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 + 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 24 16 foot logs; if 56 
feet, 34 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. 
9 a 10” 
Bon 15; 15 squared equals 225. 
4. Subtract 60 from this result and multiply the re- 
mainder by -8, to get the average contents of a 16 foot 
log. 
(225-60) times ,8, equals 132 board feet in average 16 
foot log. 
5. Multiply by number of 16 foot logs in merchant- 
able part of tree, 24 or 34 as the case may be, to get 
contents of the entire tree. This sounds complicated but 
expressed as a formula it reads: 
[(Average diameter?—60)] * .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, 
