552 JOURNAL OF FORESTRY 



The fixed top cutting limit is seen to be slightly but consistently su- 

 perior, yet the differences are small and practical considerations again 

 may determine our choice. For certain work, such as permanent 

 sample plot measurements, it is of prime importance that the height 

 measurement be taken by a method of great precision, so as to permit 

 detection of small increases in height. Since it is difficult to be sure of 

 the exact point at which to sight the hypsometer in measuring mer- 

 chantable heights, the total height has been and probably will continue 

 to be preferred for such work. For the occasional volume table ex- 

 pressed in cubic feet, also, this basis is almost forced upon us. In 

 routine timber estimating, however, particularly in the very tall timber 

 of the west coast and the Inland Empire, it is sometimes nearly impos- 

 sible and often very difficult to see the extreme tip of the tree. The 

 estimator often wants, moreover, in addition to his volume estimate, 

 figures on the actual merchantable or used length of the trees, or the 

 total number of logs in a stand, or the log run. Such figures are col- 

 lected automatically where merchantable or used height tables are em- 

 ployed. For such cases, then, total height will not do, and it remains 

 to be considered whether heights are to be measured to a fixed top 

 cutting limit or to a limit varying with the logging practice of the region. 



The case for the latter has been strongly presented by Chapman,^ 

 who uses two main arguments. He points out that since the importance 

 of the top cutting limit is far greater from the standpoint of a height 

 index than of a utilization index, surprisingly grave errors will result 

 if a cruiser estimates heights to the used top and then applies a fixetJ 

 top volume table. This, of course, works both ways, and only supports 

 the theory of used top volume tables if his second contention is also 

 true, namely, that there exists "a natural tendency of estimators . . . 

 to tally to the point which represents used length." 



One of the species mentioned by Chapman as being characteristically 

 cut to a variable top is the western yellow pine. Some twelve volume 

 tables of the modern type have been prepared by the Forest Service 

 for this species. In five of these the fixed top cutting limit was adopt- 

 ed, while in the other seven a range was used as shown in the following 

 table : 



*"The Effect of Top Diameters in Construction and Application of Volume 

 Tables Based on Log Lengths," by H. H. Chapman, Proc. Soc. Amer. For., 

 XI:2:221flf. 



