I)1:TKUM1.\AT10N of the MIDOI^Ji DIAMKTKK 805 



a distance of- — 1.5, or 3 meters, from the foot of the tree, and 



from this point measure n and n' as explained above. 



He finds, for example, in an actual case that /;' = 3 and ;; ^ 5. 

 Then the desired coefificient of form 



/=- X i-4 = fx 1.4= •6X 1. 4- or 



I! 5 



/=.84. 

 The product — X 1 -4 can be easily calculated in the head. It equals 



in effect the sum + — X .4, or in the example above .6 4- -6 X -4. 

 n 71 



or .6 -\- . 24 ^ .84. 



This method for determining the coefificient of form is generally ap- 

 plicable. Repeated tests have proved that it is accurate, and con- 

 sequently susceptible of rendering real service in estimating standing 

 trees. 



Comment by W. N. Sparhazck : 



For work requiring a considerable degree of accuracy the method 

 described must be used with a great deal of care. Due allowance must 

 be made for height of the eye, care must be taken that the observer 

 stands on the same level as the tree (or, on slight slopes, addition or 

 deduction may be made for the difference in level when allowing for 

 the height of the eye), and the readings of apparent diameters must be 

 made on the right points on the bole. 



Failure in these respects will lead to rather serious errors in the 

 results. For instance, take a tree 20 inches d. b. h. with a 50-foot 

 merchantable bole and a diameter at the middle of 16 inches. Accurate 

 use of the above method will give /== .8, whence d' (computed from 

 d = 20) will be 16 inches. If, however, readings are made from a point 

 25 feet from the tree (no allowance for height of eye), / will be .88 

 and d' = 17.6 inches, or i .6 inches too high. 



If the tree stands on a 15° slope and the readings are rnade at the 

 correct horizontal distance from it, but directly downhill from it, / will 

 be .y2 and ^'=14.4 inches. If the distance is measured along the 

 slope and not corrected to horizontal, d'^14.2 inches. If readings 

 are made on the same slope above the tree, results will be 18.9 and 18.6 

 inches respectively. 



