55 



Botb formulae contain an error, the extent of which is 

 proportionate to the amount of difference between- the area 

 at the top and base, respectively, of the log, that is to say, 

 to its degree of taper ; and this error increases as the square 

 of that difference. The second formula always gives too 

 small a result, the first too great, the error of defect in the 

 one case being one-half the error of excess in the other. The 

 second formula has also another advantage for which it is 

 to be preferred. The ordinary modes of measurement and 

 calculation give, as a rule, too high a figure for the sectional 

 area concerned in each case. This excess is partly compen- 

 sated by the employment of the second;formula ; whereas the 

 use of the first would only exaggerate it. In order still 

 further to diminish error long logs should be measured in 

 two or more sections, the number of the sections increasing, 

 i.e., their length diminishing, with the taper of each log. 

 The contents of logs of regular shape and not exceeding 20 

 feet in length may, however, be deduced from their sectional 

 area in the middle. Longer logs, even if of regular shape, 

 should be cubed in two or three sections. All large round 

 logs should be measured singly. If the logs are stacked 

 so that they cannot be conveniently measured in the middle, 

 the mean of the sectional areas at the base and at the top 

 must be taken. The mean sectional area should not, 

 under any circumstances, be deduced from the mean of the 

 diameters at the two extremities respectively, or an error 

 of from 10 to 15 per cent, may result. Poles are seldom 

 cubed singly ; but nearly always in stacks, built up of poles 

 of one and the same length and of approximately the 

 same diameter. Their solid contents are generally ascer- 

 tained" by inspection from special tables. Straight and 

 regularly-shaped branches are measured in the same way as 

 logs. 



It must be observed, however, that while diameter 

 measurements give more nearly the actual contents of logs 

 and trees yet in practice the contents of round timber are 

 always calculated, for trade purposes in India and in England, 

 on the assumption that the sectional area is arrived at by 

 squaring the quarter girth. 



Square-cut timber must, of course, be cubed by the 

 formula : volume=lengthx width X thickness. 



The solid contents of small pieces, toppings and loppings 

 and irregular-shaped pieces from stumps and roots, are 

 obtainable by the water-method (their volume bemg equal to 



