280 A MANUAL FOR NORTHERN WOODSMEN 



The remaining figures illustrate variation of form and 

 irregularity. Nos. 11 and 12, having the same diameter 

 breast high and also at the top of the logs used, are yet 

 13 per cent apart in contents, while the second pair of 

 matched trees differ by 19 per cent, of the average value 

 in each cas*e. The taper of the body of these trees is 

 regular, however; the variation is in the butt and top 

 log sections, the former being far more significant. Trees 

 Nos. 15 and 16 show some real irregularity, though noth- 

 ing extreme. Much wider departures from type than 

 any of these could in fact be chosen. 



In conclusion, a contrast will be drawn between present 

 commercial methods and the use of volume tables. In 

 the construction of these it is customary to throw out 

 swell butt and other abnormality of form, and, that 

 done, the tables derive strength from the law of averages. 

 Single trees may depart from the type and a certain 

 amount of variation goes with age, but the table, based 

 on a large number of trees and applied to large numbers, 

 if that is done in the same way the measures behind the table 

 were taken, gives results that are trustworthy within 

 reasonable limits. Present-day commercial estimates may 

 be equally correct, but that depends on a different thing 

 on the ability of the cruiser to size up each tree as 

 seen, on the basis of his training of every description. 



