688 JOURNAL OF FORESTRY 



wane nor sap in the case of most species. None of the three takes ac- 

 count of material which can be saved from the portion of the log outside 

 of these three cants, nor of waste in sawdust within the cant. All three, 

 moreover, bear a constant ratio to the true cubic volume of the log, 

 regardless of its diameter, and conversions from and to the same and 

 from one log rule to another are possible by means of simple converting 

 factors ; for it is evident, from the formulae already given, that : 



Au reel : au quart : sixieme deduit : cinquieme deduit = . 7854 : . 6168 : 

 .4284: .3948. 



Figures "au reel" may be translated into "cinquieme deduit," for 

 example, by dividing by .7854 and multiplying by .3948, etc. There 

 are many published tables based on these formulae which eliminate all 

 computations. 



Which of these log rules is used in a given case depends, seemingly, 

 on local custom, influenced by the amount of wane commonly permitted 

 and the thickness of sap of the local species. Technically trained 

 foresters generally quote figures "au reel." 



It seems odd that such unsatisfactory rules should be current, but it 

 should be remembered that under French conditions the errors involved 

 are less serious than they would be with us. French timber is relatively 

 uniform in size, wide variations in diameter are not encountered, and it 

 is simple within a given "parcelle" to compensate the errors in the rule 

 by the price paid. It is not encouraging, however, to those American 

 foresters who advocate the exclusive use of the cubic foot of log, to the 

 exclusion of the board foot, to see that France still clings to log rules 

 far inferior even to ours. Only a real need for some expression of the 

 amount of valuable product to be obtained from a log could have pre- 

 vented the "au reel" formula from long since becoming universal. 



Methods of estimating standing timber in France are far more 

 standardized than with us. The field-work is laborious. It is almost 

 always conducted by a party of four or five guards in charge of an officer 

 who may be roughly equivalent to a forest examiner. The party works 

 always together, the guards estimating or measuring diameters of every 

 tree and calling them out to the officer, who tallies. Small trees are 

 usually guessed, but a diameter tape is used freely for checking the 

 larger trees. Diameters are taken in 5-centimeter or 2-inch classes or. 

 very commonly, circumferences are recorded instead. The officer, in 

 addition to tallying, takes the heights of enough trees to prepare a 

 height curve for each "parcelle," and estimates either the form factor 

 or the average taper. The crew works back and forth across each 

 "parcelle" in strips until every tree is thus recorded. 



