342 Forestry Quarterly 



base of which is — but whose height must be more than , 



3 3 



perhaps A^/id. This forces one to investigate whether really the 



height in this case is greater than lOO^i (the normal condition of the 



h 

 formula), or whether / is unusually large. The relation —=100 



d 

 is easily impressed upon the eye and helps greatly in discovering 

 divergence. 



By securing in this way a conception of the forms, ocular 

 estimating is aided and developed. 



Similarly, a special conception of the increment can be developed. 

 This is done by using Breyman's increment per cent formula. 



The difficulty of estimating form factors, the author suggests, 

 might be overcome by photographic representation of sample trees 

 with various form factors, on which the eye could practise. Such 

 photographic "estimating pictures" cotdd also be used to practise 

 the eye in other directions. 



In conclusion, the author once more accentuates the necessity 

 of developing the ability to estimate correctly, which he calls the 

 "art" in mensuration. Especially in forest organization it is 

 needed, for the tables are after all only average or limit values and 

 in a given case can be said "to be always wrong." They require 

 adaptation to the peculiarity of the stand in hand, which no table, 

 no measurement, no rule can fully represent. This individualizing 

 between limits set by theory and investigations laid down in yield 

 tables is the function of the estimator, who, to be sure, must be 

 an expert. 



Zur Schdlzung des Festgehalts von Bdutnen und Rundholzern. Allgemeine 

 Forst-und Jagd-Zeitung, October-November, 1915, pp. 225-234. 



Oberforstrat Frey inveighs against the 

 Forest soil rent theorists and their expectancy 



Valuottion values, which, according to him, have no 



and practical and only doubtfully theoretical 



Organisation significance, for they assume that wood 

 prices and interest rates remain the same 

 forever, which is contrary to experience. The arbitrary choice of 

 interest rate leads to calculations which are difficult to gibe with 

 the results of an organized forest management in an actual, exist- 

 ing forest. He sneers at the advice of these calculators not to 



