DISCUSSION OF LOG RULES. 



11 



in lumber of any kind with a set of tables that can implicitly be 

 relied upon for correctness by both buyer and seller, and to do so 

 I have spared no pains nor expense to render them perfect; and it 

 is to be hoped that hereafter these will be preferred to the palpably 

 erroneous tables which have hitherto been in use. If there is any 

 truth in mathematics or dependence to be placed in the estimates 

 given in diagrams, there cannot remain a particle of doubt of the 

 accuracy of the results here given." 



This log rule gives practically the same results as does the Spaulding. 

 It is not as carefully prepared, however, since the values given are not 

 as consistent with the underlying principles of the rule. A graphic 



6000 



0500 



900 



tO 12 14 16 18 2O 22 



AREA INSIDE BARK SMALL END-SO. FT 



FIG. 3. A graphic analysis of the Scribner Log Rule, based upon area in square 

 feet inside bark at small end of logs. This diagram shows the following: (a) Top 

 curve, total contents in board feet of logs of different diameters 16' long, with no 

 allowance made for taper. (&) Curve "k," volume in board feet remaining after 

 18% of the total volume has been allowed for sawdust (this allowance is about right 

 for \" saw-kerf), (c) Curve passing through origin and drawn parallel to bottom 

 curve, (d) Bottom curve located by plotting volume in board feet for 16' logs of even 

 inches in diameter inside bark as given by the Scribner Log Rule. The formula 

 indicated by this analysis is as follows: (.048Z> 2 3)I/ = B. M. = volume in board 

 feet. This formula is almost identical with the one obtained for the Spaulding Log 

 Rule. It does not apply, however, to diameters below 14" or above 75". No formula 

 can be written for the Scribner Log Rule that will fit all values given, due to the 

 inconsistency of the individual values of the rule. 



analysis of it is given in Fig. 3, which shows the fundamental principles 

 upon which it is based, and which are the same as for the Spaulding 

 rule. The formula indicated by the analysis shown in Fig. 3 is 

 (.048D 2 3)L = B. M. = volume in board feet, which is practically the 

 same as for the Spaulding Log Rule, the only difference being in the 

 constant "3". Fi^. 4 shows how closely this formula fits the rule. 



