22 A MANUAL FOR NORTHERN WOODSMEN 



country where local attraction is infrequent it is sufficient 

 precaution to watch the blazes and bushing back along the 

 line. In any case, time is saved by setting up the com- 

 pass approximately by the backsight before letting the 

 needle go free. 



2. TRY-LINES 



When two unconnected points are to be joined, it is usual 

 first to run a line without spotting, a try-line so called, and 

 if the desired point is not hit, to measure at right angles the 

 distance between the line run and the point aimed at, fig- 

 ure the angle of error, and rerun the line. The angle re- 

 quired is obtained from a table of tangents. 



Thus suppose a try-line to have been run N 4 E 120 

 rods or 30 chains and to have hit 32 links east of the mark 

 aimed at. Dividing 32 by 3000 (the distance run in links) 

 gives .0107, and the angle of which this is tangent is 

 found in the table of natural tangents to be 37'. The com- 

 pass may therefore be set N 3 23' E, and the line rerun. 



Results near enough for most purposes may be had by 

 remembering that the tangent of 1 is .0175 (i. e., if feet in 

 100, or if links per chain) and that the tangents of small 

 angles are in proportion to the size of the angles. Thus 

 with the case above, the tangent of 1 being .0175 and 

 that of the angle required .0107, .0107 divided by .0175 

 equals .61 of 1, or 37'. 



a c i . ; L__i___|Trial Line 



Sch. 10 ch. 15 ch. 20 ch. 25 ch. 30 ch. 



DIAGRAM SHOWING THE METHOD BY OFFSET 



Or instead of using the compass to rerun the line, its 

 position may be fixed by offset, that is, by measuring at 

 right angles to the try-line, at different points along it, the 

 distance required to place points in the desired range. For 

 this purpose stakes should be left in the try-line at equal 

 distances apart, say every 5 chains, and the length of each 

 offset may be figured by tangents or as a simple problem 

 in proportion. 



