86 TECHNICAL I'KOPEKTIES OK WOUl). 



It is also evident that the half-dried ^vood used in buildings, 

 wbeu bouses are cheaply constructed, cannot be durable. 



It is for engineers to insist on being supplied with thoroughly 

 seasoned timber, and wood-merchants will then take the neces- 

 sary trouble to provide it. 



4. Utilization of the Wood. 



The external influences, or environment in which wood is 

 placed, must have very great effect on its durability. Thus, 

 there is a great difference when wood is used in wet or dry 

 places, and whether it is more or less subject to free air-currents 

 and heat, or more or less in contact with the ground. 



(a) Wood used in Dry Places.— Wood used in places which are 

 nearly or completely dry is very durable, for moisture is neces- 

 sary for the development of decay. This is clearly seen from 

 the condition of wood in the interior of buildings, where furni- 

 ture, carvings, mummy-cases and otiier wooden effects of the 

 most various kinds remain unimpaired for centuries, and even 

 thousands of years, without showing the least decay of their 

 woody fibres. If we exclude the danger of attacks by insects, 

 and only consider that by fungi, wood of all species is extremely 

 durable when kept in dry places, even that of beech and birch, 

 which are not otherwise considered durable woods. 



When, on the contrary, utilization in dry places means that 

 instead of being kept in rooms artificially heated during winter, 

 wood is used in places which directly communicate with the 

 external air and its varying humidity, such as sheds, or open 

 garrets, it is evident that wood-destroying organisms may 

 develop, and the conditions of durability are \ery different from 

 those in the former case. 



It is matter of everyday occurrence that wood merely sheltered 

 from above may become rotten, and that in such cases firewood 

 may lose a part of its heating-power, and timber its strength 

 and elasticity. 



Grubs and imagos of different insects also destroy wood, and 

 wood in the dry state is most subject to this form of destruc- 

 tion. Without including grubs which destroy the cambium 

 between the wood and bark, and which may be brought from 



