280 TIMBER MEASURING 



By Quarter Girth Measurement (under bark) : 



If an allowance for bark of I inch to I foot is made, the 

 contents over bark must be reduced by Jth. 



Hence, the contents under bark equals 65 T 5 ^th cubic feet, 

 i.e. y nearly 65^ cubic feet (under bark). 



This shows a deduction of 34! l per cent, as compared 

 with the true contents (over bark). 



By Die Square Measurement out of section at the 

 smallest end : 



Contents = l6 ** l6 ^* x 2 8J 



lol 



= 42^ cub. ft. 

 * As the taper is I in 7, the quarter girth under bark at small end equals i6J. 



This shows a deduction of 57 \ per cent, as compared with the 

 true contents (over bark). 



By Die Square Measurement out of the average 

 section : 



Contents = l8 *g l8 ** x 28* 



lol 



= 53^t cub. ft. 



* \\ inches deducted for bark, as in practice. 



t This is mathematically rather too much, as ij inches only had been deducted, 

 instead of if, which should be adopted in order to show the correct percentage. 



1 For quickly comparing the true contents over bark as found in 

 continental tables, the deduction may be taken as 35 per cent. ; and then 

 the true contents, if divided by 10 and multiplied by 6^, will give the 

 quarter girth contents under bark. This, however, will usually be too 

 great, as continental tables usually include all branchwood, or else down 

 to 3 inches diameter. If it be required to compare the former with 

 quarter girth contents down to 3 inches diameter, no definite rule can be 

 given ; so also no definite rule can be given if it be required to compare 

 the true contents of timber down to 3 inches diameter with the quarter 

 girth contents down to 6 inches diameter, for so much will depend upon 

 the size of the trees. 



In the latter case, if the trees be large, say 40 cubic feet quarter girth 

 each, another 10 per cent, deduction might suffice, making 45 per cent, 

 in all ; so that the true contents down to 3 inches diameter should be 

 divided by 10 and multiplied by 5^ to bring to the quarter girth contents, 

 down to 6 inches quarter girth, under bark. But if the trees are smaller 

 the total deduction would be 55 per cent, or more. 



