Difficulties and Errors in Stem Analysis. 17 



Example showing the error from " squeezing " calipers Y^" or 

 having the arms not parallel to the same amount. 



True D. bh. ^35.8 True vol. = 347.66 cu. ft. Errorof vol. ^12.50 cu. ft. 

 False D. bh. =35.3 False vol. = 33516 cu. ft. Per cent, of Error ^3.6. 



The error in amount grows with the size of the tree while the 

 percentage error decreases. 



Measurements in general are considered to be free of the ele- 

 ment of judgment, but it will appear from these considerations 

 that in forest work this is not so. There is a tendency on the 

 part of many, especially over zealous new men, to stretch for use- 

 less and uncalled for accuracy. Such men will be found running 

 the tape over the bumps and crooks of a hundred and fifty foot 

 pine and then reading the tape at the end of a very irregular 

 crown to the tenth of a foot. Such w^ork is not accurate but 

 merely a show on paper. Discretion as to the degree of accuracy 

 attempted is as needful as discretion in the manner of measuring. 



Other difficulties than those which have been mentioned occur; 

 for instance the counting of the rings. They are present, how- 

 ever, only with certain species, or conditions and are to be over- 

 come by special individual methods. 



A. S. Williams. 



