— 210 — 



so we may evidently determine that the form-height, hf^ depends upon 

 the form of a tree bole, i.e. that the breast-height form factor may be 

 considered as a true expression of the form of the tree bole. Still, it is 

 questionable to apply the conclusion to the mean hf, for a given height of 

 a given species because there are various forms of tree for a given height. 

 In this case the breast-height form factor, means merely the coefficient 

 for estimating contents of treejboles by means of g„,h. 



C. Form Factor 



From the previous part it will be evidently seen that the volume of 

 the tree bole may be calculated by the formula : 



26 



./ 



,, 2a'h — — ; — r- Ah 



when we know the equation of the outline curve on the longitudinal 

 section of the tree bole as 



a' X 



From the formula of Vs, it will be suggested that the variation of 

 Vs for different heights, and diameters at breast-height, may be expressed 

 thus : — 



Vs=L g^e 

 where L, L„ and L2 are the constants depending upon the species and 

 " form-quotients." 

 So we get 





/.=LJ-e '^ 



p 

 h 



Now if we assume that for given species the breast-height form 

 factor varies as the height of tree only and is independed of the " form- 

 quotient," then fs is the mono-valued function of h. But such an assump- 

 tion is a very crude approximation. Yet the practical estimation of the 

 contents of a standing tree in a stand sometimes demands such a crude 

 approximation, and to this end, I constructed form factor table. 



The data are as follows: — 



