70 Germany. 



inequality, Jacobi, in Goettingen (1741) introduced 

 proportional felling areas, making the felling areas on 

 poor sites permanently larger. 



Similarly, v. Langen and Zanthier attempt to secure 

 equal annual returns without slavishly holding to the 

 geometric division, merely making sure 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 

 from the Harz mountains in 1547. This method, 

 based on very crude estimates although upon very fair 

 forest description, 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 di- 

 vision, determining the felling budget on each felling 

 area by counting and estimating the trees and calcu- 

 lating 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 establishment 

 of proper principles for regulating the felling budget. 



In his forest description he introduces for the first 

 time periodic age classes, usually six, but of uneven 

 length: Young growth, below twelve years; thicket, 

 twelve to twenty-four years; polewood, twenty-four 

 to forty years; clear timber, forty to fifty; medium 

 timber, fifty to seventy-five; mature timber, seventy- 

 five years and over. 



