GRADING THE DITCHES FOR TILE. 



105 



ing all kinds of drains. It depends upon the same 

 principle as that described for setting the line, and con- 

 sists of setting crossbars at the stakes instead of a line 

 and then testing the bottom by a line of sight over a 

 rod of the same length as that at which the bars are 

 set above the grade line. Figure 25 will make the 



Fig. 25.— Grading by Sight Line and Target 



manner of using them plain. The targets, as they are 

 called, are bars of wood about 3 feet long, and are 

 attached to an iron rod by means of adjustable clamps, 

 each of which is made tight by a thumb-nut. The 

 target can be moved up or down upon the rod or set 

 at any angle desired. The iron standard can be thrust 

 into the ground where it will remain firm, and the head 

 levelled and brought to the required height, at which 

 point it can be made fast by the thumb-nut. When 

 two of these are set, the grade line can be worked to 

 in the manner shown in the cut. One target should 

 be painted red, the other white, to aid in drawing a line 

 of sight over them. Whenever there is a change of 

 grade the target should be reset, and at such times ^ 

 third target is necessary. 



The only objection to this method is that some work- 



