72 THE WHITE PINE 



The yield tables are based upon the valuation 

 surveys given in the summary above. It would 

 have been very difficult and equally undesirable 

 to construct tables showing the actual yields 

 measured per acre at the different ages, because 

 the areas assessed were either not fully stocked 

 by nature or had been thinned by fires or inju- 

 dicious cutting, or else they contained a large 

 percentage of other species in mixture. Conse- 

 quently the results at different ages would have 

 been more influenced by the degree of density 

 than by any differences in the localities. The 

 yield tables are therefore constructed to show, 

 not the actual yield per acre as found in the 

 valuation surveys, but the yield of acres fully 

 stocked with pure White Pine. It is easy to re- 

 duce the figures to correspond with any less 

 degree of density, simply by multiplying them 

 by the decimal which expresses it. Thus the 

 yield of an acre only half stocked with Pine 

 would be found by multiplying the figure in the 

 table by 0.5. 



In the preparation of the tables the yields of 

 the acres were divided by the respective density 

 factors, and the yields for fully stocked acres 

 were thus obtained. The latter were then plot- 

 ted upon cross-section paper, on the horizontal 

 lines or abscissae of which the number of years 



