MEASUREMENT OF THE DIAMETER INCREMENT. 



13 



rings ; it is roughly toothed on the other side to assist 

 in extracting the cylinder of wood. 

 (d.) A cradle, D, into which the cylinder of wood is placed, 



after extraction, to prevent its breaking. 



The borer is used in the following way : — 



It is screwed in a radial direction into the tree, at right 



angles to its axis, to the desired depth, whereby a cylindrical 



column of wood enters the hollow borer, and is severed from 



the tree except at its base ; then the wedge is inserted between 



Fiff. 6. — Pressler's Increment Borer, 



the column of wood and the inner wall of the borer, with its 

 toothed side towards the former, and firmly pressed in. This 

 prevents the cylinder from turning round inside the borer 

 during the following operation. The borer is now screwed 

 backward one or two turns, whereby the cylinder of wood 

 is severed at its base from the tree. The borer is now screwed 

 further in, w'hich causes the severed cylinder of wood to be 

 pushed back, until it can easily be withdrawn and placed 

 into the cradle. In this way a column of wood is obtained 

 of about '2 inches diameter and from 2 to 6 inches long 

 according to the length of the borer. The breadth of the 



