! > il
i
ters; and it is belived, with great probability,
that the latter proceeds from
the fea, as a quantity o f fait fufficient
to load feveral horfes has frequently
been found after the mountain has
difcontinued boniing,
Tben follows generally brown or
black pumice-ftone, and lava, with
fand and affies.
The Java is ieldom found near the
opening, but rather tuff or loofe allies
and g r i t ; and indeed the greater part
pf the Icelaqdic mountains confifts of
Riis matter, which, \vhen it is grown
cold, generally takes aq arched form,
fome admirable proof o f this may be
feen in the cleft at Allmnnegiaa : the
upper cruft frequently grows cold and
folid, whilft tlie melted matter beneath
jt continues liquid; this forms great
cavities, whofe walls, bed, aqd roof
are of lava, and where great quantities
o f ftaladlites o f lava are found.
There are a great number of thefe
caves in Iceland, fome of which are
very large, and are made ufe o f by the
inhabitants for fiieltering their cattle.
I wi l l
J will here only take notice o f the cave
of Surthellir, as the largeft of all : it is
between 34 and 36 feet in height; its
breadth is from 50 to 54 feet, and it
is 5034 feet long.
It would be both tedious and difficult
to clafs the different compofitions
of fire in thefe places, as it is not
eafily difcovefed to which they belong:
for example, jafper, o f which great
quantities o f red and black are found
inclofed i|i the lava, and mixed with
i t ; I will therefore only name thoie
that have been evidently produced by
the fire, Firft, tuff, a ftone offerrumi-
iiated aflies and grit, which fometimes
is found mixed with lava, bafalt, and
other forts o f ftones, and having been
moiftened by the fpouting o f water,
grows hard by heat and length o f time.
Secondly, lava, is that kind o f ftone
that has been melted by the violence
of the fire, and varies according to
the difference o f the ftate in which it
ferved as food to the fire. This lava is
fometimes found folid, and at other times
porous and full o f bladders and holes ;
■ in
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