VOLUME OF THE TREE. SYSTEMS USED 159 



System A. Disregard stump height. Take diameter at every 

 10 feet from ground to tip. Record length of tip above last 10-foot 

 taper. 



This method permits of accurate averaging of these diameters on 

 different trees to obtain average form, and also gives the total cubic 

 volume of the tree. But it is unsafe to rely solely upon these measure- 

 ments for the volume of the first 10-foot log, which should be supple- 

 mented by stump taper measurements, taken at 1, 2, 3, 4 and 4 J feet 

 from the ground. This gives a complete record of form and an accu- 

 rate basis for total volume. 



By means of form or taper tables (§ 167) based on these measure- 

 ments, the diameters at any other points may be obtained from dia- 

 grams, and the volume of the tree can then be calculated for any unit 

 of product. 



System B. This method is a compromise between measurements 

 intended solely to secure form or total cubic volume, and those required 

 for merchantable volume (§ 145). The height of stump is first recorded 

 and the height of upper diameters is then taken from the stump as a 

 base. As stump height tends to increase with diameter of tree, the 

 upper measurements of larger trees fall at higher points on the bole, 

 by just the difference in stump heights. This inaccuracy is usually 

 accepted and the diameters which fall at equal height above the stump 

 are averaged together. 



The length of log or interval adopted for upper diameter or taper 

 measurements by this method is a multiple of 4 feet. Four-foot inter- 

 vals give closest results, and correspond to cordwood lengths. A more 

 common interval is 8 feet, corresponding with the standard length of 

 cross-ties.. Greater lengths give less accurate permanent data. If 

 only the 16-foot tapers are required for the immediate purpose of the 

 table, it is comparatively little extra work to take the 8-foot points 

 as well, for future use if needed. 



System C. By this method the logs as cut by the sawyers are 

 measured as they lie, for diameter and length. As these commercial 

 lengths vary, the taper measurements for different trees will fall at 

 several different points even for the first log, and require tabulation 

 at 2-foot intervals. Except when measured for total cubic feet, the 

 resultant volumes will vary according to the lengths cut (§ 43), and 

 not solely according to the dimensions of the tree as by Systems A 

 and B. No advantage is gained by the securing of volume correspond- 

 ing to the used lengths of the tree measured, since in every logging 

 job, the average of lengths used will differ. This method is therefore 

 inadvisable. But a record can be made on the analysis blank of the 

 log lengths actually cut, and their scaled contents, to determine the 



