THE TRANSIT 83 



they may be more than 180. The magnetic bearings 

 may be used to figure out the angles as a check on 

 measurement; they also help to locate an error if one 

 exists, but a more accurate check is the sum of all the 

 angles which should equal twice as many right angles 

 less four as the figure has sides. 



Computed bearings are worked out by applying the 

 angle measurements to the bearing of the first line. Com- 

 puted, not observed, bearings should be used for plotting 

 or for computing traverse. Notes may be kept as follows: 



48.19' 



819.96' 



SKETCH OP SURVEY 



Instead of interior angles, deflection angles may be 

 read, a deflection angle being the angle which any course 

 makes with the prolongation of the one preceding. To 

 get this, after the instrument has been turned on the rear 

 point, revolve the telescope on its axis and turn to the point 

 ahead. The deflection must be recorded as right or left, 



