172 FARM FORESTRY 



Expressed as a formula : 



in which V is the volume of the log in cubic feet. B r is the 

 area of the middle cross-section of the log in square feet. 

 L is the length of the log in feet. 



A more accurate method, but requiring one more measure- 

 ment, is to average the basal areas of the small and large ends 

 of the log and then multiply by the length of the log. The 

 average diameters at the top and bottom of the log are meas- 

 ured accurately and the corresponding basal areas in square 

 feet are found from the basal area tables. These are added 

 together and divided by two to get the average basal area. 

 The result is multiplied by the length of the log in feet tn 

 get the cubic contents of the log. 



Expressed as a formula: 



in which V is the volume of the log in cubic feet. B arid b 

 are the areas in square feet corresponding to the diameters 

 of the two ends of the log. L is the length of the log in 

 feet. 



Board Measure. The number of board feet that can be 

 sawed from logs of different diameters and lengths is shown 

 in tables called log scales or log rules. A log table or rule 

 is a tabulated statement of the contents in board feet of logs 

 of different diameters and lengths. Knowing the diameter of 

 the small end of a log inside the bark and the length of the 

 log, the number of board feet contained in the log can be 

 found from a log rule. There are over forty such rules in 

 common use, often differing widely in the number of board 

 feet given for logs of the same size. The amount of lumber 

 that can be sawed from a log of a certain size is not definite. 



