36 



12. Taluation survey hy means of tables of yield. 



In this method the surveyor must determine three essential 

 points : — 



(«) The quality of the soil and locality. 



(b) The density o£ the crop. 



(c) The age of the crop. 



The older tables of yield drawn up in Germany omitted the first 

 point. In the tables recently issued, for each forest or class of 

 forest a certain convenient number of classes of soil and locality are 

 established according to the height attained by the trees in each. 

 Hence, for any particular crop in question, we have only to ascer- 

 tain the average height of the trees, in order to know at once the 

 quality of the soil and locality. 



The age of the crop will be known from its past history, if it 

 has one going back far enough ; or it must be ascertained by ring- 

 countings, if some constant relation exists between the number of 

 concentric rings and the number of years in which this number of 

 rings is produced. Otherwise there is no means of obtaining it 

 with any degree of accuracy. 



The density of a crop is an extremely diflBcult thing to estimate 

 with sufficient accuracy. It can,, of course, be determined by mea- 

 suring the girths of all the trees and thus obtaining their 

 . aggregate basal area, but this means almost as much work as far 

 more trustworthy methods of valuation survey with the aid of 

 sample trees. 



13, Choice of the method of valuation survey. 



Prom -what has already been said in describing the various 

 methods of valuation survey, it is clear that this choice in any 

 given case depends— 



(a) on the required degree of accuracy, 

 (6) on the nature of the crop, and 



(c) on tlie number of individuals that may be felled as sample 



trees. 



If the money-value of a crop is soiight, as would be required if 



the crop is to be sold or the forest expropriated, or if the owner 



wished to obtain accurate statistical data regarding his property, 



XJrioh's method should be emploj ed. For the purposes of a work- 



