FORMULA FOR BOARD-FOOT RULES 35 



The rule gives just 50 per cent of the total cubic contents of logs 

 in board feet. This is equivalent to 6 board feet per cubic foot. This 

 rule is extensively used for imported hardwood logs. The contents 

 of logs in cubic feet is found by dividing bv 144 instead of 12. 



In practice, fractional inches resulting from the fifth girth are dropped as follows, 



e-g-, 



Girth, 50, 51 or 52 inches Square, 10 by 10 inches 

 53, 54 inches 11 by 10 inches 



55, 56, 57 inches 11 by 11 inches 



58, 59 inches 12 by 11 inches, etc. 



Square of Two-thirds Rule. Synonyms: St. Louis Hardwood, 

 Two-Thirds, Tennessee River, Lehigh, Miner. This rule is derived from 

 the Two-thirds Rule by multiplying the cubic scale by 12. The rule 

 is used for hardwood logs in the Middle States, and for pine to some 

 extent in the South Atlantic States, and is frequently erroneously 

 applied to the small-end diameter of the log. 



Cumberland River Rule. Synonyms: Evansville, Third and Fifth. 

 This rule resembles the Square of Two-Thirds Rule, in that one-third 

 of the diameter is deducted and the remainder squared. But it differs, in 

 that one-fifth of the volume of the squared stick is then subtracted for 

 saw kerf, and the remainder converted into board feet. The rule is 

 always applied to the small end of the log except for long logs, when 

 the diameter at middle point is taken. This rule is used on the Missis- 

 sippi Valley and its tributaries, for hardwood logs. 



Square of Three-fourths Rule. Synonyms: Portland, Noble & 

 Cooley, Cook, Crooked River, Lumberman's. In this rule, one-fourth 

 is deducted from the diameter at small end, and the squared timber 

 expressed in board feet. The rule was formerly used in New England 

 but is now obsolete. 



Vermont Rule. This rule is derived from the Inscribed Square 

 Rule by multiplying the values by 12. It is the legal standard of the 

 State of Vermont. The contents of a 12-foot log may be calculated by 

 a rule of thumb, by multiplying the average diameter of the top of the 

 log inside bark, in inches, by half such diameter in inches. The rule is 

 not extensively used even in Vermont, being supplanted by others, 

 notably the New Hampshire or Blodgett Rule. 



37. Formula for Board-foot Rules Based on Cubic Contents. 

 Any board-foot log rule the values for which are obtained by deducting 

 the same per cent from the cubic contents of logs of all sizes, may be 

 expressed by the formula 



Board feet = (1 - C)^ X -^ X L, 

 4 144 ' 



