THE LOG AS THE UNIT IN ESTIMATING 141 



is used, the method requires a count and tally by different sizes, and 

 gives rise to many systems of estimating, depending on whether the 

 entire area or only a portion of it is to be counted. 



119. The Log as the Unit in Estimating. When the product to 

 be estimated in board feet is lumber, the log becomes a convenient 

 and much used unit for estimating. Lumber is measured or scaled 

 in the log by a given log rule. The contents is given for logs according 

 to their diameter inside bark at small end, and length. Hence a tally 

 of the top diameter inside bark and the length of. each log in a tree, 

 and the use of a log rule, will give the board-foot contents of the tree. 

 If every log is so tallied the stand is measured by merely totaling the 

 contents of the logs, without computing the volume of separate trees. 



No further volume basis is needed in this method than the log 

 rule or scale stick. But the cruiser must know the amount of taper 

 in each log, the thickness of bark to be deducted, and the log length 

 to use in estimating. 



Log lengths as actually cut are determined by the crooks and other 

 peculiarities of each tree. But in estimating timber, these variable 

 log lengths are disregarded and a uniform or standard length is adopted 

 which conforms within reasonable limits to the average log length most 

 frequently used. For eastern conifers this is 16 feet, while hardwoods 

 may require 12 feet. On the Pacific Coast, 32 feet is used by many 

 cruisers. If logs when cut average shorter than the standard, the 

 scaled contents of the logs will over-run the estimate, while if longer 

 logs are cut, the scale will fall short (§ 83). 



The method of tallying the logs in a tree is as follows : 



1. Estimate or measure the diameter of the butt log either at the 

 stump, at 4J feet from the ground, or at 1 foot above the butt swell, 

 choosing one of these methods to the exclusion of the others. Foresters 

 use 4| feet as the accepted standard. 



2. Deduct the double thickness of bark to obtain the diameter, 

 inside bark, at this point. 



3. Estimate the number of inches to deduct from this diameter for 

 taper, to obtain the diameter at the top of the first log of standard 

 length. This and all upper estimates of diameter are inside the bark. 



4. Estimate by eye the number of standard logs in the tree, to the 

 limit of merchantable size. The top diameter at this point should 

 be known or estimated, inside bark. 



5. From the 'diameter of the top of the first log, inside bark, deduct 

 successively the estimated taper, in inches, to obtain the diameter 

 of each remaining log. 



An alternate plan frequently used is to measure the diameter out- 

 side bark at the butt, or at 4J feet, subtract the taper outside bark 



