The Meastirement of Saw Logs 87 



■sawyer, the quality of the mill equipment, the width of the saw 

 kerf, the straightness of the log, and the amount of taper present. 

 No log rule could or should concern itself with the varying skill 

 of sawyers or the quality of mill equipments. It is, however, 

 quite necessary that a log rule intended for general use be adapt- 

 able to the different widths of kerf cut by saws of various thick- 

 nesses and perhaps to the varying qualities of logs in different 

 districts as regards straightness and taper. 



Variations due to varying widths of saw kerf have been shown 

 to bear a percental relation to the scale of logs of the various 

 dimensions, and a table has been given above by means of which 

 any total scale as given by the International }i Rule {i. e., rule 

 for saws cutting a >^-inch kerf), may be adapted to saws cutting 

 other widths of kerf. It remains to be shown how a standard 

 scaling score which has been computed with special reference to 

 white pine as it is logged and sawn to-day may be adapted so as 

 to be equally satisfactory for the scaling of logs of radically dif- 

 ferent taper and sawing qualities. 



That the edging waste, whether great or small, is in propor- 

 tion to the bark surfaces of logs of all diameters has been stated. 

 It is equally true that any increase or decrease in the amount of 

 merchantable lumber that may be sawn from logs because of 

 increased or decreased average taper is also directly proportional 

 to the bark surfaces of the logs concerned. The reason for this 

 will be evident if the portion of the log represented by the taper 

 be thought of as forming a ring about the cylindrical portion 

 and thus being practically proportional to the circumference. 

 These two conditions being granted it follows that any variation 

 in the sawn product of sound logs due to roughness of surface, 

 crook, or taper, must bear a percental relation to the bark surface 

 of the logs sawn. 



Fortunately a discount or a premium directly proportional to 

 the bark surface of the logs measured may be very simply added 

 to or deducted from the scale given by a rule by using a scaling 

 stick which shall measure the diameters of all logs scaled scant 

 or full as may be desired. Thus, should the necessary edging 

 waste be unusually large— due to excessive average crook or 

 roughness— the scale may be correctly discounted by using a 

 scahng stick on which the o point is placed somewhat more than 

 I inch from the i-inch graduation on the stick. Likewise should 

 the logs cut in any locality prove to saw out a larger amount of 



