DURABILITY. 97 



steaming wood for chairs, banisters, curved planks used in 

 carriages, ships and barges, musical instruments, etc. Frozen 

 wood is hard and brittle. 



When resin (semi-liquid turpentine) replaces water in wood, 

 pliability is diminished, wood charged with rosin or colophany 

 (oxidised turpentine) becomes harder, the longer the rosin has 

 been in its tissues. 



The colouring-matter in heartwood diminishes the pliability 

 of wood. 



The following list shows that pliability depends greatly on 

 species, but in practice there is much difference of opinion on 

 this subject. 



Si'i;cn;.- AKI;AN<;I;I> ACCORDING TO THKIU PLIABILITY. 



Pfeil. 



Other InvtM 



Hickory. 

 Ash. 



Elm. 

 Hornbeam* 



I, arch. 



i 'iii' 1 ami Spruce. 

 Oak. 



Birch. 



Ash. 



Will 



Poplars. 



Cork Kim. 



Bickory. 



Species "f I'irus. 



Cuppi r various broadleaved trees. 



Suppressed Spruce. 



5. Durability. 



Durability is a measure of the time during which wood 

 remains sound. In using and storing wood it appears that 

 the durability of any species of wood varies remarkably. For 

 instance, beechwood, when made into furniture that remains 

 inside our houses, may last for centuries, but the same wood, 

 when exposed to moisture from the soil, rots in from three to 

 five years, while under water it can be kept sound for decades. 

 As a rule we understand by the term durability a measure 

 of the duration of wood that is used more or less in contact 

 with the ground, as for posts or railway-sleepers. 



The various forms of decay in wood are, as follows : 



Greyness. Wood that is not exposed to ground-moisture 

 but to atmospheric influences and precipitations, variations of 



F.U. H 



