Forvi of the Bole of the Balsam Fir. 6 1 



same at breast-high and at the middle point of the bole, and are 

 of the same height they cannot vary greatly in vohime. This third 

 factor, the relative diameter at the middle point, is the basic 

 principle which separates these tables from all others. It is this 

 which makes the same table applicable to stands of all ages and 

 grown under all silvicultural conditions, notwithstanding the fact 

 that changes in environment and development may produce 

 changes in the form of the bole which result in variations of over 

 20% in the cubic content of stems having the same height and 

 breast-high diameter, and grown side by side in the same stand. 

 Some of the trees from various causes or combinations of causes 

 are in any stand much more cylindrical than their neighbors. If, 

 however, we look for the volumes of two trees, varying essential- 

 ly in form of bole in Schiffel's tables the larger diameter at the 

 middle point places the more cylindrical tree in a very different 

 table from that used for its conical neighbor. 



Another point in this connection might bear repeating and ad- 

 dition. So far as the constant has been determined for the dif- 

 ferent species it has been shown to be remarkably uniform. That 

 for the Scotch Pine in Europe is 20, Norway Spruce 21, 

 European Beech 22 to 23, Balsam Fir, so far as examined, 21.9. 

 I have also examined a few trees of Hemlock, Tamarack, Red 

 Spruce, White Cedar, and Pitch Pine (/*. rigida) all of which in- 

 dicated a constant not greatly differing from that of the Norway 

 Spruce. 37 trees of White Pine, averaging 260 years old and 

 about 143 ft. in height gave by far the highest result, viz., 24. 

 This high constant in this case was due to the excessive enlarge- 

 ment at the base of the boles shown by the trees studied, and is 

 probably an extreme case. In any event, the constant being 

 known, it is a simple matter to determine the per cent, which 

 must be added to or subtracted from the volume read from the 

 tables for any given species to get the correct content. 



The enlargement of the tables so as to provide for all combina- 

 tions of dimensions which may be met in field work with our 

 eastern conifers is a large task. My studies in interpolation by 

 means of curves where necessary has led me to believe that it is 

 possible that a solution of the problem lies in this direction, very 

 satisfactory results having been obtained in interpolating for the 

 Red Spruce and the White Pine, 



J. F. C. 



