DISCUSSION OF LOG RULES. 



15 



for saw-kerf and the balance will be the contents of the log 12' long, 

 from which the others may be obtained by proportion. It would 

 appear from this that a generous allowance for sawdust had been made, 

 but as a matter of fact the apparent sawdust allowance is a part of the 

 allowance already made for slabs. This is clearly illustrated in figures 

 6 and 7, when the above rule is applied. (Deduct 4" from the diameter 

 for slabs and in Figures 6 and 7 we have D 4 = AB. Then, squar- 

 ing the remainder (D 4), we have (D 4) 2 =ABCD. Subtract J 



FIG. 6. The Doyle Log Rule as 

 applied to a 6" log. 



FIG. 7. The Doyle Log Rule as 

 applied to a 30" log. 



for saw-kerf, giving f (D 4) 2 , which is the inside circle. The inscribed 

 circle outside of this is equal to .7854(1) 4) 2 . It is apparent from 

 this that .7854(1) 4) 2 - f (D 4) 2 is the only true portion of the 

 diagram which could represent sawdust.) This rule amounts to the 

 same thing as the Doyle Log Rule, but in statement is misleading and 

 ambiguous. 



The sawdust allowance as shown by Figures 6 and 7 in per cent of 

 total contents after slab allowance has been made is as follows: 



.7854 (D 4) 2 | (D 4) 2 

 .7854 (D 4 ) 2 



100 = 



.0354(7) 4) 2 3.54 



X100= 



.7854 (D -4' 



which is the same as shown by the Doyle Log Rule formula. 



