PRACTICAL HINTS 



vary much in the same proportion, as all depend upon the last. 

 Exceptions there are in abundance, but they can generally be 

 explained by variations in the structure or in the secretions. 

 The hardness therefore is just as variable as the weight, and 

 the senses are almost the only guide. The estimation of this 

 quality is complicated by the fact that several properties or 

 combinations of them are classed under one general term. 

 The resistance of a wood to the saw is not of the same nature 

 as that to the plane or knife, or to a pointed instrument like a 

 nail, or a blunt one such as a hammer, or again as the resis- 

 tance to wear by friction. There is the flinty hardness of 

 Lignum-vitae (Guaiacum), the brittle hardness of Ebony, the 

 tough hardness of Boxwood, due to the impressions made upon 

 the senses by other qualities such as elasticity, fissibility, tenacity 

 or toughness, in addition to hardness per se. 



Amongst other features we must not overlook the compactness 

 of grain, i.e. the density of the woody ground-tissue (wood- 

 fibres), which contributes to our sense of the smoothness of the 

 wood and to its coldness or warmth to the touch. Some woods 

 feel like marble, others like wool. Further, we have often strong 

 evidence from the smell or taste, so much so that we can tell 

 Teak or Pencil Cedar with the eyes shut. The smell of the 

 former is truly abominable while that of the other is delightfully 

 sweet. It is said that fresh Teak is " fragrant " ; would it were 

 so in the seasoned timber. The Pencil Cedar combines its 

 sweetness of smell with sweetness of taste, as all who chew 

 their pencils know. At the other extreme is Quassia wood, 

 of which cups used to be turned, which imparted the bitter- 

 ness of the wood to any liquid allowed to remain in them. 

 Smell is the most fugitive of these characters and may sometimes 

 have passed away in old dry wood, but for the most part it can 

 be revived by making a fresh cut. Frequently the smell is 

 only apparent during working or becomes much more powerful 

 then. It may be accompanied by an irritating dust causing 

 violent sneezing and running of the eyes, as in the Sneezewood 

 of the Cape of Good Hope, or in a less degree in Blue Mahoe. 

 Again, some woods are aromatic when burning, quite apart from 

 the smell of the pyroligneous acid in the smoke, as witness the 

 Sandalwood of which Chinese Joss-sticks are made. Inflam- 

 mability ranges from the easily-lighted deal and Lignum- 

 vitae which will burn like a candle, to certain species of 

 Eucalyptus, Jarrah, Blackbutt and Tallow-wood of N S Wales 

 These may certainly be made to burn, but as soon as the flame 

 has gone off the carbonized remainder ceases to glow and 

 expires as soon as it is left to itself. Australians lay truly 

 that it takes three sticks of Oak to burn one of Gum (17). 



xxviii 



