Grades of Hardness, 101 



GRADES OF HARDNESS. 



It is not possible to express in words that which is commonly 

 understood by the term " Hardness," chiefly because there is no 

 measuring instrument which is free from serious deficiencies. We 

 are therefore compelled to rely upon the evidences of our senses. 

 As these vary in different individuals, and as the wood of different 

 trees of the same species, or even parts of the same tree vary within 

 wide limits, it is obvious that a scale can be only approximately 

 correct. The term "hardness" is also a loose one, but the more 

 correct phrase, " resistance to impact," while truly expressing the 

 :sense in which the former term is used in this book, is objectionable, 

 inasmuch as it implies an accuracy which is not attainable at the 

 present moment. I have been prevented from carrying out a 

 design for an instrument which will enable me to express the 

 resistance to impact in figures (cf . 27 a., p. 283) by the expense. I 

 hope that I shall be able to complete it in the near future. 



In default of anything better, I have grouped the woods of this 

 -collection in eight grades, adding a number of well-known com- 

 mercial woods for comparison. The eight grades correspond with 

 hose of Noerdlinger, who was the first to make use of this scheme. 



Grade 1. Excessively hard. 



Hackia, Bullet-tree, Letter-wood. 

 Lignum-vitee, Ebony. 



Grade 2. Extremely hard. 



Arrewewa, Bania, Booroohada, Dukalaballi, Greenheart, 

 Kakaralli, Kautaballi, Kumara, Marci-balli, Mora- 

 balli, Morakokuru, Saka, Sikki-sikki-danni, 

 Tibikushi, Tooroo Palm, Wadaduri, Wamara, 

 Yawaridanni. 



Boxwood, Lilac, Jarrah, Karri, Blue Gum. 



Grade 3. Very hard. 



Barrakarra, Brown and Yellow Cirouaballis, Eura-balli, 



Hymarakushi, Kabukalli, Mora, Phokadie, Simiri> 



Wallaba, Waranana. 

 Whitethorn, Blackthorn, Persimmon. 



Grade 4. Hard. 



Assapookoo, Barata-balli, Dakama, Hiawao-balli, Hoorihee, 

 Howadanni, Irriariadanni, Itikabpuraballi, Kokeeru, 

 Mora-bucquia, Pakoorie, Sebadanni, Sirribidanni. 

 Hornbeam, Elder, Yew, Laburnam. 



Grade 5. Rather hard. 



Kretty, KooroobovilH, Purpleheart, No. 73. 

 Ash, Holly, Plum, Common Elm. 



