116 Pwa-Neyet. 
outer side. This causes the splits on the exterior after the 
wood is dry, and it also accounts for the impossibility to 
form out of greenwood a regular body which could not. 
lose its weight or shape. The time during which the eva- 
poration of the moisture takes place depends upon the 
state of the atmosphere 
Several authors are of the opinion that the contraction | 
is regulated by the specific weight. This, as a rule, cannot | 
be adopted; for instance, Lilac and Oak, both being heavy | 
and hard, contract quickly, whilst the South American : 
Maple, which is equally hard, contracts slowly. It is evi- 
dent, however, that the fuller of sap a tree is, the greater will 
be the contraction. This will account for the fact that we find 
oncut timberthe cracks extendfrom the exterior towardsthe 
centre, because the sapwood will contract more than the 
heart of the wood. Planks turn with their sides upwards, 
that is, the edges rise from the level of the centre line. 
This explains why we turn the inside of a plank towards 
the joists whilst we lay a floor, which prevents the twisting. 
The contraction and action of the wood cannot be 
checked altogether. Among the means to prevent it, stands 
foremost the one of putting the tree into water; but when 
taken out it must not be stored in a place where it dries too 
soon, as it still would burst if done. . Nor must it be left 
too long in the water as this will injure the quality of the 
wood. 
All the wood which is used is never quite dry; besides 
this, it works a little in itself, under the changes of the . 
atmosphere, and therefore attention must be paid to the | 
‘selection of timber for the same purpose, for the heartwood 
is less subjected to such actions than sap or splintwood. 
This is an important point with furniture makers. The 
extension or contraction is less apparent in the length of 
the fibre than in the cross section of the wood. 
PWAI-NGYET. 
HAVE noticed your remarks on the substance called 
Pwat-ngyet in your interesting little periodical 
“Science Gossip.” As it was I who furnished the bees 
which were forwarded by the Agri-Horticultural Society of 
