26 TILE DRAINAGE. 



dered light, porous, and spongy., by tiling and proper tillage, 

 really has more water in it all summer that is available for 

 plant-growth ; that is, more in its proper capillaries to start 

 with, and with its air-spaces open. It also wastes less of its 

 moisture by evaporation, for reasons already given, and has 

 its pores open for the quick reception of any sudden showers, 

 thus preventing surface loss from the suddenness and rapid- 

 ity of the rainfall. 



Eleventh. Tile drainage often, though not always, dimin- 

 ishes the suddenness and violence of floods. On this point I 

 have carefully watched the behavior of my own tile-drained 

 land and of adjacent land not drained, and hence have facts 

 as well as theory to offer. I have often noticed this before, 

 but more carefully than ever this last winter of 1890-91. 

 The drained land had its air-spaces open all last winter, and 

 the ground thawed out almost at the beginning of each 

 thaw, and especially of each rain. The rain, descending 

 through these air-spaces, not only thawed the entire ground 

 sooner than if they had been frozen full of hydrostatic water, 

 but at once, often within an hour, set all the tile drains at 

 work. Tne rain as it fell was received into 30 inches deep of 

 porous, spongy soil, and gradually under hydrostatic pressure 

 (acting slowly through the pores) was sent into the tiles. 

 Sometimes the drains would keep right on discharging more 

 and more slowly for several days, and sometimes clear on 

 until the next rain, thus emptying the soil of its surplus, and 

 leaving again this 30 inches of porous soil and subsoil like a 

 great sponge all over the tiles, ready to absorb each rain and 

 make its flow into the open streams below far slower, and ex- 

 tended over a much longer time. But the ground adjacent, 

 and not tiled, being soaked full and frozen in December and 

 January, remained frozen full nearly all winter, especially 

 where bare or nearly so. All its depressions were puddles of 

 water frozen into solid ice, and the whole surface was thus 

 without the power of absorbing or filtering scarcely a gallon of 

 each new rain. Thus the untiled clayey land is like a great 



