LAYING OUT DRAINS IN THE FIELD. 79 



profile represents the approximate relation of surface to 

 grade line, but does not indicate the cuts at each sta- 

 tion sufficiently close for use in detail construction. 

 Every profile should have a name or heading by means 

 of which it can be connected with the notes from which 

 it has been made, or with the surveyed line on the 

 ground which it represents in section. Profile paper 

 used for this work is sold by houses dealing in engineers* 

 supplies. 



Compass Surveying for Drainage Work. 



The data for platting farm and field lines, locating 

 preliminary level points for topographical work, drain 

 lines, etc., can be most rapidly obtained by use of the 

 compass. A level equipped with a small compass suit- 

 able for field work is convenient and very serviceable. 

 The needle indicates the magnetic meridian, an ap- 

 proximately north and south line. The true meridian 

 is a true north and south line, which if produced would 

 pass through the poles of the earth. 



The compass circle (Fig. 16) is divided into degrees 

 and fractions of a degree. The letter E. , denoting east, 

 is at the left hand, and W., denoting west, at the right 

 hand of the box, which is contrary to the position of 

 these letters in the small pocket compasses. This 

 arrangement is necessary because in using the field com- 

 pass the box is turned so that the sights point in the 

 direction of the line whose azimuth is to be obtained. 

 The north end of the needle is read, which gives direct 

 the azimuth of the line or the angle which it makes 

 with the magnetic meridian. 



