Forest Mensuration 35 



PARAGRAPH LVI. 

 SCHENCK'S GRAPHIC METHOD. 



This method, as well, can be used only for sound woods. No calcu- 

 lation is required. The procedure is : 



1. Caliper the whole wood. 



2. Cut sample or type trees of small, big and average .diameters, find 

 the contents of each tree separately, together with the composition of 

 contents as logs, fuel and bark. 



3. On a piece of cross section paper, use as many units along a hori- 

 zontal line as there are trees (or tens or hundreds of trees) calipered. 



4. Mark the unit which each sample tree, according to its diameter, 

 would occupy if the biggest tree were placed to the right and the smallest 

 to the left of the horizontal line. 



5. Enter over the marked units the volume of the type trees (accord- 

 ing to the composing factors, if required) in square units. A square unit 

 might correspond with ten feet board measure, or with i/ioo of a cord, 

 etc. 



6. Draw a line joining the ends of the columns, adjusting it by an 

 average curve. 



7. Measure the space (in square units) between the curve and the 

 horizontal line with the help of a planimeter; the number of square units 

 giving directly the number of feet Doyle, or of cords, etc. 



If there are several assortments of volumes, several curves must be 



drawn. This method allows of separating the volumes of trees allotted 



to the several diameter classes. Mathematical errors are, practically, 

 excluded. 



PARAGRAPH LVII. 



FACTORS GOVERNING THE SELECTION OF A METHOD OF VALUATION SURVEY. 



In the case of a valuation survey ("stock taking") in the wopds, the 

 following points must be considered : 



o. The degree of exactness required, which depends on the purpose 

 at stake (e. g., scientific investigations, or preparation for logging, or 

 taxation). 



b. The regularity, uniformity and soundness of the growing stock. 



c. The minimum diameter of logs ; assortments ; marketability of spe- 

 cies. 



d. The possibility of cutting sample trees. 



e. The expense permissible. 



The question usually arises whether the entire forest or sample plots 

 only must be surveyed. The answer depends on the configuration of the 

 ground, uniformity of the growing stock as to size, age, species and 

 quality of its components ; further on the value of stumpage, on the accu- 

 racy required, on the available time and on the available funds. 



