WATERS from ICELAND. 99 
be afcertained, both before the water is put into it, and after 
the extract is taken out. 
In the end of thefe evaporations of the Iceland waters, they 
emitted an odour fimilar to that of alkaline leys, which contain 
an alkali not very pure or well calcined, and afterwards, when 
the evaporation was nearly completed, the refiduum affumed 
the form of a tranfparent jelly, which had nearly the thicknefs 
of half a crown. This jelly afterwards became divided by fi 
fures, into a great number of {mall portions, which, in drying, 
contracted their fize, and greatly widened the fiffures, forming 
at laft a number of fmall fragments of white cruft, unconnect- 
ed with one another, and not adhering to the bottom of the 
glafs. A fmall quantity only of this matter attached itfelf to 
the fides of the glafs during the evaporation, and formed there 
circles of an exceeding thin incruftation, which adhered ftrongly, 
' and required much patience to {crape it off with a knife. 
Tuese phenomena are exactly fimilar to thofe which appear 
in evaporating water which contains filiceous earth, diffolved in 
it artificially by means of an alkaline falt. The colour of the 
dry matter obtained from Rykum water, was almoft a pure 
white, that of the water of Geyzer was a yellowifh white. 
Wuite thefe dry extracts were kept for fome time in the 
glafles, placed in a cold room, in the winter feafon, they at- 
tracted humidity, and the extract of Geyzer attraGted the moft. 
Eight grains of the extra@ of Rykum attra@ted in one week 
four grains of humidity ; the fame quantity of the extra@ of 
Geyzer attracted in the fame time ten grains of humidity. My 
attention, however, was turned for fome time from thefe expe- 
riments ; but refuming them again after fome months, I found 
_ that thefe extracts remaining in the fame glaffes, and in the 
fame room, had again become dry, and had loft the greater part 
of the weight which they had acquired at firit by attracting 
humidity. This I imputed partly to the ftate of the atmo- 
fphere, and partly to their having attraCed fixed air, by their 
N 2 union 
