This section is from the book "Scientific American Reference Book. A Manual for the Office, Household and Shop", by Albert A. Hopkins, A. Russell Bond. Also available from Amazon: Scientific American Reference Book.
The ratio between the number of board feet and cubic feet in logs depends on the species of tree, on the size of the logs, and on the method of scaling. The ratio for standing trees depends, further, on the minimum size of the merchantable log. For example, the ratio would be different, if 4 logs were cut from a tree, from the result if only 3 logs were taken. Satisfactory figures can, therefore, be obtained only by comparing the scales of logs and trees actually measured in the woods. Such tables are now being prepared by the Bureau of Forestry for different species in different regions.
 
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