PRACTICE OF TIMBER ESTIMATING 203 



No. 2 (or Merchantable] logs shall ho not less than 16 

 feet long and which, having defects which prevent their 

 grading No. 1, in the judgment of the sealer, will he 

 suitable for the manufacture of lumber principally in 

 the grades of Merchantable and better. (Merchantable 

 lumber must be free from knots or other defects in size 

 or numbers such as to weaken the piece.) 



No. 3 (also called No. 2) logs shall be not less than 16 

 feet long which, having defects that prevent their being 

 graded higher, are, in the judgment of the sealer, suitable 

 for the manufacture of Common lumber. 



Cull logs shall be any logs which in the judgment of 

 the sealer will not cut 33^ per cent of sound timber. 



An essential to reliable timber grading is experience, a 

 background of knowledge of the out-turn of similar tim- 

 ber. In the next place, close examination of the stand 

 is required as to the number and size of limbs and knots 

 and for indications of these, or of other defects, that 

 may lie beneath the surface. Age is a help here (these 

 stands are commonly even-aged over considerable areas). 

 Many cruisers go no farther than this and set percentage 

 figures for log grades as the result of a broad judgment. 



When further detail is thought desirable, the volume 

 tables before mentioned are of assistance, giving as some 

 of them do for a tree of given diameter, taper, and mer- 

 chantable length the percentage each successive 32-foot 

 log bears to total contents. One standard volume table 

 contains the following directions : 



"Determine the percentages of the different grades as 

 contained in a given percentage of the trees on each 40 

 acres by selecting, for instance, an average tree on each 

 tally and carefully determining the percentage of the 

 different grades of logs contained in these sample trees 

 and applying the average to all trees on the forty." 



To illustrate, in the notes on page 199, 11 trees, 46 M 

 feet, are scored down in the column of living fir, giving an 

 average volume of 4200. 4 inches taper and 4 logs may fit 

 this timber; if so, a tree yielding 4330 feet (see extract from 

 taper table) gives a close approximation. Of such a tree 

 a 32' butt log constitutes 37 per cent, the second log 28 



