On Preventing the Decay of Wood . 32$ 
that the wood so decaying has probably been cut in the 
spring, when the sap in the alburnum was not only abun- 
dant, but of a saccharine quality; which, in combination 
with the vegeto-animal substance or gluten, disposes it to 
run with unusual readiness into destructive fermentation. 
In some trees, as by more particular custom the oak, the 
bark is a very valuable article of commerce, and is found 
not only to quit the tree more readily, but to contain a 
larger proportion of tan in the spring, when the sap is 
rising, than at other seasons. Hence an old act of Par- 
liament, now in force, ordains that all oak, except for the 
purpose of building, shall be felled in the spring. Whe- 
ther doors, posts and rails, paling, barrel staves, &c. 
come under the denomination of building, it may be diffh 
cult to say; but it seems at first view highly to be lament- 
ed, that any law should impose an obligation to destroy a 
valuable species of property. It would indeed be mat- 
ter of peculiar regret, if an impolitic and avaricious spi- 
rit should induce the owners of oak forests to extend the 
same principle to the timber employed in the construc- 
tion of great machines, and more especially the British 
navy. 
Yarious means have been employed in order to remove 
the tendency to the dry-rot in trees so felled. Thus they 
have been long exposed to the rain, or steeped, or even 
sometimes boiled in water, and then dried by artificial 
heat. These means do not however appear to have been 
successful in entirely washing out the fermentible sap, 
which therefore makes them much more subject to the 
decay of which we are treating. It may however still 
be doubted, whether it acts in any other Avay than by fur- 
nishing a disposition, which requires to be called into 
action by the same cause which operates in all other 
eases, moisture, 
Vol. xr. 
s s 
