YIELD TABLES 59 



in major classes, each major class containing, 

 as a rule, four inch classes. The major classes 

 were treated as separate groups, and the cubic 

 content of each was obtained by means of a 

 test tree. 



The actual basal area, or the total area of the 

 cross sections of all the trees breast-high, was 

 computed for each major class, and this num- 

 ber was divided by the number of trees in the 

 class. The product was the mean basal area 

 of the class, or the basal area of the average 

 tree. The diameter which corresponds to this 

 area is the diameter of the average stem of the 

 class. 



A tree was then chosen, as a sample or test 

 tree, which had the same diameter as this aver- 

 age tree. Care was taken that its height was 

 normal, and that it was not abnormally full- 

 boled or tapering. This tree was felled, and 

 analyzed according to the method already de- 

 scribed. The cubic content of each major class 

 was then calculated as follows : 



The cubic content of the whole class is to 

 the cubic content of the test tree as the basal 

 area of the whole class is to the basal area of 

 the test tree. Or if 



Y is the volume of the whole class, 



V the volume of the test tree, 



