16 
TIM BEE 
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. 
