122 ENGINEERING TOR LAND DRAINAGE. 



the proposed grade line or bed upon which the tiles are 

 to rest. 



Grading the Bottom. — The ditch must be dug to the 

 depth indicated by the figures given with the survey, 

 which depth is to be measured from the grade stakes 

 which are set for that purpose, and graded evenly on 

 the bottom by means of the '' line and gauge ' ' method, 

 or *< target, '* or any other equally accurate device for 

 obtaining an even and true bottom upon which to lay 

 the tile. The bottom must be dressed with the tile 

 hoe, or in case of large tiles, with the shovel, so that 

 a groove will be made to receive the tile, and when 

 laid in it they will remain securely in place. 



Laying the Tile. — The laying of the tile must begin 

 at the lower end and proceed up-stream. The tile 

 must be laid as closely as practicable, and in lines free 

 from irregular crooks, the pieces being turned about 

 until the upper edge closes, unless there is sand or fine 

 silt which is likely to run into the tile, in which case 

 the lower edge must be laid close, and the upper side 

 covered with clay or other suitable material. When, 

 in making turns, or by reason of irregular-shaped tile, 

 a crack of one fourth inch or more is necessarily left, 

 it must be securely covered with broken pieces of tile. 

 Junctions with branch lines must be carefully and 

 securely made. 



Blinding the Tile. — After the tile have been laid and 

 inspected by the person in charge of the work, they 

 must be covered with clay to a depth of six inches, 

 unless, in the judgment of the superintendent, the tile 

 are sufficiently firm, so that complete filling of the ditch 

 may be made directly upon the tile. In no case must 



