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- 



