52 BULLETIN 718, U. S. DEPARTMENT OF AGRICULTURE. 
rule of more ancient origin, which gives the same results, is to deduct 
4 inches from the diameter of the log as an allowance for sawdust 
and slabs, then multiply the remainder by half itself, and the product 
by the length of the log in feet, and divide by 8. The quotient will 
be the number of square feet contained in the log. Still another giv- 
ing the same contents is. deduct 4= inches and square the remainder, 
adding to or deducting for the aliquot parts of a longer or shorter 
log. 
The Doyle rule gives less values in board feet for 16-foot logs up 
to 28 inches in diameter than the Scribner or the Decimal C rule, 
and above that diameter gives greater values. Between 22 and 28 
inches in diameter, however, there is only a slight difference between 
the two rules. The 1l single logs ranging from 8 to 21 inches in 
diameter scale by the latter rulel2 per cent more than with the Doyle, 
though logs scaled by the Decimal C rule overrun the log scale by 
an average of 10 per cent when manufactured into lumber. 
The requirements of the Forest Service call for the measurement of 
sound material in the log irrespective of grade. Allowance is made 
for bad defects, such as rot, shake, check, cat face, crooks, worm- 
holes, etc., or a serious combination of one or more such defects in 
one log. In timber of high commercial value, logs are classed as 
cull that have two-thirds of the gross scale defective; in the case of 
inferior species, such as fir, lcdgepole, and balsam, one-half of the 
gross scale. 
It very often happens that timber or logs containing only one-third 
of the gross scale in merchantable lumber will not pay the cost of 
handling unless the lumber obtained is high grade. In such cases 
the scaler should possess a knowledge of grades and be qualified to 
differentiate between a leg that pays for merchandizing and one 
that does not. 
The only true analysis of what a defective log will scale is found 
by seeing it opened up in the mill. A scaler's ability to make proper 
allowance for defect hinges on his experience in this particular re- 
spect. Defects such as large loose or unsound knots, an occasional 
knot hole, a great deal of pitch and pockets, some red rot and bad 
season checks, large wormholes, and any amount of blue stain, unless 
combined in one log. affect merely the quality or grade and not 
the quantity of merchantable lumber produced from the log. They 
are therefore not recognized as justifying a scaler in discounting 
the gross scale of a log. 
The fact of logs overrunning the log scale — that is. cutting more 
board feet than is shown on the Decimal C rule — should not be 
considered by a scaler in making allowance for defect. This matter 
of overrun is, in Forest Service sales, taken into account when ap- 
