FORMATION OF WOOD 279 



Stone gives eight grades of hardness as 

 follow : — 



1. Excessively hard. Lignum Vitae, Ebony. 



2. Extremely hard. Boxwood, Lilac, Jarrah, 



Karri, Blue Gum. 



3. Very hard. Whitethorn, Blackthorn, Per- 



simmon. 



4. Hard. Hornbeam, Elder, Yew, Laburnum. 



5. Rather hard. Ash, Holly, Plum, Common 



Elm. 



6. Firm. Teak, Chestnut, Beech, Walnut, 



Apple, Oak. 



7. Soft. Willow, Deal, Horse Chestnut, Alder, 



Australian Red Cedar, Birch, Hazel. 

 English Cherry, Canary Whitewood. 



8. Very soft. White Pine (American), Poplar, 



Lime, Sequoia. 



Colour in many cases is a useful guide to the 

 identity of the wood ; the rich brown of the 

 Walnuts, for instance, renders them distinct 

 from all other woods. In many cases, however, 

 the colour even of sound wood is variable ; 

 there are for instance at least four varieties of 

 the Locust Tree or False Acacia {Rdbinia 

 psevdacacia) (Fig. 23) ; one variety, and the 

 best, is red, another is green, another black and 

 yet a fourth yellowish. 



Neither the colour, nature of solution, colour 



