10 THE THEORY AND PRACTICE OF WORKING PLANS 



then, since cXrXi=S, 



rXt 



Flury has calculated c for the chief species of Europe and for 

 various rotations as shown in the following table. These values 

 are for timberwood only. 



AVERAGE VALUE OF CONSTANT c 



Species 



Rotation in Years. 



80 



Spruce. Swiss foothills 



Swiss mountains 



Prussia ■ 



Fir. Wurttemberg 



Baden 



Scotch pine. North German Plains 

 Prussia 



Beech. Switzerland 



Prussia 



371 

 316 

 268 



205 

 226 



387 

 374 



276 

 219 



463 

 392 



354 



267 

 317 



454 

 456 



341 

 316 



405 

 379 



Applying Flury's constant c to McCarthy's white pine 

 yields as given above, the factor is as follows: for rotation of 

 30 years, ^ = .306; for 40 years, .365; for 50 years, .378; for 60 

 years, .421; for 70 years, .452; for 80 years, .475; for 90 years, 

 .493; for 100 years, .507; for no years, .518; for 120 years, 

 .525; for 130 years, .536; and for 140 years, .542. 



Thus the value for 140 years given above as 19,715,000 

 board feet would be corrected as follows: 



w2) = cXrXi = . 542X140X281. 64 



= .542X39,430X1000 (acres) = 21,371,000 board feet, 



which compares closely with the value 21,407,000 board feet 

 found by summation of the yield table. 



