Structure and the Physical Properties of Wood. 349 



their planes, and then covered as uniforinly as possible with a 

 coating of stearine. A hot wire, exactly fitting the bore, was in- 

 troduced into the latter and continually turned round during the 

 experiment. By this means the coating of stearine around the 

 orifice was melted ; but, as we should expect, not in concentric 

 circles, but in elliptic zones, whose major axes invariably coin- 

 cided with the direction of the grain. The great difi^erence in 

 the behaviour of diff'erent kinds of wood (about eighty sorts were 

 examined) under these circumstances is at once apparent. With 

 some the ellipses are tolerably circular, by others more elongated, 

 while by others, again, the major axes are so extended as to be 

 nearly twice the length of the minor ones. The excentricity of 

 these ellipses, which furnished a graphical expression for the 

 conductive power of the wood in the directions between which 

 the structural difierence was greatest, made it possible to divide 

 the different kinds of wood into four distinct groups. In the 

 first, the ratio of the minor to the major axis of the ellipse is on 

 the average as 1 to 1"25. To this group, Acacia, Box, Cypress, 

 King-wood, &c. belong. In the second, and by far the most nu- 

 merous group, containing Elder, Nut, Ebony, Apple, several 

 dye-woods, &c., the mean value of this ratio is 1 to 1"45. In 

 the third group, to which Apricot, Siberian Acacia, Brazil 

 wood. Yellow wood from Puerto Caballo, &c. belong, the ratio 

 is as 1 to 1*60. In the fourth group it is as 1 to 1"80, and to 

 this division belong Lime, Tamarind, Iron-wood, Poplar, Sava- 

 nilla (yellow), &c. Hence the conducting jmiver of all woods in 

 the direction of the fibre exceeds that in the perpendicular direction 

 hy no means in a constant mamier, but in one which dep)ends upon 

 the nature of the ivood. This superiority is in the first group so 

 small, that the warmth in the direction of the fibre traverses a 

 path only a quarter more in length than that traversed in the 

 same time in a perpendicular direction. In the last group, on 

 the other hand, the length of the path in the first direction is 

 about twice that in the perpendicular one. 



In order to investigate the relations of resonance, two rods 

 were cut from each kind of wood, — the one being taken in the 

 direction of the grain (Langholz), the second perpendicularly 

 across it (Hirnholz). On suspending these rods freely (their 

 length was 470 millims., breadth 20 millims., and thickness 

 8 millims.) and striking them with a stick, the piece cut with 

 the grain always gives a more sonorous tone than the correspond- 

 ing cross-grain piece. Nevertheless the difference of resonance 

 in the tones of the with- and cross-grain pieces of one and the 

 same wood, of the first of tlic groups described (say beech), is 

 unmistakeably less than the diflercnce between the tones of the 

 with- and cross-grain pieces of any member of the second 



