FORM FACTORS 



433 



as nearly representative of the whole area as possible ; and 

 they should never be taken (or only a very small proportion 

 of them) on the edges of rides or roads, as, in such places, the 

 growth and development is usually greater than elsewhere. 



The principle involved in these two methods of measure- 

 ing large areas of timber should certainly be adopted largely 

 in this country. If the true contents over bark be com- 

 puted, the contents by quarter girth measurement under bark 

 (allowing I inch to I foot) will be approximately 65 per 

 cent. 1 



The quarter girth measurement contents can also be found 

 by using a reduced form factor when finding the contents by 

 the true basal area method, i.e., by taking the diameter. 



Thus, in the case of a crop of Beech, the reduced form 

 factors would be as follows, if the average form factors in 

 continental tables, according to the height of trees, were : 



However, in most cases it will be preferable to take the 

 quarter girth measurements at breast high, and then to use the 

 unreduced form factors direct, if form factors are going to be 

 used at all. But the application of continental form factors 

 must at present be used with great caution in this country ; 

 for, speaking generally, crops of timber are not raised in this 

 country in the same density as was the case with the crops 

 from which the average form factors have been taken. There- 

 fore, it will be wise to omit the use of form factors, at any 



1 Vide Chapter XIII. 



2 E 



