INTRODUCTORY. 173 



series of age gradations so arranged, that at all times, when 

 cuttings are to be made, woods of the normal age are available 

 in such a position, that no obstacles to their cutting exist. 



The normal growing stock is that, which is present in a forest, 

 in which the age gradations are normally arranged and show 

 the normal increment. It can, however, also be present (in 

 quantity) in an abnormal forest, if the deficiency of some 

 woods is made good by a surplus in others. 



For the strictly annual working and the clear cutting system, 

 a forest is, therefore, normal, if it consists of a series of fully 

 stocked woods equal in number to the number of years in the 

 rotation and of the same extent, so that each year a wood of 

 the normal age can be cut, and that the returns are equal, at 

 any rate in quantity if not in value. 



From a financial point of view, the further condition must 

 be added, that there should be no woods in the forest, 

 the current per cent, of which has sunk below the general 

 per cent, jj (see p. 165). 



In accordance with these definitions, the following matters 

 demand special attention : — 



(1.) The increment. 



(2.) The rotation, or the norma! age at which woods should 

 be cut over. 



(3.) The normal age classes. 



(4.) The normal growing stock. 



(5.) The normal yield. 



(6.) The relations which exist between increment, growing 

 stock and yield. 



(7.) The real forest compared with the normal forest. 



