly increased by tile 

 drainage followed by proper tillage. When a clayey soil, not 

 tiled, is thoroughly soaked it becomes more or less puddled 

 and compacted, so that the proper air-spaces become smaller 

 and act as capillaries. It dries only by evaporation from the 

 top, as fast as the capillaries bring the moisture up. But 

 when it finally does get dry it is apt to bake into great dry 

 clods with little moisture, and little chance for roots to pen- 

 etrate and permeate it ; arid so a soil that has been ren- 



