PITH, OR CENTRE. 



look for the pith or centre of the stem, or if that 

 has been removed by the conversion of the tree 

 for the innermost, or oldest layer of heart-wood, in 

 the plank or board, as that will be the inside of it. 

 If this precaution is disregarded, the innermost or 



FIG. 



earlier layers of wood lift and shell out, after exposure 

 for a time, in shreds and strips, the cohesive properties 

 of the ligneous layers having been destroyed by the 

 action of the atmosphere. Fig. I shows the plank 

 properly fixed, with the inner or earlier layers of wood 



FIG. 2. 



against the beam, in which position it is impossible for 

 them to separate. Fig. 2 shows the plank improperly 

 fixed, with the outer, or later layers of wood against the 

 beam, in which position the earlier layers are very liable 

 to lift, or shell out, destroying the evenness of surface ; 



