14 Shrinkage, Simlliiifj, Warping of Cross- grained Woods 



sold as "yang teak," but the results were not satisfactory, In-doors 

 the wood twisted as it dried; while out-of-doors when it absorbed 

 moisture yang was described as speedily showing on its surface a " white 

 growth" and as undergoing early decay. During the progress of this 

 investigation the practical problems of preventing these defects were 

 more or less solved, and a digression on the cause of the disfigurement 

 and decay out-of-doors may not be out of place. 



Submersion of yang boards under water causes quantities of white 

 substance to appear at intervals over the surface and especially at the 

 ends. This substance is mainly resin that is forced out by the sweUing 

 of the woody tissue. I examined a few minute quantities of the sub- 

 stance dissolved in methylated spirit, and in each there occurred a 

 microscopic fungal mycelium. When the sodden yang wood was 

 allowed to dry the white substance remained as a disfiguring chalk-like 

 exudation. When, in turn, a' very little methylated spirit was rubbed 

 over the surface of such dry wood, the disfigurement vanished as the 

 resin dissolved and covered the surface with a film of varnish (recalling 

 French polish in its effect). Practical trial alone can show the extent 

 to which this treatment will preserve this wood from decay, or be of 

 service in connexion with other resinous dipterocarp woods. 



In the investigations the pieces of yang wood used were in the form 

 of radially and tangentially cut boards, about 48-61 cm. in length, 

 12-13 cm. in width, and 1*35 cm. in thickness. In order to induce 

 and measure the swelling they were submerged under water and 

 measured at intervals. Thereafter they were allowed to dry at ordinary 

 temperatures in the laboratory, and measured at intervals. The first 

 measurements were made by means of a wooden rod graduated only 

 to millimetres, but subsequently use was made exclusively of vernier 

 callipers accurate to -02 mm. The changes of curvature were recorded 

 graphically by an instrument which Professor Dalby was so kind as 

 to design for the purpose. The instrument is described in a separate 

 paper, in the present issue. 



General Results. 



The most interesting results concerned the changes in length of the 

 wood during the absorption and emission of water. In both cases 

 a shortening and a lengthening took place. During the absorption 

 of water the radial and tangential boards showed successively: 



First, an increase of length together with relatively small increase 

 of width. This latter, in the one case tested, was most marked near 



