47 



should vary with the degriee of accuracy sought and the size 

 attained by the trees themselves. In very accurate surveys^ 

 differences of diameters as low as from 1 to 2 inches for 

 large trees and from ^ an inch to 1 inch for small trees is some- 

 times taken ; but such minute work is out of place in India 

 where a variation of 6 inches in diameter can usually be 

 employed with advantage. Theoretically, the height ought 

 also to he taken into account in making this classification ; 

 as height even more tban diameter is influenced by the 

 local factors of production. But this is impracticable in 

 most cases, and diameter-classes alone are sufficient. Where, 

 however, heights should be recorded, they can be estimated 

 by eye or with the aid of instruments specially constructed 

 for the purpose. Hitherto in India the classification usually 

 adopted has been the grouping together of all trees whose 

 diameters do not differ by more than 6 inches. Thus trees 

 having a diameter of 6 inches (or a girth of 1^ feet) and 

 under form one class ; those of from 6 inches to 12 inches 

 in diameter, or from Ig to 3 feet in girth, another ; those of 

 from 12 to 18 inches in diameter, or from 3 feet to 4^ feet 

 in girth, a third ; and so on. 



It would, perhaps, be more logical to classify according to the exploitable size of 

 each principal species. In most mature forests of the sort generally met with there 

 are three natural classes of stems more or less easily recognisable, viz.: — (1) exploitabte 

 trees of and above the exploitable dimensions ; (2) medinm-aged trees ranging from 

 the minimnm exploitable diameter down to, say, two-thirds of that size ; and (3) 

 yonng and suppressed stems the diameters of which are less than two-thirds of the 

 exploitable size. It is possible that the adoption of some such anifoim sjstem would 

 be advantageous. 



The enumeration of the trees.— The enumeration and mea- 

 surement of the trees is usually performed by parties 

 consisting each of one recorder and from 4 to 8 measurers, 

 the latter being provided with calipers for measuring the 

 diameters of the stems. The form of calipers in common use 

 consists of a graduated rule (A A), atone end of which is a 

 fixed arm(B B), and on and around which slides another arm 

 (0 C). To enable this arm to move freely, the hole (a, b, 

 0, d) is made oblique but in such a manner that, as soon as 

 the arm (0 C) comes in contact with the log or tree to b© 



