DISCOUNTING FOR DEFECT IN CORD MEASURE 133 



applied to peeled wood by subtracting diameter of bark. The old 

 Partridge rule used at Winchendon, Mass., computes the stacked volume 



of the log as (D 2 )— with D = diameter in feet. Each " cubic foot " 



by this rule is xks cord. The rule is thus based on stacked contents, 

 and fractional cords are reduced to decimals by the divisor 128; e.g., 

 64 " feet " would give .5 cord. 



To simplify this process the cordwood caliper rule known as the 

 Humphrey Caliper 1 Rule, was divided into tut of a cord; i.e., instead 

 of measuring a stacked cubic foot the unit or xtt C01 "d equaled 1.28 

 stacked cubic feet. The scale stick for this rule was not marked off 

 in inches, but for each standard length of stick the graduations repre- 

 senting diameter were placed at the points which gave logs measuring 

 a certain even volume (§ 80). Hence no fractional stacked feet were 

 shown. 



Since oy either rule, the cubic contents of a cord is given as 100.5 

 cubic feet, the Humphrey Rule by using the decimal system expressed 



the contents as — -^r — within an error of but 0.5 per cent. The values 



of the rule thus correspond with those given for cubic contents of cylin- 

 ders, but pointed off for two decimals. 



If we accept the standard of 100 solid cubic feet of wood as the 

 maximum contents of a cord, the Humphrey Caliper Rule measures 

 wood of any character or degree of straightness, surface, roughness, 

 length or diameter not only by a uniform standard of cubic contents 

 (as does the Partridge Rule) but directly in cubic feet, or in standard 

 cubic contents. 



This rule therefore offers a double advantage. It is not only a cubic- 

 foot standard, which is desirable for all scientific measurements of volume 

 and growth, but it serves to standardize cord measure as well, on the 

 basis of solid rather than stacked contents. The limitations in the 

 use of the rule are the same as those of all caliper rules (§ 84). It can- 

 not be applied to wood in the stack but only to pieces measured singly. 

 Scale sticks made up for these values would enable measurements of 

 cubic contents to be made directly for logs or trees to be used for vol- 

 ume tables or other scientific purposes and would do away with cal- 

 culation of cubic contents. This rule is used as the principal com- 

 mercial standard in the vicinity of Keene, New Hampshire. It can be 

 made up by anyone on the basis of diameter by applying the cubic 

 contents of cylinders given in Table LXXVII, Appendix C. 



112. Discounting for Defect in Cord Measure. Pulpwood must be spund and 

 free from rot or defective knots. Where logs of 8, 12 or 16 feet are measured by 

 1 Invented by John Humphrey, Keene, N. H. 



