THE BILTMORE STICK 231 



„ , aD 



^a{a+D) 



Since BC is the scale for \ of the diameter of the circle, the formula for the scale 



for the whole circle is ' 



aD laD^ 



Scale =^=^^ =\—-f:- 

 Vaia+D) \a+D 



The Biltmore stick is less accurate than the cahpers or diameter 

 tape and should therefore never be used for scientific measurements or 

 permanent records. To insure complete accuracy in the use of a prop- 

 erly graduated stick, the following conditions are necessary : 

 The tree must be circular in cross-section. 



The stick must be held against the tree at a point 4^ feet from the 

 ground. 



aD VaVaD VaD j aD'- 



Va{a+D) VaVa+D V^+D \a+D' 



