A NEW METHOD OF CONSTRUCTING VOLUME 



TABLES. 



By Donald Bruce;. 



To the average forester of technical training a voUime table 

 is an essential to timber estimating. Upon its accuracy depends, 

 to a large degree the accuracy of his work, and in its absence 

 he is often nearly helpless. Fortunately, there are now published, 

 chiefly by the U. S. Forest Service, quite usable tables of this 

 sort for practically every species of tree of commercial import- 

 ance. 



It is well recognized, however, that even the most carefully 

 compiled table is of assured accuracy only when applied to timber 

 similar to that from which the measurements used in the con- 

 struction of that table were taken. A slight variation in site, 

 climate, or age or form of stand, may induce a considerable de- 

 viation from the tabulated figures. Yet in practical work it is 

 exceptional to be able to find a table that does apply exactly to 

 the stand which must be estimated. Furthermore, the construc- 

 tion of one to suit the occasion is almost of prohibitive expense 

 on account of the large number of tree measurements neces- 

 sary for really satisfactory results. 



Under such conditions the would-be estimator of technical train- 

 ing has been forced to choose between two evils. He had either 

 to use a table constructed carefully for other conditions, but of 

 dubious accuracy in the case before him, or to roughly construct 

 for himself a local table based on entirely inadequate data. In 

 the former case he has, perhaps, checked his table by taking 

 a few local measurements, but a completely satisfactory check 

 would demand measurements almost sufficient in number for the 

 compilation of a new table. Yet this has been probably the least 

 objectionable method available. 



A third method has recently occurred to the writer which has 

 several advantages over either of the alternatives mentioned above. 

 It involves the use of what may be termed, for lack of a bet- 

 ter term, the frustrum form factor. This may be defined as the 



