Periodical Literature. 543 



He criticizes the inadequacy of methods to be used for determin- 

 ing stock and increment and of site classification and the rotation, 

 and looks with apprehension on the whole performance. 



"In this instruction are domiciled, as in olden times in the head 

 of the great philosopher, two opposing concepts, the 'pure' and 

 the 'practical'. Each tried to prevent the other from entering 

 and after all both came in ; but the 'pratical' must be satisfied 

 with a little corner in the transition regulations." 



Anweisung fiir die Forsteinrichtung in den Kgl bayerischen Staats- 

 waldungen. Schweizerische Zeitschrift fiir Forstwesen. February, 1912. 

 Pp. 56-63. 



Dr. Martin in his usual, clear and direct 



Statical style sets forth the value and proper appli- 



Formulae. cation of the formula he has developed in 



his classical volume on Forestal Statics, in 



defense against a reviewer who charges that thereby the author 



abandons the soilrent theory. The author refutes this charge but 



claims that for purposes of forest organization his formula is 



superior to the soil expectancy formula. 



The formula translated into our notation reads 



Y+T-(c+a)rr:S+St 



and places into relation the annual net income to the soil and stock 

 capital as a means of determining felling age and of other pro- 

 blems of forest organization. The general discussion on the use 

 of formulae is especially good reading for those who place too 

 much or too little value on them. The author points out that 

 "the securing of the highest possible net yield is undoubtedly the 

 most important economic principle of soil culture". All other 

 factors of economic production change in the course of time : 

 labor increases, capital grows, the forces of nature come more 

 and more under more thorough utilization, but the soil in its 

 quantity remains the same and largely also in its character; the 

 soil becomes rarer and hence more expensive, hence it must be 

 treated so as to secure the highest rent from it — the highest soil- 

 rent. While the theory of highest soilrent is a clear economic 

 principle of general application, the method of application may be 

 at fault. Surely, economic problems cannot be solved in a one- 

 sided mathematical manner. Many things which have an influence 

 on the soilrent are not capable of mathematical treatment, or only 



