Structure and the Physical Properties of Wood. 351 



tion in their thermo-conductive and resonant properties ; and the 

 difference in the former is greater or less as the two latter differ- 

 ences are greater or less. 



Hence a definite relation may be established between the differ- 

 ent pluenomena described ; and this is true to such an extent, that 

 the knowledge of one of them, e. g. the mechanical or state of co- 

 hesion,is sufficient to deduce the others, those of warmth or resonance. 



Thus, merely to adduce one example, especial experiments had 

 shown that in petrified woods a difference of structure in the 

 directions parallel with, and perpendicular to, the direction of 

 the grain had been preserved; and, in fact, the thermal curve 

 was an ellipse whose major axis was parallel to the fibres. As 

 in the petrified example this difi"erence in mechanical structure 

 was much less than in the living wood, so also, while in the 

 living Conifer the ratio of the axes was as 1 to I'SO, in the pe- 

 trified specimen it had sunk to 1 to 1-13. 



The following Table contains the names of the woods examined, 

 arranged according to the groups mentioned : — 



Group I. 

 Ratio of the axes of the thermal ellipse 1 to 1-25. Mean ratio of 



deflection 1 to 5'0. 

 Acacia. King-wood. 



Box. Satin-wood. 



Lignum-vitae. Salisburia (Gingko). 



Cypress. 



Group II. 



Ratio of axes of thermal ellipse 1 to 1-45. Mean ratio of deflection 



1 to 8-0. 



Elder. 



Alder. 



White Thorn. 



Arbor vitse. 



St. Lucien wood. 



(jymnocladus canadensis. 



Beech (2 species, white and red) . 



Plane. 



Elm. 



Oak (two species). 



Ash. 



Maple. 



American maple. 



Cedar of Lebanon. 



Australian cedar. 



Mahogany. 



Palisander. 



Ebony. 



Palm. 



Rosewood. 



Snake- wood. 



Zebra-wood. 



Purple-wood (Amaranthus) . 



Settin. 



Coromandel wood. 



Angica-wood. 



Cocoa-wood {Gateado). 



Apple. 



Pear. 



Cherry. 



Plum. 



Sandal (red). 



Caliatour. 



Costarica (red wood). 



Bimas sapan. 



Cuba (yellow wood). 



Viset (yellow wood). 



Campeachy blue wood. 



Tabasco blue wood. 



Domingo blue wood. 



