TRUE CONTENTS 277 



Then, again, practically the same result is obtained by 

 the following : 



(Mean quarter girth in inches) 2 x length in feet 



"3~ 



This is known as the quarter girth measure with 113 divisor, 

 and is often adopted (under bark) by the railway companies. 

 In order to find the mean sectional area of standing 



timber by the formula - , the sectional area is taken at 



4 



breast high, and then the mean sectional area is found by 

 multiplying by the form factor, 1 and hence the true contents 

 may be found. 



Calliper Measurement. This is a method used in the 

 royal dockyards and elsewhere for " round " timber. It 

 shows rather the stowage requirements, than the contents. 

 For the contents, as computed by this method, give a result 

 far greater than the true mathematical contents ; as it sup- 

 poses, as it were, that the round timber is square, and that the 

 side of the square is equal to the diameter of the round timber. 



To find the contents, the mean diameter is taken with 

 the callipers and the contents are equal to : 



(Mean diameter in inches) 2 x length in feet 

 144 ~ 



The following figure illustrates the method : 



Thus the shaded portion is included in the measurements 

 though it does not exist. 



1 Vide Chapter XVI I. 



