EFFECT OF MINIMUM DIMENSIONS 



107 



As a substitute for this calculation and to save time, scalers frequently 

 approximate the amount of deduction by guess, based on experience. 



Deducting a Per Cent of Total Scale. The method of deducting a 

 per cent of the total scale, as distinguished from the above methods 

 is chiefly applied to logs containing defects within the log, evidenced 

 by rotten knots, punk, conks, or other indications and whose amount 

 can only be guessed at on the basis of experience obtained by observing 

 such logs as they are sawed in a mill. 



Influence of Log Rule on Deductions for Defects. A log rule based either upon 

 diagrams of 1-inch boards and definite saw kerf, or upon a formula in which the 

 proper deductions are made both for saw kerf and slabbing, permits the scaler 

 to make deductions from the scale of each log separately on the basis of the actual 

 loss in 1-inch boards from that portion of the log included in the scale or log rule. 

 But when a log rule is inaccurate, either because of excessively low valuations, 

 false basis as in converted cubic rules, or erroneous values in formula; as in Doyle 

 or Baxter rules, such deductions when applied to logs already scaled too low would 

 take from the scale more than the proper per cent of defect, as the following com- 

 parison will show. 



A log 10 inches in diameter and 16 feet long, which will saw out but one-half 

 of its scaled contents due to defect (and omitting boards sawed from outside the 

 cyHnder), if scaled by the Scribner and Doyle rules respectively will give: 



If the log is sawed by a mill whose output coincides with the Scribner rule, 

 the over-run on a sound log by the Doyle rule will be 50 per cent. The defective 

 log will give no over-run of sound lumber by Scribner. But if 27 feet, or one-half 

 of the actual sawed contents, is deducted from the scale by Doyle rule the over-run 

 will be 18 feet, which is 200 per cent of the residual scale of 9 feet, on this scale, or 

 four times as great on the defective as on the sound log. By deducting 50 per cent 

 of the Doyle scale for the log, the over-run remains at 50 per cent of the scale as 

 for sound logs. 



Although the method last mentioned gives a consistent basis for making deduc- 

 tions in rules like the Doyle, while the deduction of actual loss in lumber gives 

 far too great an over-run, it is evident that when log rules are used capable of giv- 

 ing a scale equaling but two-thirds of the actual contents, the tendency will be to 

 overlook the defects in scaling unless very serious and numerous. 



90. Efifect of Minimum Dimensions of Merchantable Boards upon 

 these Deductions. Log rules made from diagrams, such as the Scrib- 



