128 



PROPERTIES OF TIMBER 



resilience of the wood of certain types of Willow is responsible 

 for their use in the manufacture of cricket-bats, whilst the ancient 

 esteem of Yew (Taxus baccata) for bows, and the modern use of 

 Ash for aeroplane-construction, are the outcome of the elasticity 

 and toughness of these woods. The elastic limit of Ash is only 

 reached under a strain of about 5,000 Ib. per square inch as com- 

 pared with 3,500 Ib. for Douglas Fir. Such qualities are probably 

 not only the result of length of fibre, but also one of physical or 



FIG. 62. Transverse sections of the secondary wood of the Sycamore (Acer 

 pseudoplatanus) (right) and the Oak (Quercus) (left). Note the fibres 

 (/), which are much thicker- walled in the latter than in the former. 

 m, medullary ray ; V, vessels. 



chemical constitution of the xylem walls. Liability to splitting 

 is often due to a large size of the constituent elements, and it is 

 the reverse condition which renders the timber of the Hornbeam 

 (Carpinus) so suitable for cog-wheels, etc. The " figure " of 

 timber, to which many woods owe their value in cabinet-work, 

 is dependent on the direction of the fibres and the prominence 

 of the medullary rays when cut in certain planes. 



To render timber suitable for use, the cut log needs to undergo 

 a process of seasoning, which involves the drying out of the 



