118 



LAND DRAINAGE 



II II 



162. Some convenient aids. 

 To make the succeeding steps 

 more clear, and to illustrate 

 some simple means to assist 

 the operator in establishing 

 grades, and the like, let us 

 take up a piece of actual work, 

 with diagram and the data 

 used in carrying it to comple- 

 tion. 



In Fig. 45, A-B represents 

 the profile of the surface of 

 a portion of a field in which 

 it was necessary to place a 

 tile drain. The distance A to 

 B is 500 feet. In the original 

 drawing, 2 inches horizontally 

 equaled 100 feet, while J inch 

 vertically equaled one foot. 

 Using different scales for the 

 two dimensions destroys the 

 proportions and requires some 

 use of the imagination. A-C 

 represents a fall which provides 

 a good outlet. 



Figure 46 represents the same 

 surface with the grade stakes 

 driven 50 feet apart, accord- 

 ing to directions in paragraph 

 150, and numbered (1-11). 

 Only one finder is shown in 

 place, and that at grade stake 

 7. 



