88 THE THEORY AND PRACTICE OF WORKING PLANS 



y — ny — = 24,5001 -—) =24,500X1.76 = 43,120 feet board mea- 

 na \ioo/ 



sure, equals annual cut. 



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

 Bre\TTiann 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 

 emplo^Tuent 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, ih) normal increment, and (c) normal distribution of the 

 age classes. 



(2) If normality in (a) and (&) 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- 



