116 THE BOOK OF FORESTRY 



is in a given log the board foot contents may be ob- 

 tained as follows (the formula for the Doyle log rule) : 



1. Deduct 4 inches from the diameter at the small 

 end (for loss in slabbing the log when sawed). 



2. Square J the remainder. 



3. Multiply by the length of the log in feet. 



A good method for obtaining the contents of a stand- 

 ing tree in board feet is as follows: 



1. Estimate the amount of the tree that will make 

 saw timber in terms of 16 foot logs (if a stick 36 feet 

 long could be cut, it will equal 2J 16 foot logs; if 56 

 feet, 3 logs). 



2. Estimate by eye, deducting for thickness of bark, 

 the diameter at the butt of this log and at the tip, say 

 20 inches inside the bark at the butt, and 10 inches inside 

 the bark at the top. 



3. Square the average of these diameters. 



20" + 10" 

 = 15 ; 15 squared equals 225. 



4. Subtract 60 from this result and multiply the re- 

 mainder by ^ to get the average contents of a 16 foot 

 log. 



(225-60) times ^ equals 132 board feet in average 16 

 foot log. 



5. Multiply by number of 16 foot logs in merchant- 

 able part of tree, 2J or 3 as the case may be, to get 

 contents of the entire tree. This sounds complicated but 

 expressed as a formula it reads: 



[(Average diameter 2 60)] X .8 = contents of aver- 

 age 16 foot log. 



It is a rough and ready rule of thumb that every 

 forester or boy going into the woods should remember. 



The science of forest mensuration is a big subject, 



