Mineralogy and Geology of Nova Scotia. 229 
which have been detached from the precipices above, and pro- 
fusely scattered along their base at the water’s edge, we found 
in abundance agates of various kinds, and possessing great beauty. 
Some were of the variety called fortification agate, from a resem- 
blance to military works, on the polished surface of the specimens. 
This variety is often found well characterized on the shore; 
sometimes in small nodules, which have been polished by attri- 
tion, and resemble the Scotch pebble in every respect: at other 
times it is found in large tabular masses, which are evidently the 
ruins of veins from the overhanging trap rocks. The specimens 
of this vicinity frequently contain the outlines of many fortifica- 
tions in the compass of a few inches. The base of this agate is 
an opaque white chalcedony, alternating with rows of trans- 
parent quartz and yellow .jasper, the last generally constituting 
the external layer. Fine brecciated agates were also met with, 
composed of angular masses of red and yellow jasper cemented 
by transparent and amethystine quartz, often enclosing, in geodes, 
beautiful crystals of purple amethyst, which, covering the whole 
interior of the cavity with protruding crystals, vie in beauty with 
any specimens brought from the banks of the Rhine. A large 
geode was found on the shore of St. Mary’s Bay, which, weighing 
more than forty pounds, was composed almost entirely of the 
richest purple amethyst, the mass having but a thin coat of forti- 
fication agate externally. On an examination of the crystals of this 
geode, we found a substance of a reddish brown color, traversing 
the amethyst, in fibres or acicular crystals, which, beginning at the 
implanted extremity of the crystal, shoot out into diverging, sco- 
piform, and fasciculated groups, to the opposite extremity. On 
exposure to a full red heat, this amethyst losesits color, becomes 
transparent, and has a vitreous lustre ; the included fibres, at the 
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