186 THE INCREMENT. 



then — 



K. = 100 (v/^' - 1 ) = l^f' C\/t^!l - l) = l-01J6percent. 



^' r+r // 4,2()0 + 8,820 10 ^ 



If any thinnings have been made during the » years, their 

 amount must be added to V, before the increment per cent, 

 is calculated. Supposing that in the above case 327 cubic feet 

 were cut between the years 60 and 70, then — 



,,,= 100(;/t260_t827_,)^,.,„,,^„^„,^ 



or 



4,260 + 327 - 3,820 ^ 200 . ^^^ , 



p, = ' — ^ X = l,82o i)er cent. 



^ 4,260 + 327 + 3,820 10 ^ 



+ 327 + 



It remains to add, that the formula for the increment 

 per cent, can be applied to height, diameter, or basal area 

 increment, as well as to volume increment. 



The results of investigations made on the Continent have 

 led to the preparation of yield tables for a number of species, 

 an abstract of which will be found in Appendix III. An 

 examination of these tables will confirm the conclusions so 

 far drawn. The tables for oak refer only to the lowlands of 

 Germany ; the returns of oak on hilly ground are somewhat 

 lower than those given in the tables. 



Section II. — Quality Increment. 



By quality increment is understood the increase in the 

 value per unit of volume. It is produced, in the first place, 

 by larger pieces of timber frequently fetching higher prices 

 per unit of measurement, and secondly by a reduction of 

 the cost of harvesting per unit of measurement. Quality 

 increment is independent of any alteration in the general 

 price of forest produce. 



