VV ■ 4i i
‘ A' ; ..;,v;G
' ‘i '.ri.V V.;-,:,,!'
: V'i : G;.G
ii
%U 7
:: I
1 ;
.■ .(V"■ «G■ ,
: G "
V B < ^
7 ^
'I: '
• ■
i ' :
.G" ' ' ' ■ , i '
I " : • i
[ 286 ]
foifalts at Bolfenna, which are like
thofe that abound in the lava of Ice-
fond ^nd Italy, .And laftly, a kind of
¿one near Laugarnas in Iceland, which
was much coarfer, and more glafty than
the cqmmon bafalts, and evidently was
fova burft into polyedrous and regular
%ures, though not quite fo regular as
the above-mentioned pillars.
What I have here faid, might eafily
induce one to imagine that the bafalt,
after having been melted, and become
cold again, had fieen burft into fuch
pillars. But two objcdipns, that
yon raife againft this opinion, are
difficult to be removed. Firft, this
matter melts fo eafily, that it becomes
glafs without difficulty, before the
blovv-pipe for aflaying, whence it feems
diat this mafs muft neceffarily have
been changed to glafs, i f it had been
expofed to fo great a fire as that
o f an eruption. But may one fafely
judge of an experiment made in miniature
by the blow-pipe o f the
workings o f nature at large ? Might
not, perhaps, an addition we are unr
acquainted with, have prevented the
mills
’ k!
),■
' ' 1
[ 287 ]
mafs from becoming glafs, and caufe
it to break, into thefe regular figures,
though we cannot now determine
wherein this addition coniifted ? Secondly,
we find that the trapp in
Weft-Gothland, which both in appearance
and fubftance fo much refenible
bafalts, though it does not form itfelf
into pillars, ftands on flate ; and how
could this trapp have been formed
by the fire, without, at the fame time,
adling on the bed, which is o f fo com-
buftible a nature ? But ihould not,
perhaps, the fire be able to form the
trapp into pillars ? Perhaps all bafalt
pillars may have been a mafs o f trapp
in the bowels of the earth, that being
liquefied during an eruption, was
thrown up, and fplit into pillars.
But, Sir, I fear to fatigue you with
my conjectures and queilions ; it
would, however, be very agreeable
to me and other naturalifts, i f you
would kindly communicate to us your
thoughts on this fubjeCl. This would,
no doubt, enable us to judge with
more certainty of the bafalts, that at
prefent
&