MEASUREMENT OF THE DIAMETER. 



11 



(3) In the case of excentric or elliptic trees, two diameters 



at right angles to each other must be measured and the 

 mean taken. 



(4) The height fixed for the measurement must be strictly 



adhered to. 



(5) In the case of trees which 



are divided into two or 

 more limbs below the 

 fixed height of measure- 

 ment, each limb must be 

 measured and recorded 

 as a separate tree. 



(6) The calliper must be placed 



at right angles to the axis 

 of the tree, and the rule 

 must touch the tree. 



(7) The reading must be 



taken while the calliper 

 rests on the tree, and not 

 after it has been with- 

 drawn. Fig. 4. The Tree Compass. 



c. The Tree Compass. 



The shape of this instrument will be understood on reference 

 to Fig. 4. The diameter of the tree or log is taken by the 

 two points c and d, while it can be read off at li on the arc/, g. 



In order to produce sufficient stiffness in the arms of the 

 compass, they have to be made of metal, which makes the 

 instrument very heavy and unsuited for continued use. 



d. Dendrometers. 



In some cases certain dendrometers are used to measure the 

 diameter of trees at some height from the ground. The theory 

 is this : 



The angle which is formed by two rays running to the two 

 sides of the tree is measured, as well as the distance of the eye 



