THE PROBLEM OF MAKING VOLUME TABLES 583 



Smalian Formula method, and since it is based on a law of form, it 

 would probably require less trees to get a smooth table than the con- 

 ventional method. 



In this country, it appears, however, that we are going to want our 

 volume tables in the board foot unit for some time to come, and board 

 foot measure does not lend itself easily to formulae or to the ordinary 

 form factors which are useful short cuts in making cubic measure 

 volume tables. My discussion, therefore, is limited to preparation of 

 volume tables expressed in the board foot unit. 



Recently, in several articles, Bruce has explained a method, the 

 frustum form factor method, of constructing a table which promises 

 to give good results from fewer trees. In brief, this method consists 

 of determining the ratio between the scaled contents of a tree and a 

 frustum of a cone of equivalent basal and top diameter and height. 

 The ratios thus secured are averaged, — and they seem to run very 

 uniformly even for a small number of trees — and then applied to the 

 base table of frustums of cones of all needed dimensions. The final 

 form of the volume table is identical with the conventional table. 

 Several of the districts, perhaps all of them, have tried out this short- 

 cut method and reported favorably upon it. I think there is a field 

 for Research in investigating it still further. It is particularly im- 

 portant to determine whether these factors are constant for virgin 

 and overmature timber, where the laws of form are less regular than 

 with young timber. In Europe stem form factors and timber form 

 factors have been used in making tables, but in European forests form 

 factors are perhaps more regular than in our virgin timber, and cubic 

 measure lends itself to form factor expression more easily than does 

 the board foot. 



The use of the present frustum form factor method in constructing 

 volume tables with varying top diameters involves an exceedingly 

 complicated base table of frustum volumes and one which is not 

 universally applicable. To overcome this difficulty, Weitknecht has 

 proposed that the scaled contents of the merchantable part of the tree 

 be compared to the contents not of a frustum, but of a full cone whose 

 height is equal to the total height of the tree. The base table will 

 show the volumes of entire cones expressed in board feet and the 

 factor will be a timber form factor instead of a frustum form factor. 

 This would make it possible to estimate by total height, a procedure 

 that I have said before has points of superiority over merchantable 



