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b f the Hot Sprmgs*
OUR defcription of the Icelandic
iprings, the moil extraordinary
which have hitherto been difcovered
in the known world, was extremely
agreeable to me, partly on account
o f the furprizing force o f them, and
partly on account o f the great light
obtained in mineralogy by the cruf-
tated ilones formed in them. How
thefe fprings may be accounted for, I
hope I have fufficiently explained iii
another place ^ ; 1 iliall, thereforCj entirely
pafs it over here. But now I
will commnnicate to you what I could
not then nnderiland, namely, the true
nature of thefe depoiitions.
You have prefented me with the following
fubftances from the Geyfer :
I. The fubftance o f which the water
has prepared itfelf a bafon to run
from.— It coniifts o f a hard, rough,
greyiili, and irregular ilaty, and generally
martial cruftated ftone, over
which a covering o f fmall cryftalU-
* la my Phyfika bellcrifning om Jordlotet, ult. edit.
zations
zations has formed itfelf, that refem-
bles the lichen fruticulofus, or rather
the Stahlftein drufe found in the Wef-
terfilverberg ; that is commonly called
the Flos ferri, or Eifen bluthe. Thefe
precipitations are opaque without, o f
a whitifli grey, blacker within, and
plainly iliew the formation o f feveral
crufts on one another. Thefe, as well
as the cruftated ftone, have the hardnefs
o f a f lin t ; however they are not
fo compact or ftrong as to ftrike fire
with the fteel.
The ftrongeft acids, the fluor acid
not excepted, are not fufficient with
a boiling heat to diflblve this fubftance.
It dilfolves very little, i f at all, by the
blow-pipe with the fufible alcali, a little
more with borax, and makes a ftrong
effervefcence with fal fodas. Thefe
effeils are peculiar only to a filiceous
earth, and therefore there remains no
doubt concerning, the real nature o f
this cruftatedftone. Neverthelefs I have
melted it in the crucible ; firft, by
weight, with half as much alcaliiie ialt,
and likewife with three times as much;
Y 4 and
F