SCALING PRACTICE 91 



the scale for all visible defects which he within the cylinder in each 

 log separately, of the amount of lumber which would be lost because of 

 the defect. 



This rule is not always observed. In many species, certain defects may exist 

 without visible external indications either on the surface or at the exposed ends. 

 When the logs are in water it is difficult to detect defects. There has been a 

 tendency on the part of makers of log rules to reduce the standard volumes of the 

 log rule in order to offset these invisible defects (Scribner rule, § 68). Log rules, 

 like the Cumberland River rule which gives but 45 per cent of the cubic contents, 

 permit the buyer to ignore most defects with perfect safety. 



The use of a log rule which is known to give a large over-run (§ 47) usually 

 gives rise to the practice of scaling "sound" and ignoring defects. The buyer 

 can afford to be lenient, and the seller objects to any further discounts than those 

 inherent in the rule itself. 



Except for a few species and regions, defects may usually be seen and 

 deducted. Where the opposite is true, custom sometimes permits a 

 reduction of the final scale by a straight per cent to allow for such 

 invisible defects. 



Over-run (§ 46) is therefore an element which should not influence 

 in any way the practice of log scaling. Where an admittedly defective 

 rule is offset by lenient but inaccurate scaling practice, the entire 

 technique and standard of scaling suffers, and such conditions should 

 sooner or later yield to accurate standards, both in the rule used and 

 in its application. 



83. Scaling Practice, Based on Measurement of Diameter at Small 

 End of Log. The advantages of measurement of the log at the small 

 end, which have made this custom practically universal in scaling, are 

 that the scaling diameter inside the bark can be directly measured 

 without guessing at bark thickness, and no matter how high a skidway 

 or railway is piled, the ends of the logs are usually visible for scaling. 

 By contrast, logs to be calipered at the middle point can be measured 

 only when lying separately or before being placed on railways, and the 

 bark thickness is usually guessed at. 



The per cent of over-run on the log scale is affected by three main 

 factors. Two of these, namely, the elements affecting manufacture of 

 lumber and the character of the log rule itself, have been discussed in 

 Chapter V. The third is the practice of scaling, and the customs which 

 govern it, collectively termed the " scale." This practice affects, first, 

 the method of determining scaling diameters and lengths, for when 

 these are once ascertained the rule permits no variation in contents for 

 sound logs; and second, the deductions from this scale for defects, as 

 interpreted by the scaler. 



Scaling Lengths. The total length of a log must be accurately deter- 

 mined. For log rules which are based on diameter at the small end, 



