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M' "77 II 7
L E T T E R X X V .
From ProfeiTor B e r g m a n to Dr.
T r o i l .
O f the EffeBs o f Fire, both at the
Volcanos and the hot Springs ; and
alfo o f the Bafalts,
Stockholm, June 12, 1776.
S I R,
YOU have been fo kind as to communicate
to me your obfervations
on Staffa and Iceland, and to deiire
my opinion o f their natural curioil-
tics. It would be very ungrateful
i f I heiitated to comply with this requeil,
as you prefented me with the intire
collections you made there, that I
might chemically examine the nature
o f each. Mere obiervations, without
the ailiilance o f an exaCt knowledge
o f the fubftances, in reiped
to their original matter and compoiition,
inilead o f affording any fuf-
ficient lights whereby to enable us
to
to determine with certainty o f them,
would only lead us to draw very erroneous
concluiions. Though the form,
grain, colour, hardneis, pofition, and
external appearaiices may alliil us
in our conjedures o f the true nature
o f minerals, and ibmetimes o f
the manner in which they are produced,
yet we muil neverthelefs remain
in uncertainty till proper experiments
guide us to a more clear de-
cifion,
Forgive me for mentioning the concluiions,
which, in my opinion, might
be drawn from your obfervations, regarding
the internal nature o f thefe
fubftances, fo far as 1 have been
able to difcover them from adual
experiments. But you muft by no
means exped a fokuion o f all the difficulties
that arife on this intricate
buiinefs. I will cautioufly endea-
votir to fepa rate what is certain, fronj
what has been Jiitkerto confidered precarious
and doubtful ; a due regard
to truth will always prevent me from
offering mere conjedures, or even credible
opinions, with a peremptory de-
Y s ciiion.
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