152 FARM DEVELOPMENT 



in each county, and the farmers there have gradually 

 laid tiles on acre after acre until nearly the entire wet 

 area is underdrained, transforming both the agriculture 

 and the sanitation of entire counties. While machinery 

 for laying tiles has been highly developed, for many 

 conditions the spade continues to be the chief imple- 

 ment in opening tile drains. 



Injury of tiles by freezing. In the southern half of the 

 United States there is no danger of frost injuring tile 

 drains. In the extreme northern portions of the country, 

 however, where the earth sometimes freezes to the depth 

 of six or eight feet, the question often arises whether tiles 

 laid two to five feet deep will be ruined by the frost. 

 Where an outlet can be secured so that the water will 

 run freely from the properly laid tiles, there is little 

 danger that sufficient water will remain in them to break 

 the tiles by its expansion under freezing. Where the 

 outlet must be very low, sometimes beneath the water 

 in a pond or stream, the tiles may be full of water when 

 the ground freezes, and in this case its expansion within 

 the tiles may cause them to be split. This may also occur 

 in case the tiles have not been laid on an even down- 

 ward grade, so that the water will not run out of the 

 low sections of the drain. Likewise, where the tiles 

 have been laid in peaty lands which, upon drying out, 

 shrink and settle more in some areas than in others, 

 thus making the line of grade uneven, freezing may work 

 injury. The actual places on record where freezing of 

 water within the tiles has caused them to crumble down 

 and become clogged up and useless, are, indeed, very 

 few, even in states as far north as Minnesota. No doubt, 

 in many cases, where the water upon freezing expands 

 within the tile causing it to break, it simply cracks length- 

 wise, or a number of cracks are produced in such a 

 manner that the pieces all remain in position. The 

 expansion of the ice does not usually cause the pieces to 



