14 OUR VANISHING FORESTS 



forty years, and then let us apply ordinary arith- 

 metic. A crop of 125 million ties would require 25 

 million trees; that is to say, altogether about 900 

 square miles of forest. A permanent crop of 125 

 million ties every year would require 36 thousand 

 square miles of carefully protected woodland, one- 

 fortieth of which would be cut annually and imme- 

 diately replanted. This is an area as large as the 

 whole state of Indiana, but equivalent to less than 

 one-tenth of the existing forest area of the United 

 States. 



Some such plan must unquestionably be adopted. 

 As the available sources of wood are depleted, there 

 is no doubt that tree planting on a commercial scale 

 will become general. Public interest must steadily 

 increase, and a timely consideration of the whole 

 wood problem by government and state authorities 

 will do much towards its solution, 



