WHEN TO HARVEST 55 



tree with a diameter of five inches at the stump contains 

 only one fourth as much wood as one of ten inches, for the 

 squares of their diameters are in that ratio; the number of 

 square inches in area of each proves the fact, and the same 

 law applies to all other dimensions. For instance : a tree 

 twenty inches in diameter contains 1.77 times more wood 

 than one fifteen inches, for the square of their diameters 

 and the number of square inches in their areas are in that 

 ratio. The application of this rule gives an easy and cer- 

 tain method of determining the relative values of different 

 trees. One has only to square their diameters and divide 

 the greater by the less to determine it. An examination 

 of the table shows how rapidly the available wood of a tree 

 increases by age and the importance of allowing a tree to 

 enlarge its diameter. The table is limited to eighty years, 

 for the annual growth usually begins to lessen then, but 

 the principle is applicable to any diameter, irrespective of 

 age. 



(2) Lumber manufacturers well know that the relative 

 proportion of waste in slabs and edgings is much greater in 

 a small than in a large log. Most of them use rules and 

 tables giving the number of board feet that can be cut 

 from logs of given sizes, but these take into consideration 

 all kinds of waste, such as crooks, lack of cylindrical form 

 of logs, and other causes, and hence such will not serve 

 our purpose here, where we are discussing only the relative 

 waste arising from different sizes. It is a mathematical 

 fact that the bark surface on a small log is proportionally 

 greater, when compared with its contents, than on a large 

 log. The ratio of waste between small and large sizes is 

 the reverse of that of the wood contents. The circumfer- 

 ence the bark surface of a log twenty inches in diam- 

 eter is only twice that of one ten inches, while the con- 

 tents the wood of the twenty-inch log is four times 

 that of the ten-inch one, which fact gives an approximate 

 idea of the relative waste. 



(3) As the ratio of waste lessens as the tree advances in 



