150 ENGLISH WOODLANDS 



felled and barked, it will frequently be found 

 that this allowance is somewhat in excess of an 

 accurate measurement. 



The height of a tree which it is desired to 

 know with greater accuracy than is possible 

 by estimation can be measured, if the tree is 

 in such a position that an observer can stand 

 level with it and measure the ground between 

 himself and the foot of the tree. (1) With a 

 pocket clinometer an observer can find the place 

 where the top of the tree makes an angle of 

 45 degrees with his eye, then the distance from 

 himself to the foot of the tree, plus the distance of 

 his eye from the ground, equals the height of the 

 tree 1 ; or (2) by the relation of similar triangles. 



Take two poles of different lengths, push the 

 smaller one into the ground until the top is 

 at a convenient height for the eye, say 5 feet, 



B 



1 In the triangle A 



C A 



If the angle at C = 26 34 then A B = $ C A nearly 

 = 35 A B = A- C A 

 = 38 40 A B = $ C A 

 =45 A B = C A exactly. 



and put the longer pole 3 feet in front of it 

 and between it and the tree. Take two imagin- 

 ary lines from the top of the smaller pole, one 

 to the top of the tree and one to the point on 



