DISCUSSION OF LOG RULES. 7 



sions. The Spaulding, Scribner and all other log rules with a waste 

 allowance for slabs varying directly as the volume of the log are math- 

 ematically incorrect, since there is no reason for cutting any thicker 

 slabs from large logs than from small ones. 



Another principle underlying the measurement of lumber contained 

 in logs of different diameters and lengths is the relation of the allowance 

 for sawdust to the size of the log. Since the waste allowance which 

 should be allotted to slabs should be proportional to the barked area, 

 it can be met by reducing the diameter of all sized logs a constant 

 amount, and the remaining volume can then be considered as lumber 

 plus sawdust. It is very evident that the sawdust allowance depends 

 upon the dimensions of the lumber to be sawed and upon the width of 

 the saw used. It is also evident that, for any specific width of saw-kerf 

 and dimensions of lumber to be sawed, the allowance for sawdust should 

 be a definite per cent of the total volume of all logs, not including slabs. 

 A sawdust factor which fulfills these conditions is as follows : 



Where k = width of saw, in inches. 



w = average width of lumber to be manufactured, in inches. 

 t= average thickness, in inches. 



This factor shows what fractional part of the log minus allowance 

 for slabs should be allowed for sawdust. 



represents the fractional part of the log after slab allowance is made, 

 which becomes lumber. 



Log rules which ignore these principles can not be any more than 

 local rules, applying to conditions existing at very few mills. 



There are several other considerations to be taken into account in 

 constructing a log rule, which are not of such vital importance as the 

 two principles cited above. They are allowances for taper, shrinkage, 

 normal crook and excessive taper in small logs. All of these factors 

 depend largely upon the character of the timber, and should be adjusted 

 accordingly for the different species, and for the same species growing 

 under different conditions. 



THE THREE RULES MOST COMMONLY USED. 



The Spaulding Log Rule. 



The Spaulding Log Rule is the statute rule of California, having been 

 adopted by an act of the legislature in 1878. It is constructed from 

 diagrams, and the following comments upon it were published by its 

 author : 



"Each sized log has been scaled so as to make all that can be 

 practically sawed out of it, if economically sawed. Each log to be 

 measured at the top of small end, inside of the bark, and if not 

 round, to be measured two ways at right angles and the average 



