114 



THE SCALING OF DEFECTIVE LOGS 



mechanical injuries such as lightning or falling timber. Irregular 

 butt rot, appearing as a small patch on one side, or rot from knots 

 which is local in extent, can sometimes be scaled by the methods used 

 to scale side defects. 



Exterior defects, especially at the butts of logs, may fall entirely 

 outside the inscribed circle representing the top or scaling diameter, in 

 which case they cause no deduction in scale. With defects which 



penetrate deeper a further 

 portion is included in the 

 slab allowed in sawing, 

 within this circle. 



Where the defect ex- 

 tends but a few feet in 

 length, as for instance a 

 fire scar at the butt of a 

 log, the deduction is con- 

 fined to that portion of the 

 length of the small cylinder 

 whose contents is scaled, 

 which is affected by the 

 defect. The amount to 

 subtract may be found in 

 one of two ways; by dia- 

 gram of the slab affected by 

 the defect, or by culling a 

 per cent of the volume of 

 the log. 



Deductions by Slabs. 

 The dimensions of the por- 

 tion to be deducted as a 

 slab are not those of the 

 piece actually slabbed from 

 the butt, but only the depth of the portion lying within the inscribed 

 circle of the small end of log. From this again there is subtracted an 

 additional amount for slabbing, shown in Fig. 20. The remaining 

 depth, multiplied by the average width of the inscribed slab, gives 

 the area of the cross-section whose length will be that of the defect, 



j , a-b-l 



and volume, — — -. 

 15 



In the above figure, the fire scar on the butt log is 8 inches deep, but only 

 5 inches of this is within the inscribed scaling dimensions. Of this lj inches is 

 slab, giving 3f inches for lumber. The widths of the boards lost are 10 inches, 

 14 inches and 18 inches. The average width of the rectangle is 14 inches. A 



Fig. 20.- 



-Effect of fire scar at butt, on deduc- 

 tions from scale. 



