24 FORESTRY IN POLAND. 



this might be secured by an improved quality, though in 

 diminished quantity, and that the maximum quantity of 

 wood of the requisite quality could be secured in the period 

 named 300 years, by felling the trees at the age of 100, 

 and getting three crops of trees of that age off che ground, 

 than by letting all grow to the age of 150; while larger 

 timber required might be obtained by reserved baliveaux; 

 and arrangements might be made for the felling of such 

 of these as might be required, not only without detriment, 

 but if properly managed, with benefit to the crops then 

 growing. These are but a few of the simplest complica- 

 tions for which a director of operations prepares. 



The director or projector of operations, with the data 

 referred to before him, together with special requireaients 

 such as those just alluded to, if any such there be, deter- 

 mines what period of time is to be assigned to the crops 

 to be produced successively by the forests in technical 

 phrase, determines the regime, or if this has been pre-deter- 

 mined, determines the time to be allotted to a revolution, 

 or cycle, from sowing through growth and successive thin- 

 nings to felling and resowing again. The number of years 

 going to a complete revolution is very different under the 

 coppice wood regime and under the regime of timber forest ; 

 and under each of these it may vary within a comparatively 

 limited range, according to the kind of tree, the situation, 

 the demand, and the vigour of growth. This, then, has 

 to be determined next conditionally, at least, if not abso- 

 lutely. 



With this addition to the data an estimate is then made 

 of what is called la possibility, or of the cubic measurement 

 of the growth made year by year, or definite period of 

 years throughout the period of the revolution ; which 

 supplies a measurement of the wood, which, without 

 exceeding the yield, might be removed in the course of 

 each of these years, or periods of years. 



By withdrawing only the quantity thus determined, the 

 forest may be exploited without imperilling its sustained 



