UNDERDRAINING. 



81 



narrow draining spade (see III. 41) made specially {^Drain " 01 " 



for this purpose. The loose earth is thrown out 



with a "crummer." See III. 42. 



)■■ To secure the proper grade for the bottom of a Grading. 



drain, one method is to use several cross-heads made 



from strips of one-inch boards three or four inches 



43. DRAINING. 



wide. Place the cross-heads so that the cross pieces 

 are in line. The proper grade is ascertained by 

 using an ordinary spirit-level. When ready to lay 

 the drain, set a standard, or the handle of the 

 crummer, on the bottom of the drain, and mark in 

 line with the tops of the cross-heads. This will give 

 a true grade for the tiles. See III. 43. 



