67 



1 he figures obtained for the volumes should he checked by coo- 

 structing similar curves with the known numbers of trees, basal 

 areas and heights, and obtaining by interpolation the corresponding 

 figures for tbe other ages. The complete figures obtained for each 

 series should then be compared : wherever discrepancies are found 

 corrections can be easily made. Such a check for the volumes is 

 best obtained by comparison with the figures obtained for the basal 

 areas and heights, the products of which, multiplied by the respec- 

 tive form-factors, will furnish another series of volume figures. 

 The form-factors used may be obtained at the same time as the 

 other information. 



The accuracy of yield tables is always more or less nneertain, 

 owing to the difficulty of selecting the experimental crops so that 

 they may be exact counterparts of each other at their own respec- 

 tive ages. The necessary correspondence is best secured by 

 careful and detailed stem aualyses in the older crops, in order that 

 the heights of the dominant stems at earlier periods may be more 

 or less exactly ascertained. The experimental crops for these 

 earlier periods should then be so selected that their average heights 

 correspond with the figures thus deduced. 



GoTeromtDt of fnaia Central Printing Office.-Xo, lOi* E. t A.— 16-8-93.-I.O0O.— J. K.tJ. DeC. 



