AGATE. 
417 
by this means not only the artificial colour disap- 
pears, but also many of the tints which were natural 
to the stones. 
The agates of Oberstein, those of Deux-Ponts, 
and in general those of the volcanic hills which are 
found between the Rhine and the Moselle, very 
frequently exhibit collections of coloured ramifica- 
tions which naturalists have compared to mosses, to 
byssus, or to confervae, and have even gone so far as 
to describe the genus and species to which they be- 
long. Although this mode of arranging the stones 
has been very properly rejected, as the figures are 
mostly occasioned by metals, yet M. Patrin thinks, 
nevertheless, that real vegetables have been found 
enveloped in agate. u I have seen,” says this 
mineralogist, “ pieces of stone where this has ap- 
peared so evident, that they could scarcely be taken 
for any thing else. I can almost say the same thing 
of those agates which contain masses of green fila- 
ments resembling confervae.” 
The most beautiful arborescent agates come from 
Surat, in the gulf of Cambay; these, being trans- 
ported from Mocha in Arabia, have obtained the 
name of Mocha stones. 
It is not uncommon to find animal and vegetable 
substances converted into agate. Patrin tells us 
that the northern countries are rich in (what he 
calls) agatised wood, and mentions trunks of trees of 
a foot in diameter and several feet long, preserved 
in the cabinet of Vienna, which take a very fine 
polish. Entire trees converted into agate, were 
2 E 
VOE. III. 
