CHAPTER VIIL 

 GRADING THE DITCHES FOR TILE. 



The engineer should be thoroughly conversant with 

 practical tile-laying and with the best plans for secur- 

 ing the most accurate work. Workmen can frequently 

 dig the ditch, but do not understand the principles of 

 grading it accurately according to survey. Many work- 

 men think that it is more difficult to do than it is, 

 hence the engineer should seek to make the whole 

 matter plain. A survey should be carefully worked to 

 or its full value cannot be realized. There are two 

 good plans for grading a tile ditch, both of which de- 

 pend upon the same principle and both simple and 

 practical. 



The Line Method. — This consists of setting a line or 

 wire directly over the grade stakes at a given distance 

 above and parallel to the bottom of the proposed ditch. 

 As the bottom is finished for the tile it is tested by 

 means of a gauge which carries a light crossbar set at a 

 right angle to it. The line is stretched parallel to the 

 grade line of the ditch and $ feet above it, which is 

 a convenient height, and tested by the gauge which is 

 5 feet long from the bottom to crossbar. The line 

 should be supported at two or three points between 

 stations to prevent sagging. 



