THE PROBLEM OF MAKING VOLUME TABLES 575 



board foot tables which may be used in the measurement of a large 

 number of trees, as in timber survey work. 



In timber estimating as practiced on the National Forests the volume 

 table is one of the forester's most necessary tools. He needs a good 

 diameter tape, or calipers, or Biltmore stick, a good hysometer, and a 

 good volume table. So far I feel that, rather inevitably, our American 

 volume tables are of the rough stone era in forestry. It is now time, it 

 seems to me, for the scientific branch of the Service to equip the admin- 

 istrative officers with better volume tables, good tools with which to do 

 their timber estimating. I feel that this is work for the Branch of 

 Research rather than for the Administrative Branch of the Service, 

 because, as I have already said, volume-table preparation is not straight, 

 simple mathematics. It involves principles which have not yet been 

 worked out. There is field for the investigators in searching for the 

 best principles of volume-table preparation, in standardizing volume- 

 table practice, in inventing the much-wished-for universal volume table. 



The next question is, What is the matter with our present volume 

 tables? Then, What must be done to secure an ideal set of tables? 



An examination of our tables show that they are as variable in 

 construction as they are numerous. Some are based on merchantable 

 height ; some on total height. Some assume utilization to a fixed top 

 diameter; others conform to actual utilization practice, with every gra- 

 dation between. Some are discounted for defect and breakage; others 

 are based on sound, normal trees only. Some assume a standard 

 stump height ; others are indefinite on this point. Some are based on 

 measurement at regular 16-foot intervals; others are from measure- 

 ments taken almost at random up the bole of the tree. Some are based 

 on young and old trees jumbled together, and are, therefore, really 

 applicable to neither young or old timber, or, similarly, are made from 

 measurement of trees from several types, and therefore perhaps not 

 accurate in any one type. Most of them are based on the Scribner 

 rule, the adopted scale rule of the Forest Service ; in this particular 

 there is general conformity. 



Tables as variable as this are really safe only in the hands of the 

 maker, for unless the construction of a table is understood by the user 

 he wall apply it unintelligently and probably erroneously. Unfortu- 

 nately, we have very little information to show how accurate our 

 tables are. Where discrepancies in our estimates have been found, the 

 errors have been ascribed more often to errors in the allowance for 



