32 Forestry Quarterly 



estry, is recorded a series of measurements on 165 white pine 

 trees cutting 894 16-foot logs. These measurements give a taper 

 of 1.62 inches per 8 feet, bark inclusive, for the merchantable 

 portion of the trees above breast height. This would indicate a 

 taper exclusive of bark of fully 1.40 inches. This is a very high 

 average for white pine and is doubtless due to the large size of 

 the trees, the average diameter being 25 inches breasthigh. It 

 is a general rule that the taper shown increases with the diameter 

 after trees have passed the pole stage. This is especially marked 

 in the case of dominant trees. 



The Baxter rule gives an allowance for taper in its scaling 

 score in the case of logs 18 feet long and over, the New Bruns- 

 wick rule for logs 27 feet long and over, and the British Columbia 

 rule for logs 50 feet long and over. The International rule al- 

 lows for an average taper of one inch per eight feet in the case 

 of all logs regardless of length. This is safely conservative for 

 all diameters and all species. 



Allowance for Shrinkage in Seasoning. A point that has been 

 overlooked by some rule makers is that the scale given should 

 refer to the amount of seasoned inch lumber which can be sawn 

 from the logs scaled. Inasmuch as logs are ordinarily scaled 

 green, it becomes necessary to allow for the shrinkage of the 

 boards in thickness and in width which accompanies the season- 

 ing. The margins of safety adopted by different mills vary con- 

 siderably, but usually run from yk to ^-inch in the width of the 

 boards and from a scant 2V to gVi^ch in the thickness. 



In computing the International Rule a sixteenth of an inch 

 was uniformly allowed for shrinkage in thickness and all fractions 

 met in measuring the widths of the boards were disregarded 

 which is equivalent to a shrinkage allowance in width of nearly 

 half an inch. 



The waste incident to sawing any log into lumber is of two 

 distinct kinds : (i) the saw kerf z.ndi (2; that lost in sqtcare- edging 

 the hoards. The deduction for saw kerf must in all cases be a 

 proportion of the area of the cross- section of the log, and hence in- 

 creases as logs increase in size in direct proportion to the square 

 of the diameter. The deduction for square-edging the boards is, 

 on the other hand, in proportion to the bark surface of the log. 

 But the bark surface of logs increases as the logs increase in size 

 in direct proportion to the increase of diameter (not squared). 

 To illustrate : a 12-inch log has ^ of the bark surface of a 48- 



