532 Forestry Quarterly 



feet is attained in 20 years the average ring width of the mean 

 stem is kept at Ve cm., i.e., the diameter increases at Vs cm. 

 (1 inch in 7 years), then to produce stems of the five classes 

 requires the following time : 



On poorer soils, where the average ring width is only Vs cm. 

 (1 inch diameter in 10 years), and where the 5 or 6 size classes are 

 attained in the noted times, the annual value increment per cents 

 in the two cases were : 



To show the method of presentation in full, we translate the 

 tabulation for the second district in detail : 



The figures are significant in showing the impropriety of gen- 

 eralizing, if economic resiilts are considered. While normal 

 yield tables have their value, and are theoretically correct, in 

 practice for organization purposes the special site, stand and 

 market conditions must modify the judgment based on them. 

 The figures also support the contentions of soil rent theory, that a 

 low interest rate is in part compensated by a value increment, as 

 well as by price increment. To exhibit the latter, an interesting 

 table is given showing the change in price for the celebrated 

 400-year-old Rothenbuch oaks, which from 1860 to 1910 for the 

 largest sized logs rose six-fold, 4 per cent per annum (from 25 

 cents to $1.54 per cubic foot), although the lower sizes increased 

 less in price, II and III class at 3 per cent; the lowest from 13 

 cents to 20 cents. 



From the discussion on the value increment of beech, which is 



