LAYING OUT DRAINS IN THE FIELD. 83 



correcting the azimuth, make corrections on the notes 

 according" to the following rule. 



To Reduce Magnetic Bearings to Trtce Bearings. 



When the variation is east, as in Western and South- 

 ern States, for bearings N. and W. or S. and E. sub- 

 tract declination from magnetic bearing. For bearings 

 N- and E. or S. and W. add declination to magnetic 

 bearing. 



When the variation is west, as in the Northeastern 

 States, for bearings N. and W. or S. and E. add dec- 

 lination. 



For bearings N. and E. and S. and W. subtract dec- 

 lination. 



Now that wire fences and other improvements made 

 of iron and steel are in such common use, care must be 

 taken to keep the compass distant from all iron and 

 steel, which of course will deflect the needle and destroy 

 the reliability of its readings. Should it be necessary 

 to obtain the bearing of wire fence line, an ojfifset of 

 30 feet may be made and the bearing of the parallel 

 line be read. 



Keeping Compass Notes. 



The running form of keeping notes is simple and in 

 common use. For example, in recording the notes of 

 drains, the following running notes may be written on 

 the right-hand page of the level-book. 



DRAIN NO 2. 



Sta. o to 6 N. 10° 30' E. 



6 to 8 N, 4°oo'E. 



8 to 15 N, 32"* 00' W. 



15 to 22 (end).. N. 15° 20' W. 



it 



