262 
TIMBEE 
edges of sapwood, decay first, and whilst the top edges are 
often badly decayed, the lower edges remain quite sound, 
as the water cannot lie there. 
The reason why the floors and joists in basements, or 
over cellars, are more liable to decay than the rest of the 
timber in a building is because they are more subject to 
damp and moisture and often have not proper air currents 
round them. 
The joinings of timbers, whether notched or unnotched, 
or where one timber rests upon another so that wet or 
damp is liable to lodge, should have a good coat of Stock- 
holm tar and pitch put on hot ; this is an excellent 
preservative. 
Some recent German theory goes to show that the 
calcium bicarbonate arising from the hydrate of lime in 
mortar is probably the chief cause in the development of 
spores, as almost without exception the wood nearest to 
the walls of buildings is first attacked by rot. When 
fungus has gained access, all visibly affected parts should 
be cut away, as well as the adjoining and apparently sound 
timber for several feet round, and the brickwork should be 
well cleaned and brushed over with creosote or coated with 
good plaster. 
The most destructive agent with which the engineer has 
to contend in the case of timber structures erected in sea 
water is known by the general name of the sea worm. 
One or other of the several pests known by this name are 
found in sea water all over the world and cause enormous 
destruction. 
The Teredo Navalis, often called the " ship worm " from 
its destructive action on timber ships, as a protection 
against which they had to be copper sheathed, resembles a 
long worm, although it is really u mollusc. The animal is 
