8 z Infirumental InftruEiions 



To meafnve a lV<3oJ, which, by Reafon of thP" 

 Thkknefs of Trees^ ca?i only be meafurd on 

 the Out' fide. '.. W n ^ 



Fig. 8. ^*T^ H E Truth of this Woil^ 

 X depending wholly on the Ex- 

 aclnefs of Angles, I (hail ufe the Theodolite 

 only. 



, Let the irregular Polygon A B C D E F be . 

 fuch a Wood ^"place the Inttrument at A, and I 

 turn it about, 'til thro^ the fix'd Sights you ' 

 efpy Angle B, and then fcrew it faft. Direft 

 the'index to F, the Index will then cut 104 

 Degrees 5 remove to B, meafuring AB g ch. 

 25 li. At B let the hxd Sights cut Angle Q 

 and the Index Angle A 80 Degrees, fo fliall 

 Angle B be 80 Degrees^ Remove to C, mea- 

 furing B G 2 ch. 5li. 5 at C let the fix'd Sights 

 cut Angle D, and the Index Angle B 2co De^ 

 grees, which exceeding a Semicircle, or 180 

 Degrees, is therefore an outward Angle, and 

 muft be noted thus > . Remove to D, mea- 

 furing C D I ch. 44 li. 3 at D let the fix d 

 Sights cut Angle E, and the Index Angle C, 

 97 Degrees 30 Minutes, fo fliall Angle D be 

 97 Degrees go Minutes. Remove to E, mea- 

 furing DE 2 ch. 65 li.^ at E let the fix d 

 Sights cut Angle F, and the Index Angle D, 

 120 Degrees go Minutes, fo fliall Angle E be 

 1 20 Degrees go Minutes. Remove to F, mea- 

 furing EF ich. 75 li. ^ atF let the fix'd 

 Sights cut Angle A, and the Index Angle E, 



124 



