MEASUREMENT OF LOGS AND OTHER FOREST PRODUCTS 121 



and to credit only the amount which the log will actually saw out 

 in merchantable lumber, according to the standard agreed upon 

 between buyer and seller. 



The "merchantable timber" may be the basis on which the 

 scaling is done, in which case there is always a chance for argu- 

 ment between buyer and seller. It is better policy to specify 

 that the buyer must take all timber that will produce at least a 

 specified grade of lumber. 



Scahng defective logs requires expert judgment and long ex- 

 perience as there are a great variety of defects possible and the 

 determination of the extent to which they influence the sawing 

 contents of the log must be left entirely to the scaler. Rules for 

 discounting unsound logs are of value chiefly as a check on the 

 scaler's judgment. The latter becomes expert through study- 

 ing defective logs as they are sawed in a mill and actually 

 determining the amount of sawed material that logs with given 

 defects will yield. This varies with the species, character of 

 lumber manufactured, type of saw used, efficiency of the 

 sawyer and the degree of utilization in the manufacturing 

 plant. 



Among the defects common to timber are center or heart rot, 

 shake, pin-dote, cat-face, rotten sap, deep checks and seams, 

 crook, crotches, stained sap and rafting pinholes. 



Uniform Center or Circular Rot. — There are a number of 

 methods in use for discounting this form of defect. 



(i) Assume the scahng diameter of the log to be the diameter 

 minus the diameter of the rotten core. Thus, if a 12-foot log 

 were 20 inches in diameter and the rotten core had a diameter 

 of 6 inches, the scaling diameter would be 14 inches. The loss, 

 using the International rule, would be 125 board feet, or 53 per 

 cent of the total. 



(2) Scale the log as sound, compute the contents of the rotten 

 core and subtract this from the gross scale. The loss in the log 

 above cited would be 15 feet, or 7.3 per cent. 



(3) Add 3 inches to the diameter of the defect, square the sum 

 and deduct this from the full scale of the log. This method 

 shows a loss of 81 feet, or 34 per cent. 



