97 



and many others. The more accurate methods employed in 

 European forestry are not intended for such forests, and it is 

 a question whether they can be made use of except where 

 the whole crop is saleable. 



The simplest and most satisfactory of these European 

 methods is the one which was first introduced into France 

 in 18S3, and it has since then been applied to a large 

 number of hill forests, treated under the selection system. 

 This method is based on considerations similar to thnse which" 

 influence the determination of the possibility of regular high 

 forest, composed of properly graduated series of crops of all 

 ages up to the number of years comprised in the normal 

 rotation. These crops may be classed under one of three 

 groups, each of which would obviously occupy one-third 

 of the total area, viz,: — 



I. — Full-aged crops, of which the ages will range 

 downwards to two-thirds of the total number 

 of years comprised in the exploitable age. 



II. — Medium-aged crops, of which the ages will range 

 from wto-thirds to one-third the number of 

 years in that age. 



III. — Young crops, aged less than one-third the num- 

 ber of years in the exploitable" age. 



It is evident that, iu a regular high fores-t so stocked and 

 in which the elements of production are everywhere identi- 

 cal, a sustained yield will be assured if each group is in its 

 turn regenerated during one-third the number of years in 

 the exploitable age. The annual yield can, therefore, be 

 determined by dividing the volume of material contained in 

 the full-aged crops, with the addition, if possible, of its 

 increment up to the time of felling, by the number of years 

 in one-third of the exploitable age. When a forest does not 

 contain crops of all ages covering equal areas, it may be 

 necessary to make transfers from one group to another, so 

 that the areas to be exploited in equal intervals may be 

 equalised. 



If for a regular be substituted a selection-worked high 

 forest, it is still possible, notwithstanding the apparent 

 irregularity of the latter, to distinguish in it these three 

 groups, namely, of full-aged, medium-aged and young 

 crops. But the areas respectively stocked with these three 



