FOREST ECONOMY. 221 



The value of the unit vokime increases, there- 

 fore, with the size of a log, yet in a decreasing 

 ratio ; if, now, the time required to produce the 

 cubic foot is put in relation, a nearer approach to 

 the profitable exploitable size may be made. 



A further improvement, designed to secure more 

 surely a sustained yield, requires that the number 

 of trees (at least the dominant) of different diam- 

 eter classes which are present be ascertained, and 

 the number which should normally exist be deter- 

 mined, when, if necessary, enough trees of the 

 higher or lower diameter class can be left, or else 

 the excess be removed, to bring the number to 

 standard. 



Whatever method of budget regulation is adopted, 

 it must never be forgotten that the approach to 

 normaHty can only be gradual, and can be secured 

 in shorter or longer time, depending on the owner's 

 interests ; in other words, while the regulation of a 

 budget is primarily based on mathematical measure- 

 ments of accretion, yield, and values, in practical 

 application it must be modified by judgment, which 

 makes allowance for changing conditions ; for forest 

 regulation only points the way, sets up an ideal 

 which in practice we may never approach closely ; 

 it gives us merely a standard, a measure, a check 

 upon our business. It may even be to the best 

 interest of the owner to defer entirely the attempt 

 at a sustained yield management, leaving it to a 

 more favorable future to regulate the budget accord- 



