340 JOURNAL OF FORESTRY 



curves of a volume table. One of the minor perplexities in this 

 work is the selection of a scale which will not crowd together the smaller 

 measurements and yet which will not unduly expand the larger. 

 Figure 1, A and B, represents the two sets of curves (by diameter 

 and height classes) read from a U. S. Forest Service volume table 

 for Douglas fir. In figure 1-A the values are plotted exactly as they 

 stand in the table, while in figure 1-B certain minor irregularities, 

 which appear as the result of a failure to completely harmonize the 

 curves, have been smoothed out. The charts are, of course, on a 

 reduced scale to permit reproduction, but it is easily evident that the 

 graph would have to be several times larger in order to give any 

 facility in handling the lower curves of figure 1-B. This means a 

 sheet which is decidedly unwieldy, and which affords much more 

 space than is needed for the upper curves. Figure 2, A and B, repre- 

 sents the same curves on logarithmic paper. It will be noted that 

 the lower curves here have more space, if anything, than the upper, 

 and it is evident that a much smaller sheet can be used. In fact, in 

 this particular case to obtain an equally wide spacing between the 

 closest curves, figure 1-B would need to be some six times as large 

 as figure 2-B. 



A second advantage is connected with the number of digits which 

 can be read. Principally as a result of the large-size graphs necessary 

 with ordinary cross-section paper to secure proper curve spacing in 

 the lower diameters, it is all too common to find volume tables in 

 which an absurd degree of accuracy is apparently indicated. Four 

 significant figures implying an accuracy to within 1/100 of 1 

 per cent are all too common. Such an absurdity is almost im- 

 possible with logarithmic paper. The space between 91 and 92 and 

 between 9100 and 9200 are identical, and the temptation to unjusti- 

 fied refinement disappears. An opportunity to go into unnecessary 

 decimals in the case of the smallest trees is of course ofifered, but 

 this temptation is more easily resisted. The contraction of the 

 horizontal scale in the higher values is also entirely consistent with 

 the accuracy to which measurements can be taken. The diameter of 

 large trees cannot be as accurately measured as of small, and the 

 lessened refinement possible in plotting is logical and desirable. 



A third point of interest is involved in the shape of the resulting 

 curves. If a straight edge is laid on the curves of figure 2-A, it will 

 be observed that all of them are strikingly close to straight lines 



