PHYSICAL PROPERTIES. 47 



2. Lustre. 



All woods can be rendered lustrous by polishing, but natural 

 lustre renders certain woods, such as satinwood, commercially 

 valuable. The radial section is the best for exhibiting lustre, 

 as it shows the widest sections of the medullary rays (silver- 

 grain), as in oaks, planes, beech, etc. The woods of the sweet- 

 chestnut, ash and hornbeam, have no silver-grain. Maple- 

 woods have a silky lustre on the radial section, and coniferous 

 woods approach them in this respect. There is no lustre in 

 the wood of any species of Pirns. 



3. Scent. 



Tannins, fatty oils and ethereal oils act as bearers of scent 

 in wood ; by boiling woods slowly the scents are isolated, the 

 more rapid the boiling, the more scent comes off with the 

 water-vapour, while by heating and drying either in the air 

 or artificially, the exhalation of scents is favoured. But after 

 as much of the water as possible has been evaporated, the 

 scent still continues, until in time the wood becomes scentless. 

 Even in old pieces of wood, by cutting and exposure of fresh 

 parts, the typical scent is again emitted. 



All species of wood possess a characteristic scent by which 

 the genera and species may be identified, but a description of 

 their scents can be attempted only by comparing them to 

 well-known scents, e.fj., the tannin-like scent of oakwood, 

 the turpentine scent of conifers ; the varieties of scent 

 of turpentine characteristic for different species cannot be 

 described. Excluding conifers, the turpentine and resin of 

 which is of commercial importance, the woods of Laiu'tn-cdc 

 (bay-tree) and the camphor trees (Cinnamonium Camphora of 

 Japan), also Dryobalanops Camphora, a dipterocarp from 

 Sumatra, are rich in agreeably-scented oil and yield commer- 

 cial camphor. Camphora glanduliferum from Assam is also 

 highly scented with camphor. Sandalwood oil is valu- 

 able. All wood-scents are obtainable by distillation, but 

 usually in such small quantities as to be of no commercial 

 importance. 



Every wood loses its typical scent when it is attacked by 



