90 TECHNICAL rROPERTIES OF WOOD. 



Wooden piles used iu harbours, etc., may be protected by being 

 creosoted, but this is serviceable only when the wood is thoroughly 

 saturated with creosote ; as coniferous wood imbibes creosote 

 Ijetter than oakwood, it is better when creosoted than oakwood 

 for use in dams and other harbour-works. Attempts have been 

 made to protect piles in sea-water by studding them with broad- 

 headed nails, but the little teredos force their way into the wood 

 between the heads of the nails. In the years 1827 and 1859, 

 when the rainfall was very slight and the Dutch canals near the sea 

 coast became very salt, it was found that all the piles supporting the 

 dams along the Dutch coast were bored by teredos. A Commission 

 was appointed in Holland, in 1859, to euijuire into the causes and 

 possible remedies of this damage, and from its report, written 

 by V. Baumliauer and quoted in Ratzeburg's Forstinsectenhinde (by 

 Judeich and Nitsche, 1889), the above remarks have been taken. 

 It is also stated by Nanqiiette,* that when timber is stored in 

 sea-ports for ship-building and harbour-works, it should either be 

 kept in banks of mud, or in tanks in which sufficient fresh-water is 

 mixed with sea-water, so as to render it less saline than is necessary 

 for the life of the teredos. — Tr.] 



(c) Long-continued Exposure to Alternations of Damp and Dry- 

 ness. — The durability of woods is greatly reduced when it is 

 exposed to alternations of damp and dryness for any prolonged 

 period, for it is then uninterruptedly in contact with air and 

 moisture, which greatly favours decay. All timber used in water- 

 works and canals — such as piles for bridges ; wood-work in 

 canal-locks, and for maintaining the banks of a stream ; wooden 

 weirs ; the staves of casks ; ships, boats and many other con- 

 structions and implements — is specially liable to decay. In all 

 these cases experience shows that the wood decays all the more 

 rapidly, the warmer the air-tcmpcrature of the locality. Thus, on 

 northern aspects, in cold valleys, in high altitudes and latitudes, 

 the durability of timber is much greater than on southern aspects 

 and in warmer localities. In such unfavourable localities, 

 timber exposed to rapid alternations of moisture and dryness 

 may last for only a few decades, or even a few years, according 

 to the species used. Such an employment of wood is the best 

 test which can be found of its durability for any purpose 

 whatever. 



* E-rploHation dcs JJois, 1SG8. 



