6S ENGINEERING FOR LAND DRAINAGE. 



The work should be done at a time when growing 

 crops will not interfere with running the lines. 



It would appear upon first considering work like this, 

 especially to one who has not tried it, that obtaining 

 the data before described would involve considerable 

 time and labor. It may be said, however, that i6o 

 acres of ordinary prairie farming land may be surveyed 

 as above described — two chainmen with stakes, fol- 

 lowed by levelman and rodman — in two days. 



The Map. — All necessary information is now in tab- 

 ular form on the field-book. Make a map of the farm 

 by first adopting a scale and platting the boundary 

 lines according to notes and measurements taken in the 

 field and recorded in the book. One half inch to lOO 

 feet is a good scale to use for a farm of i6o acres. 

 Reproduce the lines laid off in the field so that the 

 plat will correctly represent the field on the scale 

 adopted and used. (Fig. 13.) 



Now write the elevations as found in the field-book 

 at the intersections of the lines on the plat, which in- 

 tersections represent the position of the stakes which 

 were set in the field. 



The plat now shows the comparative elevations of 

 these points over the entire farm, and also such other 

 features as may have been noted in making the survey. 

 The contour lines may now be drawn from the eleva- 

 tions which are shown. The vertical distance between 

 them may be any unit it may be convenient to adopt. 

 In the example here given, the distance is one tenth of 

 a foot. They are numbered in order of elevation. 

 The plat now shows at a glance the degree and direc- 

 tion of slope of any part of the tract. The elevation 



