96 



THE MANAGEMENT OF WOODLANDS. 



3. Whole crops of Timber are best measured by selecting one 

 or more sample plots representing a fair average of the whole 

 crop, and carefully ascertaining their cubic contents, and then 

 multiplying the result by the proportion which the whole crop 

 bears to the sample plot or to the mean of the several sample 

 plots measured. 



The diameter (or girth) of all the trees in each sample plot 

 having been measured and registered in a field-book showing 

 the different kinds of trees and different diameters, varying by 

 1 in. (or girths varying by 3 in.), the diameter or girth of the 

 true average sample stem can be found by the simple rule that 

 if four-tenths of the total number of stems in a measurement of 

 the whole crop or of a sample plot of average quality be taken, 

 and a count back made to this extent from the largest stem down- 

 wards, the result will invariably indicate the diameter - class 

 containing the mean average stem for the crop or the sample plot. 



For example, say a 3-acre plot of 

 Larch contains 2, 704 trees as here re- 

 gistered, then the true mean average 

 stem will be found by taking four- 

 tenths of 2704, i.e., 1081, and count- 

 ing back for this number from the 

 largest diameter - class downwards, 

 which leads one to the 11 -in. class.* 

 By selecting and carefully measuring 

 the cubic contents of one or more 

 average specimens of this class, 

 taking their mean, and multiplying 

 the result by 2704, the cubic con- 

 tents of the whole 3-acre plot will 

 be found. 



Having ascertained the true average diameter- class, one then 

 seeks out stems of this true mean diameter, measures 2 or more 

 such mean stems accurately (felling them for this purpose, if 



