154 THE BOOK OF FORESTRY 
any place where the impregnation has been slight may 
be attacked later with agencies of decay. 
The toredo, a boring mollusk found in tropical waters, 
has been found to attack creosoted piles only where 
blows of a sledge had dented the wood and diminished 
the thickness of the treated layer. 
If care is used in controlling the temperature and 
strength of the solution used, treated timbers will be 
fully as strong as they were previously. Under new 
methods, especially those in which creosote is used, 
there is no chemical reaction between the wood fibers 
and the preservative; the creosote simply forms a film 
around the fiber. The amount of heat used in this 
process can be carefully regulated but the amount of 
moisture contained in the treated timber is of much 
more importance. Creosote retards both the evaporation 
and the taking up of water and therefore, if thoroughly 
seasoned wood is treated, it will be practically im- 
possible to take up any water afterward. But if the 
wood is not thoroughly seasoned before treatment rapid 
disintegration may take place. This is quite similar 
to the dry rot that is found shortly after partially sea- 
soned or green wood has been painted. 
Treatment with zine chloride may produce unsatis- 
factory results, especially if the timbers are not 
thoroughly dried before being used. However, there 
seems to be a chemical reaction in this case, for if too 
strong a solution is used, the wood fibers are corroded 
and a noticeable loss of strength occurs. 
The chemical treatment of wood to prevent decay 
is long past the experimental stage in this country and 
it is a practice certain to increase. In view of the 
fact that decay alone is responsible for seventy per cent 
of all the destruction of timber, economy demands that 
