Drying of Timber. 



7 5 



rather abruptly into a straight line. The curve for the radial face is 

 always the lowest, but the tangential curve of loss is always close to 

 it. The tangential curve is above the radial, not below, as indicated 

 by the statement of Wagner. The general equation to the curves is 



OAK. 



♦« 



n 















n 





IvA 



NIVI 



Ut. 















__ 







__ ■ 









/ 



^ 















r,0ii 



^ 







■z:zi 



— 









^ 













/ 



/ 









^ 



,^ 



^ 



_JJ. 



jliti'-' 



'^ 























so 





/ 



■ 







^ 



^ 



r- 

































/ 





y 



y 



^ 





































f( 



/ 



^ 



^ 











... 

































r 



y 





































^IC 



,5 







r 







1 







^ 4 





' 3 

























1 















o 



3 



(5 





"o 





o 



6 



6 ' 



7 







86 







IK 



Time in days 

 CUBVKS OF Loss OF MoiSTURK FROM THE TrANSVBKSK TANGENTIAL AND RaDTAL 



Faces of Cubes of Wool*. 



l=atb where I is the loss hi weight in grams in time, " t," '* a " is the 

 loss for the first day, " f the time in days, and " Z> " the index varies 

 in value from unity to -5, but is constant for any one curve, provided 

 the conditions of drying are kept constant. The transverse curve has 

 the greatest "a" value, and the greatest value for " ?>." When " b" 

 is unity, the curve is a straight line, and when -5 it is a parabola. 

 The radial curve approaches a parabola, while the transverse curve 

 approaches a straight line. The curves of loss for both softwood and 

 hardwood cubes are similar. The transverse face of pine, as stated 

 by Wagner, loses moisture, relatively just as readily, when com- 

 pared with the radial, as does that of a hardwood. Hence, we are 

 compelled to assume that the cause of this differential loss from the three 

 faces is due to the structure of the wood itself. Water is lost most 

 readily in the direction in which water moves in the living tree, 

 Again the tangential face loses more moisture in a given time than 

 the radial face. Abutting on the tangential face are the transverse 

 sections of the medullary rays. Hence a tangential face is a complex 

 of longitudinal sections of fibres and of transverse sections of medul- 

 lary rays. If an isolated fibre of wood be examined in polarised light 

 it will be found to give straight extinction. Transverse sections of 

 fibres, however, do not give straight extinction. If an isolated medul- 

 lary ray cell be examined in polarised light, it will be found that its 

 length in the radial direction gives straight extinction. This leads 

 us to conclude that the micellae of the fibres and of the medullary ray 

 cells are arranged parallel to the length of the cell. 



Now moisture finds its readiest movement, when the tree is living, 

 along the cell walls in the direction in which the micellae are 

 arranged. Were it not for the medullary rays, the tangential face 



