Methods of Forest Organization. 65 



especially in mountain districts, produced very unequal 

 felling budgets. To overcome this inequality, Jacobi, in 

 Goettingen (1741) introduced proporfionaZ felling areas, 

 making the felling areas on poor sites permanently 

 larger. 



Similarly, v, Langen and Zanthier attempt equal 

 annual returns, without slavishly holding to the geomet- 

 ric division, only seeing to4t that the total area be cut 

 over in the predetermined rotation. 



The first attempts to introduce a regulated manage- 

 ment by making a volume division the basis is recorded 

 in the Harz mountains in 1547. This method based on 

 very crude estimates, although upon very fair forest de- 

 scription, was continued into the 18th century. 



In the last half of the 18th century all these crude 

 methods were improved and applied on extensive areas. 



In 1785 Zanthier combined area and volume division, 

 determining the felling budget on each felling area by 

 counting and estimating the trees and calculating how 

 many trees could be used annually under a sustained 

 yield management ; the area division being used only as 

 a check or means of control. 



A very considerable advance was made by Oettelt, 

 (who surveyed and regulated the Weimar forests in 

 1760) in the elaboration of details and establisliment 6f 

 proper principles for regulating the felling budget. 



In his forest description he introduces for the i5rst 

 time periodic age classes, usually six, but of imevai' 

 length: Young growth below twelve years, thicket tw^e 

 to twenty-four yea^^J, polewood twenty- four toiorty 

 years, clear timber forty to fifty, medium tim^'*' nftv to 

 seventy-five, mature timber sevent}'-five and- 



