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Sian pole a AS 
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HOT SPRINGS in ICELAND. 133 
bright, and the veins were marked with more delicacy. The 
tranfition likewife from one fubftance into the other, was more 
evident and fatisfactory. 
To the depth of a few inches, the ground confifted of loofe 
lavas, broken and pounded together, of blue, red and yellow 
colours. The blue lava was hardeft; and feveral pieces of it 
remained firm and unaltered, while the reft were reduced to a 
duft. The colours became brighter as the decompofition of the 
fubftances advanced, and they were changed at the depth of 
nine or ten inches into a clay ; excepting, however, the pieces 
of dark blue lava, which ftill retained fufficient hardnefs to re- 
fift the preffure of the finger. Round thefe, (which appeared 
infulated in the midft of the red and yellow clay), feveral veins 
or circles were formed of various fhades and colours. A few 
inches deeper, thefe alfo became part of the clay, but ftill ap- 
pearing diftinét, by their circles, from the furrounding mafs. 
The whole of this variegated fubftance refted on a thick bed of 
dark blue clay, which had evidently been formed in the fame 
manner from fome large fragment of blue lava, or ftratum of 
it, broken into pieces. 
Tue refemblance of thefe clays to jafper is fo ftriking to the 
eye, that I cannot forbear believing their origin to be fimilar, at 
leaft, that fome circumftances in the formation of each are the 
fame. You will fay, with reafon, that the difference, notwith- 
ftanding the apparent fimilitude, is in reality very wide; that 
thefe clays, before they can be converted into jafpers, require 
to be confolidated, and impregnated with a confiderable propor- 
tion of filiceous earth. It is fomething, however, to have de- 
tected nature in the act of forming, in any fubftance, the veins 
and figures common to marbles and jafpers. What {till re- 
mains of the procefs, after thus much of it has been traced, 
may not long continue unknown ; and in Iceland, probably 
fooner than elfewhere, will be difcovered beds of clay, like this, 
hardening into ftone, either by the effect of fubterraneous heat 
or 
