DISCUSSION OF LOG RULES. 51 



SUMMARY. 



No log rule will give an accurate measure of the lumber content of 

 logs of various sizes that fails to properly combine all the factors 

 encountered in converting logs into lumber. These factors are the same 

 for all species under all milling conditions. The value of the factors 

 alone increases or decreases according to the species and method of 

 sawing, but the number of factors remain constant. As a result of 

 failing to recognize the factors that must be combined in devising a 

 properly constructed log rule, by failing to employ all of them, or by 

 combining them improperly, there is no accurate log rule in use appli- 

 cable to variable milling conditions. Any log rule capable of becoming 

 a standard measure and susceptible of correction for certain variable 

 factors must recognize a slab allowance proportional to the barked area 

 of the log, and a sawdust allowance expressed as a definite per cent of 

 the total volume of all logs, not including slabs. The per cent for 

 sawdust is dependent upon the width of the saw-kerf and average 

 dimensions of lumber to be sawed. Other factors to be taken into 

 account are taper, shrinkage, normal crook and excessive taper in small 

 logs, but these are of less importance than the two cited above. 



The following log rules are constructed with a total wastage allowance 

 proportional to the total volume of the log, regardless of size taper not 

 considered : 



Constant] ne, Saco River, Derby, Square of Three-quarters, Partridge, 

 Vermont, Stillwell, Ake, Square of Two-thirds, Orange River, Cumber- 

 land River. These rules are incorrect in principle, therefore no correc- 

 tion is possible. 



Another group of rules is derived by substituting a waste allowance 

 proportional to total volume, plus a constant for logs of different sizes 

 taper not considered. It would seem as though some effort had been 

 made to correct the inaccuracy of the preceding group by adding a 

 constant to compensate for waste occasioned by sawing logs of different 

 sizes. The underlying principles of these rules are incorrect, however, 

 and consequently their values cannot be properly adjusted. Such rules 

 are the following: 



Bangor, Boynton, Parsons, Warner, Spaulding, Hannah, Wilcox, 

 Finch and Apgar, Ropp, Scribner, Favorite, Maine, Herring, Dusenbury. 



Log rules with slab allowance varying directly as the barked area of 

 logs of different sizes and with sawdust allowance directly as the volume 

 after the slab allowance has been made are correct in principle, but are 

 not necessarily correct measures. Rules of this type are as follows : 



Champlain, Boughman's Rotary Saw, Boughman's Band Saw, Wilson, 

 Carey, Baxter, Click, British Columbia, Universal, International, 

 Preston, Doyle, McKenzie. 



Of the preceding rules the Champlain, Universal, International and 

 McKenzie are the only ones that are at all flexible to milling conditions 

 and character of timber to be sawed. The Champlain and the Universal 

 are the same, with the exception of the slab allowance, which in the 

 case of the Universal is twice as great as for the Champlain. The saw- 

 dust allowance for both rules is made by allowing ( 100 ) per 



V 1 + kJ 



cent of the volume of the log (taper not included) for sawdust. This 



