Normal Stock Methods. 109 
a. Based 
upon the normal forest idea, a number of methods were 
elaborated which, because of their employing a mathe- 
matical formula for the determination of the felling 
budget, are known as the formula methods; they are, in- 
deed modified rational volume divisions. Hundeshagen 
has the merit of having clearly explained the basis of 
these methods and himself developed a formula, of the 
correctness of which he was so convinced as to designate 
his method as “the rational” one. Two other formule 
were brought into the world by Koenig (1838-1851), but 
the credit of the most complete elaboration both of the 
principles of the normal forest idea and of its practical 
application belongs to Carl Heyer. The principles of 
his method are briefly: First determine upon the period 
of regulation, during which the abnormal forest is to be 
brought nearly to normal conditions; the length of this 
period to be determined with due regard to the financial 
requirements or ability of the owner and to the condi- 
tions of the forest. The actual stock on hand is then 
determined and the increment which will take place dur- 
ing this period added. Deducting what has been caleu- 
lated as the proper normal stock requisite for a sus- 
tained yield management, the balance is available for 
felling budgets which may be utilized in annual or 
periodic instalments during the period of regulation. A 
working plan is provided which takes care of securing an 
orderly progress of fellings and proper location of age 
classes, to be revised every ten years. 
Although this is undoubtedly the most rational 
method yet devised, it has remained largely unused, and 
8 
Carl Heyer (Felling budget=I,+ 
