175 MODERN FOREST ECONOMY. 



are to be subjected to such of the different thinnings or 

 fellings which have been referred to, with a statement 

 of what produce may reasonably be expected from each 

 operation, At successive stages of the work the results 

 obtained are compared with the estimates previously 

 formed of what they would be, and the programme may 

 then, if necessary, be modified. 



Some time before the close of each period the pro- 

 grammes for succeeding periods are subjected" to revision ; 

 and in view of actual results obtained, and of other con- 

 ditions which may have supervened, they also may be 

 modified, with provision for like revision, and, if necessary, 

 modification during its currency. 



Such is the tentative process by which, in the present 

 state of forest science, the sustained production of forests 

 is secured. In all this much depends on the completeness 

 and accuracy of the inventories, and of the estimates pre- 

 pared of the cubic measurements of existing trees, and 

 of what these may reasonably be expected to be at any 

 specified period in the future. It does not come within 

 the scope of my purpose here to enter upon an exposition 

 of what means are adopted in the solution of such problems. 

 The object aimed at is to procure from the forest in each 

 period by first, second, or later thinnings and final clearings 

 of different plots, material equivalent to the increase made 

 in that period by growth ; and not more than this that 

 the forest may be in no danger of being exhausted and 

 destroyed. 



Besides the sustained production of forests which it is 

 sought to secure by exploitation in accordance with Die 

 Fachwerke Method or La Methode des Compartiments, is a 

 natural reproduction of the forests exploited. 



Discussions have taken place in regard to the relative 

 advantages to be derived in this country from seeking the 

 restoration of forests by self-sown seed, and by artificial 

 planting. In the advanced forest economy of the Con- 

 tinent reliance is placed upon natural reproduction by 



