48 VOLUME OF WHOLE WOODS. 



The volume of all irregular pieces, including root and 

 branch wood, is ascertained : 



either by the xylometric method, 



or by proportionate figures, 



or by measuring their volume stacked, and multiplying 



it by known reducing factors, if such are available. 

 The xylometric method has been explained in Chapter I. 

 Proportionate figures are obtained from actual fellings. If 

 it has been found that in the felling of a wood, every 100 cubic 

 feet of timber are accompanied by, say, 20 cubic feet of fire- 

 wood, that proportion can be applied to other woods of a 

 similar description. 



The determination of the volume of sample trees by means 

 of form factors or volume tables can be highly recommended 

 whenever suitable data are available, because they give averages, 

 and that is just what is wanted in this case. Experience has 

 shown that form factors and volume tables are applicable 

 for a considerable distance outside the locality for which they 

 have been prepared. 



/. Calculation of the Volumes of the Classes and of the whole Wood. 



Here several cases may occur : 



(1) One sample tree has been measured, the dimensions of 

 which are exactly the average of the class. In that case the 

 volume of the class is obtained by multiplying the volume of 

 the sample tree by the number of trees in the class. 



If 



V= volume of whole wood, 



FI V Zf Vz . . . = volumes of classes 1, 2, 3 ... 



v lt v z , Vz . . . = volumes of mean sample trees of successive 



classes, 

 n lt n 2 , n s . . . = numbers of trees in successive classes, 



then 



V 1 = v 1 xn lf F 2 

 and 



F=F 1 +F 2 +F 3 +. . . = v l x 



