CHAP, v.] EXAMPLES OF IRREGULAR PLOTTING 131 



(in this case considered as fixed) from which to measure the 

 bearing, must be, in transferring it from A B, corrected for 

 the convergency due to the distance A X, by, after ruling a 

 line through X parallel to A B, laying off at X, from the parallel 

 just ruled, towards the pole, and on the side of A, an angle 

 equal to the convergency required, which will give the direction 

 of the true meridian. 



The system of true bearings may be used in many ways Further 

 whilst carrying on an irregular triangulation. It is impossible TrueBear. 

 to give instances of all the difficulties which may be sur- ings. 

 mounted by this means, but examples taken from actual prac- 

 tice will show the style of use to which true bearings may 

 be put. 



EXAMPLES OF IRREGULAR PLOTTING. 



Example I. — One inaccessible object visible from both terminal 

 astronomical positions and from two or more intermediate 

 stations. 



Fig. 24 is an illustration of irregular plotting. A and B 

 are astronomical observation spots at the extremes of a 



Fig. 24, 



survey, from both of which the high, inaccessible peak C is 

 visible. D, E, F constitute a chain of intermediate stations ; 

 A and D, D and E, E and F, F and B being respectively 



9—2 



