Forest Mensuration 201 



the estimator will find that he rarely has to change his 

 guess when the calipers have been applied. Till the 

 estimator has become very expert, it is best to use the 

 caliper check each day when beginning work, for the eye 

 is apt to lose its cunning over night and needs tuning up. 



The eye can best be trained to measure heights by the 

 use of a ten- or better, a sixteen-foot pole, — the length of 

 an ordinary log. Stand the pole against the base of a 

 tree. Retreat a few paces and note how high it comes on 

 the tree and how many times it could be contained in the 

 height of the tree, or to the top of the top log. Together 

 with this practice, estimate the diameters at the various 

 log lengths. In this way a very fair idea of the number 

 of logs a tree contains can be reached. When cutting 

 timber, this process should be checked by first estimating 

 the timber carefully and then measuring the log lengths 

 and diameters on the felled tree. 



The next thing that must be learned is the thickness 

 of the bark of the different species at different heights. 

 It varies considerably in thickness from the ground to the 

 top of the first log, but above that it is fairly uniform. 

 This can best be learned from the observation and measure- 

 ment of felled trees. The testing of the bark of standing 

 trees at breast height is not a good ,test. In estimating 

 the diameter of logs inside the bark, do not forget to double 

 the thickness of the bark before subtracting it. 



When the eye has been trained in this way, the actual 

 work of estimating may be started. The method used will 

 vary somewhat with the size of the tract and the purpose 

 of the owner. The smaller the tract the more accurately 

 the work can be done. 



