YIELD TABLES 73 



was laid off, and on the vertical lines or ordi- 

 nates the number of cubic feet. Normal curves 

 were then struck through the highest and low- 

 est points. They represent the progress of the 

 yield for the best and worst localities. An in- 

 termediate curve was also drawn for quality II. 



The curves were drawn first for the yield per 

 acre including the bark, and the values at the 

 different ten-year periods were entered in yield 

 tables, beginning with 30 years. 



Curves for the yield per acre of Pine, ex- 

 cluding the bark, as well as curves for the 

 yield of merchantable cubic and board feet, 

 were also constructed. 



The difference in the volumes for successive 

 years in a given quality is the amount of wood 

 laid on from year to year, or the current an- 

 nual increment. The volume at a given period 

 divided by the age is the mean annual incre- 

 ment. These values have been computed and 

 are given in the yield tables. It wiU. be seen 

 that the mean annual increment culminates 

 much later than the current annual increment, 

 and further, that it culminates at a point where 

 the two are equal. The current annual incre- 

 ment is at first very small, then rises rapidly to 

 a much higher point than the mean annual 

 increment ever reaches, and at last falls again. 



