No. 4.] HINTS ON LAND DRAINAGE. 383 



are certain to gape open upon one side or another, and thus 

 admit silt more readily. A tile, however, which can be laid 

 upon any one of six or eight different sides can be turned 

 and tried upon all of them until a close joint is secured. 



"Sole" tile of the same nominal size has less capacity, 

 because the bore is elliptical, and its size is designated by 

 its longer diameter. It has, moreover, only one bed, and 

 hence it is impossible to make so good joints in laying it. 

 "Round" tile have the same capacity as " Ohio," but, hav- 

 ing no flat surface upon which to lie, they are less stable in 

 the trench before covering, and therefore more liable to be 

 thrown out of line in backfilling. In the Boston market 

 both round and sole tile are somewhat higher in price than 

 the Ohio tile. 



Silt basins should be placed at the intersection of laterals 

 with main drains and at all points where there is a change 

 in direction, also where there is a change from a steeper to 

 a flatter grade. A simple method of making a silt basin is 

 by placing a vitrified sewer pipe of ten inches or greater 

 diameter vertically, or upon end, in the line of the drain or 

 drains leading into and from it. The bottom of the pipe 

 should rest upon a plank or flat stone about a foot below 

 the drain, and with the bell end upward. Lead the drains 

 into and out of it through holes of proper size cut in the 

 sides of the pipe at their proper level. In the bell at the 

 top of this pipe set another of the same size, and so extend 

 the silt basin either up to the surface of the ground or to 

 within about a foot of it, according as it may be more de- 

 sirable to cultivate over it without obstruction, or to have it 

 always accessible for inspection and cleaning out without 

 digging. Where it is to be covered, the top should be 

 closed by a circular cover of plank or stone set in the upper 

 bell end, and its location marked by a stake driven beside 

 it, so that it may be occasionally uncovered and cleaned out 

 so long as there shall continue to be any accumulation of silt 

 in it. Where the silt basin extends to the surface of the 

 ground, small animals and foreign matter should he excluded 

 in a similar manner by a cover of wood, stone or iron, fitted 

 and set into the bell of the pipe. 



