PRACTICE OF TIMBER ESTIMATING 197 



constructed on principles that have very seldom been 

 employed elsewhere. After basal diameter, taper per 

 32-foot 1 log is the next factor allowed for, total height of 

 the tree is disregarded, and number of logs is the third 

 factor in the tabulation. This has reason behind it as 

 well as experience. In timber of such dimensions total 

 height is not readily estimated; the lower logs of the tree 

 are very much the largest and far the best in quality; 

 a log more or less in the top, comparatively small in size, 

 full of large knots and liable to be broken up in felling, is 

 of small account in the estimate anyway. 



In connection with these tables, basal diameter also is 

 handled in a peculiar manner. In some tree species thick- 

 ness of bark is very variable, while the root swelling of 

 large trees frequently reaches to the height of a man and 

 higher. Diameter therefore is taken as nearly as may be 

 where the tree takes on its regular form, considerably 

 above breast height as a rule; deduction is made for any 

 swelling not thus allowed for, and double the thickness 

 of bark as actually found is then subtracted. By this 

 means, the wood alone is dealt with, and basal diameter 

 is aligned with the general shape of the tree. 



In view of the facts above mentioned it is clear further 

 how windfalls furnish the best obtainable assistance to 

 the cruiser's judgment in respect to height and taper, 

 also that the diameter tape and Biltmore stick possess 

 advantages over the caliper. Then two additional prob- 

 lems arising out of the size of the trees confront the cruiser : 

 first, breakage in felling is a much more important factor 

 than elsewhere, and its amount varies widely with the 

 ground conditions; second, the defect arising from decay 

 and other sources, very hard to judge, to detect even, in 

 timber of this height, has to be handled with extreme 

 care careful looking, the examination of windfalls, 

 experience, perhaps the outturn of adjacent timber serv- 

 ing as a guide to it. 



The "forty" is the ordinary unit of area for cruising 

 and a timber report, and it is gridironed with straight 

 line travel. Pacing serves ordinary purposes as a dis- 



1 Tables based on 16-foot logs are also in existence. 



