TABLES RELATING TO PARTS III AND IV 277 
scaling 18 feet by the Scribner rule, may be deducted 
from the tabular values. It is not a large percentage of 
sizable timber. If logs are cut and scaled in longer lengths 
than 16 feet, adjustment may be made on somewhat the 
same plan, as explained on pages 172 and 173. This 
last adjustment may be made in any kind of table. 
In most of the western tables total height is neglected 
and the trees are classified by number of merchantable 
log lengths. That follows the usual practice in western 
cruising, practice connected apparently with the great 
height of the timber. There are, however, two types of 
tables in this class — those in which the timber is scaled 
up to a single fixed diameter and those in which the top 
diameter varies with actual utilization. Nos. 28 and 22, 
tables for Washington hemlock and for yellow pine of 
the Southwest, illustrate these two types. 
The chances of error in connection with tables of the 
type of No. 22 (leaving out of account now individual 
variation of form) may be illustrated as follows: A 
tree 31 inches in breast diameter with five 16-foot logs is 
given a volume of 1410 feet and the figure is based (see 
table 21) on utilization to a 13-inch top limit. If very 
close utilization should secure another log length above 
that, the fact would not greatly concern an estimator 
because it would be so small in volume proportionally. 
Even if one less log were taken out than the table con¬ 
templates, it would amount to but 97 feet, 7 per cent of 
the tabular volume. What is of more importance, how¬ 
ever, is that the height at which the tree reaches 13 
inches diameter be estimated correctly. Should this 
height be set a log length too low and the tree scored down 
as of four logs instead of five, the value derived from the 
table would be 1230 feet instead of 1410, 13 per cent too 
little. An error of equal amount results if the tree is 
scored a log too long. 
Tables of the type of No. 28, scaling the logs up to a 
small diameter uniform in all sizes of timber, present an 
appearance of greater accuracy, but as a matter of fact 
much larger errors than the above may arise from care- 
