88 THE THEORY AND PRACTICE OF WORKING PLANS 



'V = «>' — = 24, 5oo(^^) = 24,500X1.76 = 43,120 feet board mea- 

 na \ioo/ 



sure, equals annual cut. 



(c) Value and Application. — This method, promulgated by 

 Breymann in 1854, aims in common with the other " formula 

 methods " to secure an approach of the actual growing stock 

 toward the normal growing stock. However, in addition to the 

 employment of data which are difficult and subject to error in 

 irregular stands and extensive conditions (e.g., normal incre- 

 ment and average age calculations), it has the strong draw- 

 back that the adjustment of the excess or deficit in the growing 

 stock is spread over the whole rotation, whereas the exigencies 

 of the occasion usually warrant this adjustment in a fraction 

 of that time. 



The method is, therefore, of little practical value except 

 as a check upon other methods of regulating the cut. 



9. BY VOLUME.— BASED ON GROWING STOCK AND INCREMENT. 

 HEYER'S METHOD. 



(a) Description of Method. — Heyer bases his formula on 

 the following premises: 



(i) If a stand is normal, then an amount equal to the mean 

 annual increment can be cut each year so long as the three 

 requisites of normality are maintained, i.e., (a) normal growing 

 stock, {h) normal increment, and (c) normal distribution of the 

 age classes. 



(2) If normality in (a) and {b) exists, but (c) is abnormal, 

 it can be made normal if the normal increment is cut annually 

 or periodically, . and the cut-over stands immediately regen- 

 erated. 



(3) If the actual increment is less than the normal incre- 

 ment (the contrary can scarcely ever occur), then, even if the 

 growing stock is normal, only the actual, not the normal, incre- 

 ment can be cut. 



(4) If the growing stock is abnormal it can be brought 

 toward normality by either cutting less than the actual incre- 



