p. Groom 33 



Set F, 



The first set of measurements, recorded in Table F, were made by 

 means of the measuring rod during the absorption of water. The changes 

 in length were too slight to be accurately estimated. On the gther 

 hand measurements of the diagonals and across the two ends were 

 possible, and evidence in favour of their substantial accuracy is supplied 

 by the fact that the widening of the board at both ends was the same 

 on the average, viz. -6375: moreover on the face y it was -65 at each 

 end, and on face Y -625 at each end. This represents a widening of 

 5-3 per cent, of the full length attained. But it must be noted that 

 when the board was first placed in water it was not sufficiently dry to 

 be in equilibrium with the atmospheric humidity of the laboratory; 

 this was proved in the second set of observations when the board was 

 dried. 



During soaking the board twisted, but the direction of the twist 

 was opposite to that of yang 1 in conformity with the fact that on the 

 two faces its exposed oblique grain ran in directions representing spirals 

 reverse in sense to those of yang 1. On face Y, the diagonal Y . Yxb 

 ran more with the grain and therefore showed less elongation (-1) than 

 did Yx , Yb (-2) which was directed more across the grain and became 

 convex. For the same reason the elongation of yx . yb (-175) was less 

 than that of y . yxb (-25). Consequently of the two superposed diagonals 

 Yx . Yb and yx . yb the former became convex and the latter concave : 

 while of the other two superposed diagonals y . yxb became convex and 

 Y . Yxb concave : the result was the above mentioned twist. Naturally 

 in subsequent drying these relations were reversed. 



Ann. Biol, ni 3 



