316 DETERMINATION OF THE YIELD. 



I. period = 36*00 acres. 



II. - 34-02 



III. = 27-30 



IV. = 29-05 

 V. = 33-78 



Total = 160-15 

 Mean periodic area= 32*03 



b. Merits of the Method. 



The method has this advantage over the method by area, 

 that it gives during the first rotation equal, or approximately 

 equal, periodic returns; it considers the interests of the present 

 generation more fully. On the other hand, the estimate of the 

 future returns is more or less problematic, so that the equali- 

 zation of the returns for a whole rotation ahead is a very 

 uncertain operation. It shares with the method by area the 

 disadvantage that a proper grouping of age classes is generally 

 beset by difficulties. Again, it drags a surplus of growing 

 stock over a whole rotation. 



Whereas the method by area establishes the normal state of 

 the forest within one rotation, the method by volume takes 

 several rotations to accomplish this. 



As regards its financial aspect, it stands on the same footing 

 as the method by area. 



3. The Method of Periods by Area and Volume combined. 



The woods of a forest are so allotted to the several periods 

 of a rotation, that each contains the same area and yields the 

 same, or approximately the same, volume. 



The equalization of the periodic areas and returns is effected 

 either by adding columns for the volume to the general 

 working plan used for the method by area, or by adding 

 columns showing the reduced areas to the general working 

 plan used for the method by volume. Shiftings are made until 

 both area and yield are the same, or approximately the same, 

 in each period. 



