DIMENSIONS OF TREES. 



117 



stains, when only boiling under ordinary atmospheric pressure 

 is employed. If the liquid is pressed into the wood by pneu- 

 matic or hydrostatic pressure the sapwood of all woods absorb 

 it easily and thoroughly, especially when the antiseptic liquid 

 is pressed in through the transverse section or a hole bored in 

 the wood, and follows the course of the fibres (Hydrostatic 

 method.) The presence of vessels facilitates the absorption of 

 the liquid. The heartwood, on account of its dryness, and in 

 hardwoods because the vessels are often filled with thyloses, is 

 less absorptive ; if also the heartwood is naturally coloured it 

 will not absorb antiseptic liquids (oak, larch, and Scots pine 

 partly). The abnormal reddish colour in beech heartwood 

 also prevents impregnation. The more freshly cut the wood, 

 the more absorptive it is, but dry wood, especially of conifers, 

 takes a longer time for the liquid to pass through the walls 

 of the tracheids. [It is, however, the practice in Ireland to 

 season Scots pine railway-sleepers for twelve months before 

 creosoting them ; the sleepers then last for eighteen to nine- 

 teen years, instead of for only nine years if they are creosoted 

 immediately on arrival at the workshop. If unseasoned wood 

 be creosoted, the external layers enclose wet heartwood. Even 

 after being eighteen or nineteen years on the permanent way, 

 the sleepers creosoted after seasoning are removed solely 

 because, owing to abrasion, they become too thin (3J inches) ; 

 they are still serviceable for many years as fencing-posts. Tr.] 



8. Dimensions of Trees. 

 MAXIMUM 



