92 THE woods^fan's handbook. 



t 

 Table 8 assumes the same rate of growth for the next inch in 

 diameter as the last 2 inches (1 inch on radius). It requires a 

 measurement of the present diameter excluding bark, and a count 

 of rings in the last inch of radius. This is easily done on logged 

 trees, but on standing timber it requires that trees be notched to 

 at least an inch (or the use of the Pressler increment borer «) 

 to get the ring count and bark thickness. When the diameter 

 inside bark is known, and the number of rings in the last radial 

 inch, the volume increment per cent is read from the table. The 

 error for rapid -growing trees is not serious when an approximation 

 only is required. Of course, a number of trees of each diameter 

 should be examined and the average number of rings in the last 

 inch used. 



For a stand of trees the table will apply if the stand is divided 

 into diameter classes and examined in that way. There is more 

 chance for error if an average diameter is taken for the entire 

 stand, unless the variation in diameter is not ver\' great. 



Again, in dense stands some allowance must be made in figur- 

 ing volume growth for the loss through the crowding out of some 

 of the trees. 



a See page 110 for description of this instrument. 



