HOW WOOD IS PRESERVED 155 
this loss should be decreased. The rapid increase in 
price due to diminishing supply of the naturally durable 
woods has forced the consumer of construction timbers 
to substitute cheaper and less lasting species and this 
fact alone will inevitably result in mereased preserva- 
tive treatment. 
Costs and Effects of Preservation —When it is realized 
that at a cost of thirty-five cents for impregnation a 
railroad tie costing seventy cents will last seventeen 
years instead of seven, the economy of this practice can 
be seen and the wisdom of the American wood consumer 
in reducing the drain upon the nation’s forests by the 
use of preservatives can be highly commended. That 
timber preservation is on a rapid increase is evident 
when it is realized that during the past nineteen years 
the number of plants for the treating of timber increased 
from fifteen to one hundred and twenty-two. Of the 
present number one hundred are of the pressure cylin- 
der variety. 
During the past year nearly 80,000,000 gallons of 
creosote, 27,000,000 pounds of zine chloride and 2,500,- 
000 gallons of other preservatives such as crude oil and 
coal tar were used. Altogether 160,000,000 cubic feet of 
timber was preserved which in the form of railroad ties 
would be sufficient for a new line 1100 miles long. The 
rapid rise of the preservation industry is a striking ex- 
ample of the increasing economy which is being prac- 
ticed regarding the products of the forest. 
