32 Slirhikacje, SwelUnrj, Warping of Cross-grained Woods 



Columns 4, 5, 8, 9 similarly record the deviation in millimetres of 

 the middle point of each half of the respective diagonals ; columns 4 

 and 8 denoting the half (top) towards the y . yx end, and columns 5 

 and 9 denoting the half (bottom) towards the yh . yxb end. 



Columns 6 and 10 record the amount of twist by giving the number 

 of millimetres that the end point is raised above the base line, as recorded 

 by the instrument. 



Table E shows that on June 21 the dry board was warped and 

 twisted, being on one face {y) concave along one diagonal yx . yb and 

 convex along the other, y . yxb. With the absorption of water these 

 diagonals by differential elongation lost their curvature, and were 

 almost or quite straight on June 24 and 25. As water continued to be 

 absorbed until July 5 the original curvatures of the diagonals were 

 gradually reversed, yx . yb becoming convex and y . yxb concave, the 

 reversal taking place more obviously along yx . yb (crossing the grain).. 

 During the drying from July 7 onwards (and even before this, for some 

 unknown reason, in the case of yx . yb) the curvatures gradually reverted 

 to those originally present in the dry board. 



It is worthy of note that the amounts of warp and twist were not 

 exactly determined by the amount of water contained. This fact is 

 demonstrated by comparisons between the conditions of the board on 

 June 21 and on July 16 and December 10. The greater twist and warp 

 during the final drying are probably due to the fact that the loss of 

 water was more rapid in the warm dry air of the laboratory than during 

 the original industrial seasoning of the board. This consideration 

 emphasizes the special importance of carefully regulated seasoning of 

 cross-grained woods. 



Observations on Yang 2. 



The board named yang 2 was cut tangentially and its faces were 

 lettered as in the case of yang 1 ; on one face, Y and Yx denoting the 

 top corners, Yb and Yxb the bottom corners; and on the other face, 

 y and yx, yb and yxb denoting the corresponding points, but y was 

 superposed on Y, that is to say Y and y are at the same edge of the 

 board. Thus for instance YYb and yyb represent the same side of the 

 board on the two different faces and Y . Yxb and y . yxb represent the 

 same diagonal on the two faces. 



