22 FORESTRY IN POLAND. 



Let it be supposed that it is virgin forest which is to be 

 exploited it is ascertained, by survey and inspection, of 

 what kinds of trees it is composed ; what age, or differ- 

 ent ages, the different kinds of trees are ; in what condi- 

 tion they are ; what measure of vigour of growth they 

 manifest, and what are the promises, in regard to this 

 measure of vigour being maintained or increased in coming 

 years, supplied by the nature of the soil and the situation 

 of the trees. Thus a general idea of the peuplement of the 

 forest is obtained. By another series of observations which 

 may have previously been made in connection with, or in 

 preparation for, the exploitation of other woods, or, which 

 if not previously made, must be made now, it must be ascer- 

 tained in regard to the kind or different kinds of trees of 

 which the peuplement of the forest consists what increase 

 of cubic contents these make in the course of a year, or of 

 any definite number of years say five or ten at all 

 stages of growth, from that of a sapling to that of an old 

 tree beginning to decay ; and in connection with this, by 

 deduction from data thus obtained or by separate observa- 

 tion, it must be ascertained to what age and magnitude 

 the kind of tree growing there may attain without decay ; 

 at what age the annual increase becomes so diminished 

 that a greater production of wood in a given period of 

 considerable duration may be obtained by felling and 

 raising a new crop, than by allowing the trees to go on 

 growing ; at what age of growth the wood is of best quality 

 for the purpose for which it is required ; and at what age 

 a maximum of wood of such superior quality would be 

 secured by then felling the tree. 



In illustration of what may thus be learned I may 

 adduce a hypothetical case. Suppose, what is likely to be 

 the case, that a tree in its growth makes an increasing 

 increment of cubic contents year by year, and decade by 

 decade, up to the age of sixty, making more wood between 

 10 and 20 than between 1 and 10, more between 20 and 

 30 than between 10 and 20, and so on continuously, more 

 between 50 and 60 than between 40 and 50 : it may be 



