MEASUREMENT OF TIMBER 201 



is going on. When the calliper man finds a tree whose 

 diameter is exactly 6, 7, 8, or 9 inches, or whatever the 

 diameter of the inch-class may be, he calls out to the hooker, 

 who examines the tree, and if it seems a good average one it 

 can be marked at once, so that it will be easily found again. 

 A good way to mark it is to pin a large piece of white paper 

 to it. When a sample tree has thus been found, the booker 

 places a cross in his note-book against that inch- class to 

 indicate that no further sample tree is required for that class. 

 By doing this carefully, sample trees will have been found 

 for each inch-class by the time that all the trees have been 

 measured. If this method is carried out it is necessary to 

 ascertain the average height of the inch-classes beforehand 

 with an instrument. Then as each sample tree is found its 

 height is taken and compared with the average. If very 

 different in height the tree is not chosen. 



The sample trees are cut down and each is carefully measured 

 by the ordinary square-of-quarter-girth method as already 

 described. Bark allowance can be made at the same time. 

 The volume of each inch-class is now worked out by multiply- 

 ing the volume of the sample tree by the number of trees in 

 the inch-class, and the volume of the whole wood is ascertained 

 by adding together the volume of all the inch-classes. 



The following example illustrates the method. The figures 

 are those obtained on one acre of larch wood aged sixty-five 

 years in the Tintern woods and were measured by the School 

 of Forestry, Forest of Dean. The wood was afterwards cut 

 and the measured felled timber came to practically the same 

 amount. 



The following are the details of the sample trees felled, 

 and measured by square-of-quarter-girth with the usual bark 

 allowance. The trees were measured down to 3 inches diameter 

 at the thin end. 



It will be noticed that the trees were somewhat thin, but 

 were of great length. 



