5t TKcuxicAL i'i;{)i'i:i;Tii-:s uf wool*. 



close-grained woods shrink more than light woods, and most 

 broad -leaved woods shrink more than conifers ; but there are 

 exceptions to this rule, as may be readily imagined from the 

 great variability in the specific gravity of woods. It may, however, 

 be confidently asserted for any species that the heaviest wood 

 shrinks most. 



Nordlinger gives the following uccount of shrinkugo by volume 

 of air-dric'd W(Kjds : — 



Most shrinkage (5 to 8 per cent, of the green wood) : walnut, 

 lime, beech, hornbeam, elm, sweet chestnut, wild-cherry, Turkey 

 oak, birch, alder ('?), apple. 



Moderate shrinkage (3 to per cent, of the green wood) : 

 Maple and sycamore, black pine, Scotch pine, poplar, yew, horse- 

 chestnut, ash, aspen, oak, robinia. 



Least shrinkage (2 to 3 per cent, of the green wood): Wey- 

 mouth-pine, spruce, larch, silver-fir. 



R. Hartig gives the following shrinkage for air-dried wood : — 



The narrow-ringed porous wood of the sessile oak does not 

 shrink so much as the broad-ringed heavy wood of the pedun- 

 culate oak, and the former is therefore more suitable for furniture, 

 machine-frames, c'tc. than the latter. 



Narrow-ringed sprucewood from the Alps shrinks much less 

 than the softer sprucewood from lower levels, and the same holds 

 good for larcwhood. The more resinous a wood, the less it 

 shrinks (Mayr). 



Wood shrinks unevenly when cut in different directions : it 

 shrinks least along the grain, and for ordinary purposes this 

 slirinkage may be neglected ; it is more considerable and may 

 extend to 5 per cent, of the radial length, along the medullary 

 rays, and shrinkage is greatest and may attain 10 per cent, along 

 the annual rings, i.e. the circumference of a log. Elxner states 

 that beechwood from the stem siirinks twice as much tangeu- 



