32 



LOG RULES BASED ON CUBIC CONTENTS 



A caliper with a long arm to the end of which is attached a measuring wheel, is 

 vised. The wheel consists of ten spokes, each tipped with a spike, and all painted 

 black except one, which is yellow. The tips of the .spokes are 6 inches apart. The 

 yellow .spoke is weifjhted. When the wheel is run along a log, each revolution as 

 counted by the yellow spoke measures 5 feet, and the remaining spokes permit the 

 length of log to be measured to the nearest 6 inches. The measuring wheel is run 

 the length of the log, and then brought back to the center, at which point the caliper 

 measurement is taken. Allowance for bark is made by moving the caliper jaw 

 inward by a distance in inches equal to the estimated double width of bark on each 

 log separately. 



The diameter in inches is stamped on one edge of the arm, and around the base 

 of the arm are placed standard lengths running from 8 to 34 feet. Opposite each 

 length, and below each diameter, on the arm, is stamped the cubic volume of a log 

 of these dimensions. The lengths are also stamped on the movable arm. When 

 the log is calipered, the scaler reads the volume which lies opposite the proper length, 



Fig. 4. 



-Caliper scale for measuring logs in middle, outside bark, with 

 determining length of log. 



;heel for 



the diameter being indicated by the position of the movable arm after calipering the 

 log and taking off the bark correction. Defects are then deducted from the gross 

 volume, either by measuring the defective portion or by ocular estimate of the volume 

 of the defect. J. J. Fritz, Gorham, N. H., 1921. 



Note. In 1909 a commission of investigation recommended to the Maine 

 Legislature the adoption of the cubic foot as the statute rule of Maine. This was 

 not done. One lumber company, Hollingsworth & Whitney, Waterville, Maine, 

 has since 1904 used a cubic foot standard, measuring the middle diameter with cali- 

 pers, outside bark. The rule then allows \2h per cent deduction for volume of bark, 

 and gives the net cubic contents of sohd wood. The per cent of volume of bark is 

 not constant but varies with the size of tree and its age and exposure. The arbitrary 

 figure chosen simply represented the approximate average volume for the species 

 and region in question, namely, spruce and balsam in Maine. 



A converting factor for this rule has been suggested, of 185 cubic feet to 1000 

 feet B. M. This gives 5.4 board feet per cubic foot, or 45 per cent of the cubic con- 

 tents when measured at the middle. Reduced to diameter at small end, for a taper 

 of 1 inch in 8 feet, logs 18 inches in diameter would give 50 per cent of the small 



