114 Notes on the Properties of Wood. 
it loses considerably of its weight, and soon after the oil 
has been put on, the wood becomes brittle and warps more 
easily than in its natural state. 
The remainder of the sap which is left in the pores of 
seasoned timber serves as a binding substance in the whole; 
it also prevents any extensive hygroscopical action, 
provided the tree was cut at the proper time. 
The hygroscopicity is in constant action in the wood, and 
affects its body, shape, and weight, which, in time, leads to 
its dissolution. This change is as much a chemical asa 
physical process, and is noticed in all woods. 
The weight of wood is of great importance to us, 
because its hardness, its resisting, and its heating power, as 
well as other valuable properties, are all, more or less, de- 
pending upon it. Let us, therefere, enter closer into this 
subject. In the first instance we must consider that even 
wood which has been forested very light, will become heavy 
when put for some time into water; but, in such timbers 
the sap is already given to dissolution. If the fibre were 
the only substance in the wood, then the specific weight 
would depend upon the number of pores contained in its 
body. The pores are, however, filled with a substance, 
such as resin, dye, &c. It comes to this, that young trees 
contain a great quantity of sap, whilst old trees have less, 
but a volume of air instead. 
Suppose we leave the troublesome factor, the water, for 
a moment, out of question, and inquire into the reasons 
which cause the heavier or lighter specific weight in dry 
wood. The hardest and heaviest woods come from the 
hotter climates. The only exception is the pine, which 
thrives considerably better and furnishes heavier timber 
when it has grown in colder regions, or upon high moun- 
tains. Trees grown on northern slopes furnish lighter 
timber than if south or west. In these remarks we have 
already noticed the fact, that the soil has great influence 
upon the width of the yearly rings, and I also remarked 
that from this we are able to form a conclusion with regard 
to the specific weight. 
We have since heard of a number of facts by which the 
connection between the yearly rings and the specific weight 
is greatly modified, but, as an instance, I mention the Fir 
and Larch trees, which both are heaviest when their rings 
are small. Another influence upon the specific weight is 
exercised by the resin and the dye which are contained in 
the interior of the wood. On level dry ground or deep 
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