724 jouRNAi, OF fore;stry 



In the above tabulation each locaHty was in general kept separate, 

 though in cases where only a sniall number of tree measurements 

 had been used on a single Forest, no subdivision of this Forest was at- 

 tempted. Included therein are, moreover, three groups (identified by 

 parentheses) which were perhaps not used in the original prepara- 

 tion of the table, they check, however, as well as others that were used, 

 and are an unimportant factor in the totals. The total number of trees 

 does not exactly correspond with the figure printed on Form 8T4nn, 

 due to the fact that it was not always possible to tell just which data 

 sheets had been discarded, but the difference is too small to be ma- 

 terial. 



It will be seen that the total aggregate difference of 0.19 per cent 

 is beyond criticism but that the corresponding average deviation of 

 16.0 per cent is suspiciously high. The reason for this is evident on ex- 

 amining the detailed figures, for even the aggregate differences of in- 

 dividual groups of trees are absurdly large. Some of these groups are, 

 of course, too small to be very significant, but there is no excuse for 

 a difference of over 7 per cent in 468 trees, or of 54 per cent in 50 

 trees. It is obvious that the table has combined very diverse values in- 

 to an average which is of little meaning, for in practical use, it is not 

 customary to combine tree measurements from widely separated For- 

 ests, and hence the compensation of errors which appears in Table 1 

 cannot be counted on. 



The question arises whether the difference which is so obvious be- 

 tween the different groups is due to form. The next most probable 

 alternative is a difference in top utilization. An investigation of the two 

 largest groups disclosed decided variations in the latter and such as 

 might account largely for the discrepancy between the two ag- 

 gregate deviations. Varying top cutting limits, therefore, are probably 

 one cause of the unsatisfactory results of Table 1, but it is possible that 

 variations in form also had an influence. That this was the case is 

 proved by the results hereinafter to be described. 



• THE BASIC DATA FOR THE STUDY 



Further progress now seemed to necessitate the preparation of sev 

 eral different volume tables, perhaps using data combined in differ- 

 ent ways. In addition to the basic data already described there were 

 available for this study about 800 tree measurements taken under the 

 direction of Dr. E. P. Meinecke, of the U. S. Bureau of Plant 



