228 
FIR TREE. 
the trough into barrels, where it becomes a hard, 
brown, and shining substance, known by the name 
of colophony or rosin , and used for many purposes. 
When the resinous juice of the pine, thickened 
by boiling in the manner we have just described, is 
poured into a vessel containing a certain portion of 
cold water, and stirred briskly before it congeals, 
the substance changes from a brown to a fine yellow 
colour, and, in this state, is called yellow resin. 
Tar is chiefly obtained from old pines by burn- 
ing them in a close smothering heat. Great quan- 
tities of this unctuous substance are prepared in the 
different countries where fir trees abound, particu- 
larly in Norway, Sweden, Russia, Germany, and 
North America. For the purpose of extracting this 
useful material, a furnace is constructed in the form 
of an egg, and capable of holding a considerable 
quantity of wood. The furnace is not always built 
of the same size ; but is generally adapted to the 
quantity of wood intended to be burnt at a time. 
In Le Vallais, where abundance of tar is prepared, 
the largest furnace that the country-people erect 
is about ten feet high, and five or six in diameter 
near the middle. The cavity is filled with billets 
of wood cut of a proper length, and placed in rows 
one upon the other. The upper layer is covered 
with turf, well pressed down, leaving only one 
place open for the purpose of introducing the fire 
to kindle the wood. When the billets are com- 
pletely a-light, the tar begins to ooze from them, 
