98 ENGINEERING FOR LAND DRAINAGE 



in platting is shown in Fig. 2 1 . The semicircle part 

 of the protractor should be placed in the direction of 

 the course to be marked and the angle read from the 

 north end of the protractor for all bearings beginning 

 with N and from the south end for bearings beginning 

 with S. 



Making the Map, 



Determine first how large it is desired to have the 

 map and the scale that can be used. The measure- 

 ments in the field have been taken and recorded in 

 stations of lOO feet, so a convenient scale for represent- 

 ing the lines will be a certain number of hundred feet 

 to one inch. The more detail work it is desired to 

 represent on the map the larger should be the scale 

 200 to 300 feet to i inch are good scales for farms 

 of moderate size, while for large tracts 500 to 1000 

 feet must be used in order to keep the size of the 

 map within convenient limits. Lay off the boundary 

 of the farm or tract according to the proposed scale. 

 Locate the position of the outlets of the drains and 

 work upward in laying off the lines in the same man- 

 ner and order as the survey was made. Number the sta- 

 tions where angles occur, where branch drains enter, 

 and also the number of the station at the upper end of 

 each drain line. All angles should be laid off with the 

 protractor, and the intersection of the drain lines with 

 field or fence lines, and in large tracts with land lines, 

 should be shown. All of this outline work should be 

 done in light pencil lines, and when completed re- 

 drawn in ink* In working maps the drain lines are 

 usually drawn in red^ all others in black. For a finely 



