;32 JOURNAL OF FORESTRY 



Table 7. — Frustum Form Factors Compared by Sites. 



CHECKS ON NEW TABLES 



From these factors, tables were then prepared and checked by 

 the same methods as before. On account of the use of taper curves 

 it was, however, impossible to compute the deviation of each in- 

 dividual tree. A certain number of taper curves were by chance based 

 on but a single tree, and on these the average deviation was computed, 

 the probable error of the rather uncertain result being calculated. This 

 method probably yields conservatively high values, since such taper 

 curves more usually occur for sizes towards the upper or lower 

 limits of the tables, or in other words are based on relatively nonual 

 trees. The results are given in Table 8. 



It will be seen that the aggregate dififerences for each of the three 

 tables is under one-half of 1 per cent and may, therefore, be considered 

 satisfactory. It will also be noted that the same figures for individual 

 localities or groups do not exceed about 3 per cent. Theoretically, 

 of course, it would only be by increasing the number of site classes 



