No. 7. DEPARTMENT OF AGRICULTURE. 511 



face of the soil. Rains come and the soil is thoroughly saturated 

 with water. If the soil is coarse or fine, the water table gradually 

 lowers accordingly if an outlet is provided. Here is one tile drain 

 and here is another over there. As the soil is saturated with water, 

 it commences to pass off through the drains. The water table in the 

 soil gradually lowers slower and slower until it gets near the grade 

 line. The water directly over and around each drain is the first to 

 flow away to the depth of the drainage system. If drains are placed 

 three feet deep, they would not drain to that depth over here, mid- 

 way, probably only two and a half feet deep. If we place the drain- 

 age system three feet deep we do not drain all the land to that depth 

 but perhaps around two and a half feet. Something must be allowed 

 for the flow of the water through the soil. Now as the water goes 

 down and out we can see how effectually the drains work. It will 

 dry up wet stagnant soil so that it will grow any ordinary crop. I 

 want to clear up one point. As the water goes down — just remember 

 it is only the surplus and free water that the tile drainage system 

 removes from the soil. As the water goes to the drains, each small 

 soil particle retains a little bit as film moisture. This amount of 

 film water ranges from fifteen to twenty per cent, of all the water 

 a soil will hold. This soil above the water table — the drain level, has 

 retained by surface tension all the moisture it needs. As the water 

 lowers down to this drain level the excess water flows away by 

 gravity off through the drains and capillary attraction being re 

 established brings the water from below this level up towards the 

 surface. Drainage does not interfere with the sub-soil water below 

 the drains. We have just as much water below the drains as we ever 

 had whether soil is drained or undrained. Capillary attraction 

 brings up the sub-soil water from unbelieveable depths. The finer 

 the soil particles, the smaller the spaces which form tiny like hair 

 tubes throughout the soil. They form channels, vertically, horizon- 

 tally and diagonally in every direction. Now capillary attraction is 

 the force which brings the water from lower to higher levels just as 

 soil rises in and by the lamp wick to the flame. The water passes 

 out of the soil by and through these same channels according to 

 gravitation along the lines of least resistance. Water leaves the soil 

 in obedience to the laws of gravitation. Drains have no magical 

 power to draw or extract water from the soil. A cubic foot of water 

 weighs 62^ lbs., and it is easy to see how water is compelled drain- 

 ward. Here is a cubic foot of water weighing 62^ lbs., and another 

 right here on top of same. It is easy to figure out the pressure on 

 each 144 square inches of area. But the soil sort of dams up, stops, 

 holds back the flow of water through the soil, so we do not get the 

 full pressure. Here is a side view of the tile drain. The soil spaces 

 nearest the tile joints are the first ones to flow into the tile. Next, 

 the excess water from the soil flows into the empty spaces, then into 

 the tile drain at the joints and not through the walls. The bulk of 

 the water goes in a drain that way at the tile joints. It is too slow 

 a process for it to ooze through the walls of the tile. Then the soil 

 spaces nearest those emptied are the next to flow drainward. This 

 flow of excess water drainward continues upward and laterally until 

 an equilibrium is established throughout the soil. That is the way 

 a tile drain relieves the soil of excess water. 



Tile drainage is a permanent paying investment. I will now try 

 to show you how we applied it. We had to do a good deal of drain- 



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