Form of the Bole of the Balsam Fir. 59 



where the form factors of the sample trees are taken from stand- 

 ing trees by the formula /= {~ x 100)— <r. According to the 



measurements on these trees, however, the error due to this varia- 

 tion would be less than =b 2.5%. The figures are as follows : 



The average constant for the Balsam Fir as shown by this study 

 proves to be practically 21.9 as compared with 21 for the Norway 

 Spruce and 20 for the Scotch Pine. The variation of individual 

 trees from the average was considerable but in no case excessive. 

 The largest c for a single tree was 24.1, the smallest 19.7, indi- 

 cating a maximum error in volume determinations from form 

 factors derived by formula of less than ±6% for individual trees. 

 This error would be greater for the individual trees where the 

 middle diameter is measured in standing trees, but as it is a com- 

 pensating error it would certainly be inconsiderable where a fair 

 number of sample trees are used. 



The two trees of 65 feet height showing maximum variation 

 from the average of the 14 of that height are shown in the figure by 

 a light broken line (No. 59, <:= 23), and a light full line (No. 41, 

 c =■ 20.3) respectively. It will be seen that No. 41 is a very coni- 

 cal tree (form quotient, 63.6) while with No. 59 (form quotient, 

 72.4) qiiite the reverse is the case. This illustrates what has 

 already been said of the c rising somewhat with the rise of the 

 form quotient. I was interested to compare the volume obtained 

 by sectional measuring of 54 of the trees ranging in height from 

 59 to 69 feet with that obtained by using volume tables built on 

 the older and newer bases. The only tables available for such a 

 comparison are those prepared for the European or Norway Spruce 

 by Baur and Schiffel. Measurement by sections gave a volume of 

 874.7 cubic feet. Schiffel's tables (based on height, and diameter 



classes, and the — relationship) gave 898.7 cubic feet, or an error 



