Volume Determination 337 



A simpler application is to list the average log for each size 

 of D. I. B. and multiply this result by the total number of logs 

 tallied in trees of each D. I. B. 



The simplest application of the rule to individual trees is to 

 memorize this figure for each D.I.B. or to memorize the scale 

 rule and compute the scale of a tree whose volume is desired. 

 In this connection, it will be found that three times the radius 

 squared will give approximate results for IG' logs over 24" in 

 diameter. 



Another rule of thumb has been devised by Lumberman Girard 

 which is also dependent on the scale. It has the advantage of 

 being obtained from the breast height measurement of trees out- 

 side the bark rather than an estimated diameter inside the bark at 

 a point which can not be reached from the ground. It has been 

 carefully checked over and seldom varies over 4 or 5 per cent 

 from actual measurements of groups of trees, usually less than 

 2 or 3 per cent. It is subject, however, to variations in individual 

 trees above or below the average. 



This rule is to add 6 inches to the D.B.H., divide by 2 and 

 use this result for the diameter of the average log. The scale 

 corresponding to this diameter multiplied by the number of logs 

 gives the volume of the tree. Thus a tree 24" D.B.H. with 5 logs 

 will be computed as follows : 



24+6 



= 15", scaling 140 ; 



2 

 5X140=700 feet B.M. 



This rule will hold for White pine and spruce cutting to a 

 6" top and for larch cutting to an 8" top. For Douglas fir cutting 

 to an 8" top add 4" instead of 6"; for Lodgepole pine cutting 

 to a 6" top add 5"; for Yellow pine under 20" add 6"; 20 to 

 25" add 8"; 26" and over add 10", or for all sized Yellow pine 

 add 8" straight. 



A volume table or table of average logs may be made up from 

 this rule similarly to that described above. Neither of these rules 

 makes any allowance for breakage or defects. 



