32 



" 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 impos- 

 sible to make so good joints in laying it. " Round " tile have the 

 same capacity as " Ohio," but, having no flat surface upon which 

 to lie, they are less stable in the trench before covering, and there- 

 fore 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 sam.e 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 desirable to cultivate over it with- 

 out 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 be excluded in a similar manner 

 by a cover of wood, stone or iron, fitted and set into the bell of 

 the pipe. 



It goes without saying that the best time in which to construct a 

 system of land drainage, other conditions being equal, is during 

 seasons of long-continued drought, such as have occurred during 

 the open season of 1894 and up to the present time this year. 

 Then the level of the ground water, or the water table, is reduced 

 to its lowest natural limits, and the work can be carried on at less 

 cost and done in a more thorough manner by reason of the absence 

 of water. Moreover, as a rule, the drains may be laid at a greater 

 depth at such times than when the ground is full of water. 



WILLIAM WHEELER, 



Engineer, 



