FOREST ECONOMY. 207 



at which the different stands are growing. Besides 

 this stock taking ^ and measurement of accretion, 

 accompanied by a description of the forest condi- 

 tions of the different parcels or stands, all of which 

 exhibit the present status of the forest, the con- 

 struction of so-called " normal yield tables " is 

 needed. These are the result of measurements 

 on the most perfect, normally stocked stands of 

 various species, stating what the contents of such 

 stands should be at different periods of life, gener- 

 ally from ten to ten years, giving, therefore, by 

 decades the progress of accretion under normal 

 conditions for the area unit. With the aid of 

 these tables (see Appendix to Chap. VI) the sum- 

 mation of which permits a statement of the normal 

 stock required for different rotations, the sustained 

 yield can be ascertained by comparing with the 

 actual conditions, and gauging the felling budget 

 as intimated in the formula given above. 



In order to translate th? statements of volumes 

 recorded in the yield tables into values, which is 

 needed to permit finance calculations, the progress 

 of accretion, or of accumulation of stock in size or 

 assortments of different value, must be ascertained. 

 This leads to the construction of financial yield 

 tables, which give the value from period to period 

 either of the unit measure of wood (cubic feet, feet 

 B.M.) or of the unit measure of area (acre) nor- 



1 For this quantitative survey, the term " valuation survey " has 

 been adopted by English writers with doubtful etymologic propriety. 



