150 A MANUAL FOR NORTHERN WOODSMEN 
foot log takes but a small percentage out of its total yield 
at the saw, while a 6-inch log with the same sweep is 
practically useless for full length, edged lumber. Again, 
strong taper may largely neutralize the effect of consider¬ 
able irregularity in outside form. Lastly, in practical 
scaling, a certain amount of irregularity in outside form 
must be considered normal and be taken care of by the 
conservatism of the log rule. 
Shakiness in logs is far more frequent in some species 
than in others. Thus hemlock is largely affected by it, 
while there is very little of it in spruce. In large measure, 
it should be considered as an element of quality, affecting 
the grade of the product, not a defect affecting the scale of 
the logs. When, however, a considerable section of a log 
is rendered worthless, it should be thrown off in the scale. 
How much to throw off is a matter of judgment and of mill 
experience. 
Decay may be complete, utterly destroying the value of 
a whole log or a section, or it may be partial, allowing the 
production of a low grade of lumber. Decay varies much 
according to species and locality, and it occurs in various 
forms. Of the northern soft-wood trees, fir is most liable 
to unseen defects, — a log perfectly sound to all outside 
appearance may “ open out ” very poor at the saw. To 
a less extent white pine in some localities is affected in the 
same way. 
Generally, however, the ends of a log or some mark on 
its surface, such as rotten knots, “ punks,” and flows of 
pitch give indication to the practiced eye of defect beneath. 
How much to allow is then a matter of judgment based 
on mill experience. 
The following table 1 has been made up, giving the loss 
due to round center defects extending through or affecting 
the full length of a log. For four- or five-inch defects, it 
amounts to the same thing as throwing out a scantling 
having the same side as the hole has diameter. 
As stated at the start, careful mill training is the only 
safe basis for the correct culling or discounting of logs. 
Some scalers have that; some do not, and have to rely either 
1 Graves’ “ Forest Mensuration.” 
