CHAPTER XIT 
HOW WOOD IS PRESERVED 
OnE of the greatest drawbacks to the extensive use 
of wood is that while it is easily worked and the first 
cost is comparatively slight, it may be expensive in the 
long run because it is subject to decay, especially when 
used in contact with the ground. 
Reasons for Decay.—Decay in wood as in any sub- 
stance is due to the action of bacteria and fungi and as 
a rule timbers containing considerable moisture and 
sugar are much more subject to disintegration. The 
agencies causing decay must have food, oxygen, a cer- 
tain amount of heat and water in order to live and 
thrive, and if any one of these necessities is removed 
from the wood, decay can be postponed for a long time 
or prevented altogether. If a fence post has been thor- 
oughly seasoned before being put into the ground it will 
last much longer than one which was used green, as the 
moisture in the freshly cut stick is favorable to the 
action of the bacteria and fungi. If air is cut off from 
timber the agencies causing decay cannot work and that 
is the reason the oak found in English bogs and the pile 
foundations of the Swiss lake dwellings are in such a 
splendid state of preservation. 
Methods of prolonging the life of wood have long 
been known, for in the earliest times the Ancients 
succeeded in preventing decay by impregnating timber 
with cedar oil or coating their statues with oils or by 
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