BOARD MEASURE 145 



log contains 2 ft. B. M. per foot of length, an 8-inch log 

 2j ft., a 9-inch log 3 ft., a 10-inch log 4 ft. 



One notable thing about the New Brunswick rule is that 

 taper is allowed for in lengths over 24 feet. 



7. Quebec Rule. This is the legal rule for measuring 

 logs in the province of Quebec. Values are close to the 

 Scribner Rule; in many cases they are identical. The 

 figures were derived by plotting. 



8. Theory of Scale Rules and Clark's International 

 Log Rule. The theory of the measurement of saw logs 

 in board measure has been more carefully studied by 

 Dr. Judson F. Clark 1 than by anyone else, and a rule 

 called the International Log Rule was devised by him, 

 on the basis of this reasoning, which he also tested at 

 the saw. The main points in this study are as follows : 



Taper of Logs. While logs exhibit a great variety of 

 taper, it has been found (1) that rough logs taper more 

 than clear, smooth logs, so that quality tends to neutralize 

 taper ; (2) that average taper does not differ greatly in dif- 

 ferent localities or with different species. This average 

 taper as a result of much measurement is found to be 

 safely 1 inch in 8 feet. This in modern economical mill 

 practice increases the yield of lumber in the form of side 

 boards, and the above stated allowance for taper is there- 

 fore introduced into the rule for all lengths over 8 feet. 



Crook and Sweep. In this study due allowance was 

 made for irregularity of surface, and crook averaging 1^ 

 inches in 12 feet of length, found to be characteristic of 

 white pine logs on the Ottawa River, was counted normal. 

 Above the limit of ij inches in 12 feet, any given degree 

 of crook was found to affect the product of small logs more 

 than of large logs, and that in proportion to their diameters. 

 That is to say, a crook of 3 inches in 12 feet throws out 

 twice as great a percentage from a 10-inch log as from one 

 20 inches in diameter. 



Shrinkage and Seasoning. Logs are commonly scaled 

 green, while sawed lumber must hold out on a survey made 

 when it is dry. In computing his rule Dr. Clark figured 

 that boards would be cut 1^ inch thick to allow for this. 



1 See Forestry Quarterly, Vol. IV, No. 2. 



