p. Groom 19 



The two faces were labelled y and Y respectively, Y and Yx, y and yx 

 denoting the four corners of what may be termed the top of the board, 

 y and Y being at the same edge or corner: similarly Yh and Yxb, 

 yb and 7jxb denoted the four corners at the bottom end of the board. 

 Consequently the lengths of the board on the two faces are represented 

 by measurements y . yb, yx . yxb, Y . Yb, Yx . Yxb, of which y . yb 

 and Y . Yb represent the same margin of the board on two different 

 faces, as do yx . yxb and Yx . Yxb. The diagonals were thus Y . Yxb, 

 Yx . Yb, yx . yb, and y . yxb. 



In this cross-grained board on each face the grain runs from the top 

 towards the bottom in a direction from right to left hand, though on 

 face Y the grain is to a considerable extent nearly straight on the lower 

 (bottom) half. 



Observations. Set A (Table A), 



The first measurements of yang 1 were made on a board, already 

 partially seasoned in the timber-yard, during its drying in the laboratory. 

 As a simple measuring rod was used the longitudinal changes in length 

 were too small for accurate estimation, but the changes in length of 

 the diagonals and in width were sufficiently considerable for approximate 

 measurement and are recorded in the accompanying Table A. 



In accordance with the direction of the grain the shrinkages along 

 the two diagonals Y . Yxb and yx . yb were greater (-2 and -IS) than 

 along the other two diagonals, so that the board became concave along 

 the former pair and convex along the latter pair. The two ends of the 

 board were thus twisted so as to lie in different planes, but they never- 

 theless retained their transverse straightness approximately. 



