PROPERTIES OF WOOD 



A Chapte;r From Lucien Chancerkl's Botanique Forestiere 

 Translated by Winifred Whaley 



The relation between the biological properties of wood on the one 

 hand, and its physical, mechanical and chemical properties on the other, 

 is often neglected both by biologists and engineers ; the former because 

 of lack of knowledge of mechanics, the latter because of lack of knowl- 

 edge of biology. The following views on properties of wood from 

 the standpoint of a biologist may therefore be of interest. They are 

 reproduced almost literally from "Botanique Forestiere," by Lucien 

 Chancerel. 



Color. — The color of woods varies greatly. In some species the 

 heart and sap wood are colored differently so that they can be dis- 

 tinguished in this way. In others this distinction is not apparent. The 

 polishing qualities of woods are also very variable; in some the polish 

 has a satiny appearance, in other variegated. 



Odor. — Woods have distinctive odors due to essential acids or oils, 

 which are often characteristic of a species. Odor also often indicates 

 alterations in the wood, for instance, the presence of worms. 



Hardness. — Hardness is the quality of woods which measures the 

 resistance they offer to usage, splitting, compression, shock, and the 

 penetration of nails. The following degrees of hardness may be dis- 

 tinguished : hard woods, such as oak and hornbeam ; semi-hard woods, 

 as birch and alder; soft woods, as basswood, poplar and willow; and 

 resinous woods. The hardness of woods is in proportion to their 

 specific gravity. 



Density. — Density in broadleaf woods, like hardness, is generally in 

 direct proportion to the thickness of the annual rings. This is explained 

 by the fact that in broadleaf species growth produces mainly the ele- 

 ments of autumn wood, which are the thickest and most lignified. On 

 the other hand, density and hardness in resinous woods are in inverse 

 ratio to the thickness of the annual rings, because in these woods growth 



Precis de Botanique Forestiere et Biologic de I'Arbre by Lucien Chancerel. 

 Paris, 1920. Pp. 145-157. 



414 



