ESTIMATING A PART OF THE TIMBER 



257 



207. Actual Estimate or Measurement of the Dimensions of Every 

 Tree of Merchantable Size. This is known as a 100 per cent estimate 

 and differs radically from the total ocular estimate of stand just 

 described. It consists of recording the dimensions of each log on the 

 tract in case no volume table is used, or with a volume table, the dimen- 

 sions of every tree of merchantable size. The total volume is then 

 simply a matter of computation. 



The trees are tallied by dots and lines, in blocks of ten, as indicated 

 in the following table, which shows the marks corresponding to dif- 

 ferent numbers: 



1 2. s-4, 5, 6 7 8 9 10 



• " •: :: r. n n n n 



When diameter alone is being tallied, a single column giving diameter 

 classes suffices for each species. Where the height, either total or 

 merchantable is also recorded for each tree tallied, each species will 

 require a tally similar to 

 that shown below. 



Where several species 

 are tallied by both diameter 

 and height, it is not cus- 

 tomary to make half-log 

 divisions, since too many 

 columns would be involved. 

 Where the top diameter of 

 logs, instead of D.B.H. , is Fig. 55. — Method of tallying trees by diameters 

 the point tallied, the same and lo e lengths, 



system of diameter classes 



or tallies is used. It is possible to combine this tally of D.B.H. for 

 one species with top diameter of logs inside the bark for others, using 

 the same horizontal columns for diameter in each case. 



208. Estimating a Part of the Timber as an Average of the Whole. 

 Where the greatest possible accuracy is demanded, it is obvious that 

 100 per cent of the trees should be measured. Only in extreme cases 

 can this be done, owing to the excessive cost. The process of measure- 

 ment accomplishes no constructive change in the form of the forest 

 (§6) as does logging or silviculture, but is of use merely in the orderly 

 management of the business of regulating these operations as to location, 

 quantity and time. Efficiency then demands the reduction of the cost 

 of obtaining these statistics to the lowest figure which will suffice for 

 the proper conduct of the business and avoid loss through errors in 

 appraisals of quantities and values. 



With timber whose average value per tree is small, the cost of meas- 



