A SUSTAIXED TIELD. 7 



quantit}' possible of produce required for the daily wants of the 

 population, as well as to guarantee an adequate supply of timber for 

 large civil and naval public works. The state forests ought, therefore, 

 to be subjected to that Regime and Exploitability, which, taking into 

 account the constituent species and the special conditions of vegetation, 

 shall guarantee the production of the most useful material. It is 

 moreover evident that as the wants of the State and of Society, which 

 is co-extensive with it, are ever changing, the state forests ought to be 

 able to satisfy for all time, within the limits of the possible, the 

 multifarious wants of the nation. It thus follows, firstly, that these 

 forests ought to be so worked that the exploitations are annual and 

 the quantity of produce the same from year to year ; and secondly, 

 that in treating and working those amongst them which are com- 

 posed of the more valuable species, there ought always to be a cer- 

 tain number of reserved trees fit for exploitation at any moment. 

 The object of maintaining this Reserved Fund of standing timber 

 is to provide against unexpected demands, like those of the navy 

 and the army in time of war. 



Such are the principles on which must be based the determina- 

 tion of the quota of the annual cuttings in state forests, principles 

 the application of which would be easy, if all these forests were 

 regular and composed of the better species, and if each one was 

 subjected to the Regime, Method of Treatment, and Rotation that 

 suited the most valuable of those species. But many of them are 

 irregular and composed chiefly of inferior species, or are exploited 

 at an age and according to a method of treatment which do not 

 obtain from them the highest sum of usefulness that they could 

 yield. Hence, it is necessary first of all to improve the actual 

 constitution of these forests, and to bring them little by little into 

 a better condition. 



To effect the transformation or improvement of a forest, there 

 is often no alternative but to neglect for some time the condition 

 of a sustained yield, in order to carry out in a successful manner 

 the cultural operations. Still this neglect of one of the funda- 

 mental principles of forest economy may prove in the end to be 

 more apparent than real ;' for, if, instead of considering the parti- 

 cular forest by itself, we take into account the production of all 

 those situated round the same centre of consumption, we shall 



