HEYER S METHOD. 327 



Subsequently it was further developed, especially by Gustav 

 Heyer, until it became the combination indicated in the above 

 heading: it is generally known as " Heyer's method." 



1. Theory of the Method. 



The theory of Heyer's method is as follows : — 



{(I.) To arrange all woods into a general working plan 

 according to periods, so that each period contains the 

 same, or approximately the same, area. The object of 

 this arrangement is, to equalise the increment during 

 the second and subsequent rotations. 



(h.) To equalise the real and normal growing stock, if any 

 difference should exist, in such manner and within such 

 time, as may be indicated in each case and approved by 

 the owner. 



(c.) To utilise the real increment, calculating the mean for 

 a series of years, plus or minus the quota of growing 

 stock determined under (^). 



It is obvious, that these objects can be realised only by a 

 complicated procedure, and even then only approximately, 

 because changes in one direction disturb the balance in 

 another. 



2. Practical Application of the MetJiod. 



{a.) The first step is to allot, by means of the table of age 

 classes, all woods to the several periods, and to equalise 

 the areas by suitable shittings, us indicated under the 

 method of periods by area ; care being taken to allot 

 the woods, as far as this is practicable, with due con- 

 sideration to sylvicultural requirements, and a proper 

 distribution of age classes. 



(&.) The real increment is placed equal to the real final 

 mean increment, for which purpose it is necessary to 

 determine the final age of each wood (which may differ 

 from the normal final age) and its probable volume at 



