122 LOGGING 



(4)^ " For uniform defect of 3 inches or less in diameter, deduct 

 10 feet b.m. in logs up to 16 feet in length. 



"For defect 4 to 6 inches in diameter add 3 inches to actual 

 diameter of rot, and deduct from the full scale of the log an 

 amount equal to the contents of a log of the resultant diameter. 



"For defect 7 to 12 inches in diameter add 4 inches to diam- 

 eter of rot and deduct an amount equal to the contents of a log 

 of the resultant diameter from full scale of log. 



"In short logs showing defect less than 4 inches in diameter 

 at only one end and not in the knots deduct one-half the amount 

 called for by the rule for the full length of the log. 



"In measuring the diameter of this t^-pe of rot the scaler 

 should measure it at the end of the log showing the greatest area 

 of defect, since the saw cuts in straight parallel lines." 



Using the International scale the above method gives a loss on 

 a 12-foot log, 20 inches in diameter and with a 6-inch rotten core, 

 of 40 feet, or 17 per cent. 



The wide variation in the results secured by these different 

 methods shows the weakness of the average systems employed. 



In "Forest Mensuration,"- certain defects are classified, and 

 tables showing the discounts are given. A cull table for center 

 rot taken from this volume follows. It is based on a study made 

 by Tiemann which established the fact, theoretically, that "in 

 logs of the same length, the loss due to holes of any specified size 

 is practically uniform regardless of the size of the log." 



Although the table is designed to be "appHcable to all center 

 defects, such as holes, cup shake, rot, etc., which are 4 inches 

 or more from the bark," it is less accurate for holes than for 

 rot. 



In actual sawing practice there is a difference in the loss of 

 timber in two logs of a given size, one of which has a rotten core 

 of a certain diameter and the other a hole of the same diameter. 

 When sawing a hollow log enough timber must be left around all 

 sides to hold against the carriage dogs and prevent the saw from 



* Method used by the U. S. Forest Service. 



2 Forest Mensuration, by Henry Solon Graves. John Wiley and Sons, New 

 York, 1906, p. 71. 



