PINUS SYLVESTRIS. 
19 
or colophony ; this latter was originally the name of a liquid resin 
brought from Colophon in Greece, and is mentioned by Galen and 
Dioscorides ;* this substance is familiar to all our readers as fiddler's 
rosin. If while the mass of turpentine used in the distillation be still 
fluid a quantity of water be added and thoroughly blended with 
the resin by agitation, the under part of the cake resembles colo- 
phony, the action of the fire having entirely expelled the water and 
volatile oil and rendered it slightly empyreumatic and transjiarent, 
while the upper part from retaining some water is opaque and 
yellow, this is called yellow resin. I'lie medical properties of these 
two substances are essentially the same, and their composition will 
be readily understood from what we have already said. 
Medical Properties and Uses. These resins are never 
used internally, but from their adhesive qualities they are an 
indispensable ingredient in the composition of many plasters, while 
the resin itself, as a calefacient, aids the effects of many of them. 
Colophony is likewise much used in the arts, entering in the com- 
position of several varnishes, being dissolved in alcohol, in which it 
is perfectly soluble. 
Resina Empyreumatica Pin I vel Pix Liquida. 
Tar is a well known substance in commerce ; it is obtained from 
the Pinus Sylvestris and all the other species which yield turpentine, 
by the following process. A conical hole is dug in the earth, com- 
municating at the bottom with a reservoir; billets of the wood are then 
placed, so as not only to fill the cavity, but to form a conical pile 
over it,f which is covered with turf, to prevent the flames from 
breaking out, by which the tar would be consumed. The pile being 
kindled at the top, the admission of air is so regulated, that it burns 
from above downwards, with a slow and smothered combustion. 
The wood itself is reduced to charcoal, and the smoke and vapours 
formed are obliged to descend into the excavation in the ground. 
* It also entered into the composition of the discutieht plaster of Celsus, and is 
reeominended by Scribonias as a purgative. 
t We are informed by Theophrastus (lib. ix, cap. 3) who gives a circumstantial 
account of the manner practised by the Greeks for obtaining tar, (ntrra, Tlia-a-a vy^itt^ 
Kiwvof.) that these piles were sometimes one hundred and eighty cubits in circuiU'^ 
ference, and from sixty to one hundred in height. 
