278 TIMBERS AND THEIR USES 



grouped roughly in six grades, as quoted by 

 Professor Boulger. 



1. Hardest, sucli as the Ironwood of India, 



Mesua ferrea, wliicli turns the edge of 

 almost any tool, and Lignum Vitse 

 (Guaiacum), which requires 793 kilo- 

 grammes to produce the standard in- 

 dentation. 



2. Very hard, requiring more than 3,200 lbs. 



per square inch, such as Hickory and 

 good Oak and Elm. 



3. Hard, requiring from 2,400 lbs. to 3,200 



lbs., such as Ash, Walnut, Beech, Holly, 

 Sycamore and Sweet Chestnut. 



4. Medium, requiring from 1,600 lbs. to 2,400 



lbs., such as Douglas Fir. 



5. Soft, requiring less .than 1,600 lbs., such 



as the majority of coniferous woods, 

 Pine, Spruce, Cedar, Poplar, Linden and 

 Horse Chestnut. 



6. Very soft, such as the so-called Cotton 



Tree of India {Bombax malabaricum), 

 which is so soft that a pin can readily 

 be driven into it with the fingers. 



" Hardness and density or weight to a great 

 extent vary together. They also increase from 

 the base of a stem up to its first branch and 

 decrease from that poijit upward." 



