48 MEASUREA1E>-T OF WHOLE WOODS. 



the desired degree of accuracy, and the voUime of each section 



is ascertained separatel}' by the formula : — 



Volume = area of circle in the middle X by the length of 



the section : 



V = s,„ X h. 



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. Ex- 

 perience 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 Volvmes of the Classes and of the Whole Woo<l. 



Here several cases may occur : 



(1.) One sample tree has been measured in each class, 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 — 



T' = volume of whole wood, 



I'lj y^, ^3 . . . = volumes of classes 1, 2, 8 . . . 



