88 TRANSACTIONS OF ROVAL SCOTTISH ARBORICULTURAL SOCIETY. 



tree-felling crews in a lumbering operation, and to use the 

 trees cut down by these crews, always observing before the 

 tree is cut down whether or not it appears to be normal and 

 obtaining the diameter breast-height measurement while it is 

 yet standing. The tables can only be expected to give satis- 

 factory results when applied to a large number of trees. Volume- 

 tables should, where possible, be checked by studies at the saw- 

 mills, which include first, scaling logs which have been marked 

 serially in the woods, and secondly, following them through the 

 mill to see what they can actually produce. If the work can 

 be done for about one hundred entire trees of different size 

 classes, a fairly accurate check on the volume-tables is obtained. 

 In measuring the contents of sample plots as a preliminary to 

 the construction of yield-tables or ascertaining the contents of 

 larger areas, the authors advocate the use of the mean sample- 

 tree method or volume-curve method, and in a later chapter 

 (page ii6) they would seem to indicate that the former method 

 is the one generally favoured in the United States. Other 

 methods they regard as being largely of academic interest. In 

 the volume-curve method, which, owing to its simplicity, setms 

 to have many points in its favour, the trees are tallied by 

 species and diameter classes. Then, according to the number of 

 trees and their range in sizes, five to seven trees distributed so 

 as to represent some of the smaller diameter classes, some of 

 the larger diameter classes, and some of the intermediate diameter 

 classes are selected. The trees are felled and measured and their 

 volumes plotted, and from the curves so derived the volume- 

 tables may be obtained of the trees of any diameter class. 



In applying the method of stem analysis to a large number of 

 trees, the following method is approved of by the authors, 

 because of its being simpler in application, and likely to be 

 more generally useful than the laborious methods hitherto 

 used : — 



"A large number of diameter growths are taken at specified 

 heights above the ground on trees (in woods of different 

 ages) belonging to the same crown classes, from which 

 curves are drawn to show the aggregate growth in 

 diameter by decades at each of the specified heights. 

 From these curves the dimensions of an ideal tree, the 

 average of the class are determined, and the volume of 

 the ideal tree obtained." 



