THE PROBLEM OF MAKING VOLUME TABLES 577 



ployed, as in the case of the field assistants used on our timber surveys, 

 then a simple, conventional form of volume table is preferable. 



One type of table used by experienced cruisers on the Pacific Coast 

 is based on diameter inside bark above the root swell, on merchantable 

 height, and on the rate of taper per log. It is a theoretic table, in that 

 it is prepared in the office merely by assuming the required set of 

 diameters and height and a series of tapers and then applying the 

 corresponding scale for each log in the tree. Such a table is, of course, 

 absolutely correct if the tree or group of trees to which it is applied 

 corresponds to the assumed dimensions and taper. It presupposes, how- 

 ever, a uniform taper throughout the length of the merchantable stem, 

 and this is not true to life usually ; hence the table is theoretically 

 slightly off. A table like this has very great advantages. It is a uni- 

 versal table in a sense, in that one table will do for all species. Its 

 cost of construction is almost nothing, for it requires merely an adding 

 machine for a few days to make one that would do for all species for 

 all time. It has several disadvantages for Forest Service use. Since 

 it is based on three variables, it would complicate tallying on the survey 

 strips to such an extent as to make it impracticable so long as we 

 continue to tally each tree — a practice which I think we want to con- 

 tinue. It also requires the exercise of nice judgment in estimating 

 taper — a judgment which the high-paid professional private cruiser has, 

 but which the field assistants used on our timber surveys have not. In 

 short, a table of this kind cannot well be fitted in with our established 

 methods of timber surveys. 



Another type of table is Schenck's "Cruisers' Tables." These are 

 based on four variables — diameter inside bark at top of butt log, num- 

 ber of logs, taper, and mill factor of efficiency. These tables have an 

 advantage over the tables previously described in being practically 

 correct, universal in application; but they also have the disadvantage of 

 being impracticable to use where individual trees are tallied and of 

 being worthless in the hands of a field assistant who has not trained 

 judgment. It is my opinion, however, that our present system of cruis- 

 ing, which requires the tallying of every tree by size, demands the use 

 of a table built along the lines of our present conventional tables. 



If we decide to continue to use volume tables of the general style 

 now in use, it is very desirable that ther^ be systematization and 

 standardization throughout the districts. I do not mean that there must 

 be a rigid model to which all volume tables must conform and that 



