NORMAL CONDITION. 



107 



to 100 years old, which could be more conveniently classed in 

 5 periods or age-classes respectively, I. 81-100, II. 61-80, 111. 

 41-60, IV. 21-40, and V. 0-20 years old ; and the area of each 

 such periodic age-class should be 400 acres. 



(2) Normal density is a relative term depending on the kind 

 of tree (according to its demand for light) and the climate, soil, 

 aspect, &c. The better the soil and the situation, the quicker 

 and the better is the growth, and the earlier and the more 

 frequently is thinning needed ; but though the number of trees 

 per acre be less, each is larger, and the total crop is bigger than 

 on poor land. The normal density in central German forests 

 varies as follows for the following kinds of trees on land of 

 good quality for each given kind of tree-crop : 



(3) Normal increment also varies greatly according to kind of 

 tree, soil, aspect, elevation, climate, &c., and differs at various 

 ages, the most rapid period of growth being usually from 

 20 to 50 years of age. 



(4) A normal distribution of the annual falls,, such as would 

 enable the timber to be most easily conveyed to the place of 

 sale or consumption, and would really provide security against 

 damage from wind, insects, fungi, &c., is hardly obtainable, and 

 in practice one has to arrange the falls as seems best in the 

 oldest and least satisfactory woods. 



