lar column, in the cave* at Caftleton. This
is as hard as any bafalt I have feen; is
compad ; contains hornblende ; and fome
patches or ftreaks of red jafper. This fort
is alfo found near Buxton, containing zeolite
and calcedony. In no inftance does it
prefent veins of lead ore, or any mineral
fubftance, at leaf!; in Derbyfhire. The appearance
of this variety affumes fo many
different characters, according to its ftate of
decompofitipn, that it is very difficult to
trace its origin. The bafalts I met with
at Salifbury craggs, near Edinburgh, alfo
near Glafgow, in the ifland of Mull, and in
Staffa, when in decompofition, have every
appearance and exterior charaCteriftic of
fotne of the varieties of the Derbyfhire
amygdaloid.
It has not any appearance of ftratification.
* This is a deep ravine at the back pf the caftle; an'd
tnuft not be confounded with the cavern at Peak’s hole.
It refills acids. No vegetable nor marine
figures have o been found in it $ nor any
chara&eriftic mark to evidence that it was
formed at the fame time, or by the fame
means, as the limeftone ftratum which it
divides. The exterior, or what has been
expofed to the atmofphere, refembles a
Peoria or vitrified mafs ; but this appearance
may proceed from its containing oxyd of
iron i and it abforbs moifture. The fracture
of a dull colour; earthy fmell when
"breathed on. It certainly contains iron in
a large proportion, which is eafily attracted
by the magnet after torrefaCtion. It divides
the limeftone ftratum, interfering and cubing
off the veins of ore, as at H, which are
again found by cutting'through it to G.
It frequently fills up fiffures of great depth,
as at O, while at a fmall diftance ftom fuch
fiffures, it is only a few fathoms in thick-
pefs. '