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AGATE. 
of decayed lava. The bitumen is strongly attached 
to the crystals of calcareous spar, and has even 
penetrated their substance, while the crystals of 
quartz are not in the least affected by it. The stones 
which exhibit this singular phgenomenon are four 
or five inches in diameter, and the quantity of pitch 
they contain sometimes amounts to several ounces. 
In Dauphiny little lenticular chalcedonies are 
frequently met with, which are called swallow stones. 
They have obtained this name from being found in 
swallows’ nests, and the country-people, willing to 
find an use for the stones, suppose the birds collect 
them to rub the eyes of their brood in order to clear 
their sight. 
Carnelian, 
Carnelian is a red variety of agate found among 
old lavas, and frequently in the neighbourhood of 
white chalcedony. The most beautiful specimens 
of this stone are brought from the banks of the 
Euphrates, near antient Babylon ; they are likewise 
found of equal value along the Persian Gulf and 
the Red Sea, from whence they are transported to 
Surat ; and it is by nearly the same route that we 
procure other stones of a similar nature, and espe- 
cially the fine arborescent agates. The carnelians of 
Europe are less esteemed, being generally of mixed 
tints. They are found in the island of Sardinia, 
on the borders of the Rhine, in Bohemia, and in 
Silesia. To be valuable they ought to be of a clear, 
lively, and equal red colour. 
