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 aflumed 

 the form of a tranfparent jelly, which had nearly the thicknefs 

 of half a crown. This jelly afterwards became divided by fif- 

 fures, into a great number of fmall portions, which, in drying, 

 contracted their fize, and greatly widened the fifTures, 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 flrongly, 

 and required much patience to fcrape it off with a knife. 



These phenomena are exactly fimilar to thofe which appear 

 in evaporating water which contains filiceous earth, diffolved in 

 it artificially by means of an alkaline fait. 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. 



While thefe dry extracts were kept for fome time in the 

 glaffes, placed in a cold room, in the winter feafon, they at- 

 traded humidity, and the extract of Geyzer attraded the mofl. 

 Eight grains of the extract of Rykum attraded in one week 

 four grains of humidity ; the fame quantity of the extrad 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 firil by attracting 

 humidity. This I imputed partly to the ftate of the atmo- 

 fphere, and partly to their having attraded fixed air, by their 



N 2 union 



