56 



University of California Publications in Agricultural Sciences [Vol.3 



strument is required as in the last case, save that a slightly larger 

 range of diameters is needed and a fixed adjustment for a definite size 

 is not adequate. 



Many Pacific coast volume tables are based on diameter, height, 

 and taper. While the first two factors are measured, at least occasion- 

 ally, the last is usually a matter of guesswork entirely. The instru- 

 ment needed to strengthen this part of the work is a dendrometer 

 possessing the qualities above mentioned, and in addition one which 

 works independently of distance, since both horizontal distances and 

 heights will usually be but roughly approximated. 



In many scientific studies of growth on permanent sample plots in 

 this country periodic measurements of diameters breast-high and 



^>*44/f/ss»r 



^fjdn>q/y>>r*r 



z. f J-/ne of $fqb t 



%^ /n dtrect /./ ne. of S/yAf 





Fig. 1 



heights are being secured, and growth in volume is being calculated 

 from these data by means of a single volume table for each species. 

 As a result, whatever growth results from a change in tree form is 

 being neglected. A dendrometer is needed of considerable precision, 

 but not necessarily so portable or rapid in action as in the previous 

 cases. Its range in most cases need not be great, since the more 

 important growth problems are connected with second-growth timber 

 or, at least, with trees below a certain diameter limit. 



Schiffel's formula for obtaining volume has not been sufficiently 

 tested for most American species, but it is regarded as probably having 

 a high value in many cases. It requires a measurement of diameter 

 at a point half way up the bole, and hence a dendrometer. The 

 qualifications of a satisfactory instrument will naturally depend on 

 the character of the work being done. 



All these instances indicate that it is not due to the absence of a 

 real need that dendrometers are practically unknown in America. It 

 seems obvious, rather, that no existing type satisfies the conditions 



