r.ELATIOXS OF WOOD TO WATf^R. 49 



stronger than when grown on warm aspects ; also that spruce- 

 wood is stronger when grown above 1,300 metres (4,225 feet), and 

 silver-fir wood below that altitude. The larch in the Bavarian 

 Alps, according to Bauschinger, resembles the silver-fir in this 

 respect. In different trees individuality is a most important 

 factor of strength, as of all the economic qualities of timber. 



It is customary to rate wood felled in December as strongest 

 and that felled in March to have lost one-third of its strength, 

 but such assertions should be accepted with caution. 



(d) Comparative Stren^h of Different Species of Wood. — 

 Authorities still dilier as regards the comparative strength of 

 the different woody species. 



Bauschinger classes conifers grown in Upper Bavaria as 



follows : — Atmospheres. 



Transverse strength of larch . . . .545 — 745 



spruce . . . 365—690 



,, ,, Scotch pine . . 245 — 705 



silver-fir . . . 485—570 



,, ,, Cembran pine . 365 



,, ,, Weyraouth-pine . 250 — 290 



It should be noted that the Scotch pine was least at home 

 in the locality. 



[Tredgokl* places the broad-leaved trees in the following descend- 

 ing order of transverse strength : — • 



Oak. White Poplar. Birch. 



Ash. Common Elm. Sweet Chestnut. 



Beech. Sycamore. Black Poplar. 



Robinia. Alder. Willow.— Tr.] 



Builders practically assign the greatest transverse strength to 

 oak, then to the indigenous conifers, and then to ash. Beech, 

 birch and alder, are considered by them as weak timbers. 

 In order to produce strong building-timber, the same rules must 

 be followed which have been already laid-down under the head 

 of elasticity. 



Section IX. — Eelations of Wood to Water. 



Wood is rarely used so that it will not be exposed to moisture 



in some form or other, and hence the effects of water on wood 



* Tredgold's Carpentry b}' Hurst, 1871. 

 VOL. V. " E 



