16 



PEACTICAL FOEESTEY. 



portions of the Adirondack forest, the younger spruce will grow up 

 and replace the original stand of timber in about twenty years. 

 But this will not happen unless the rules for cutting are faithfully 

 observed, nor will it happen more than once unless enough old trees 

 are left standing for seed. Such a forest may then be divided into 

 twenty parts, and the merchantable timber about 12 inches in diam- 



FiG. 8. — Mimic pure selection forest, showing mixture of ages. 



eter may safely be cut from one division every year. By the time 

 the last of the twenty divisions has been cut over, the first will have 

 upon it a stand of mature spruce equal in quantity to that of twenty 

 years before. The yield of the whole forest in spruce for a single 

 year may be cut each year from one-twentieth of the whole area. 

 If all the divisions were cut over five times in the life of a mature tree, 

 then one-fifth of the standing timber would be taken from each 

 division at each cutting. Thus, if it took one hundred years for a 

 tree to become ripe for the ax, the cutting (at intervals of twenty 

 years) would return five times during the hfe of the tree, at its twen- 

 tieth, fortieth, sixtieth, eightieth, and one hundredth years. 



This is the system of localized selection. It is simple and easy to 

 ^Pply; and even if mistakes occur they are not apt to have dangerous 

 consequences. It is very elastic and has many forms, and it is well 

 adapted to many different kinds of forest. Logging is cheap, because 



358 



