16 TIMBER 



some soft material, so that the blocks may expand longi- 

 tudinally without injuring the contour or affecting the kerbs. 

 But even with this arrangement it is not at all unusual 

 for an inch or more to have to be cut off paving blocks 

 parallel to the channels some years after the paving has 

 been laid, owing to the expansion of the wood exceeding 

 the amount allowed. Considerable variation occurs in the 

 expansion of wood blocks, but it occurs in the Australian 

 hardwoods as well as in the pine timber, and is often 

 greater in the former than in the latter. Expansion takes 

 place in the direction of the length of the blocks as they 

 are laid across the street, and causes no trouble in the 

 other direction, the reason being that the lengthway of a 

 block is across the grain of the timber, and they expand or 

 contract as a plank does. On one occasion, in a roadway 

 forty feet wide, expansion occurred until it amounted to 

 four inches a side, or eight inches in all. This continual 

 expansion and contraction is doubtless the cause of a good 

 deal of wood paving in streets and buildings working loose. 



