IV. dn Anatysis of the WATERS of fome Hot Sprincs in 
IceLANnD. By FosEpH BLack, M.D. Profeffor of Me- 
dicine and Chemifiry in the Univerfity of Edinburgh, Firft 
Phy/fician to his Majefty for Scotland, Fellow of the Royal 
College of Phyficians, and of the Royal Society of Edinburgh; 
Member of the Academy of Sciences and of the Society of Me- 
dicine of Paris, of the Imperial Academy of St Peterfburgh; 
&e. &e. 
[Read Fuly 4. 17916] 
IR JosepuH Banks, to whofe indefatigable ardour for thé 
advancement of natural hiftory, the philofophical world 
is fo much indebted, made a voyage to Iceland in the year 
1772, to enquire into the productions of that remote part of 
the world, and particularly into thofe of its famous volcano. 
When he returned, he brought from thence, among many other 
natural productions, fome petrified vegetables, and incrufta- 
tions, formed by the waters of the boiling fprings; and he was 
{ fo good as to prefent a part of them to his friends here, who 
were furprifed to find them compofed of filiceous earth. As 
this was the firft example obferved, of water containing this 
earth in fuch quantity as to form filiceous petrifactions, it raifed 
a ftrong defire to have an opportunity of examining the water, 
and of learning by what means this filiceous matter was dif- 
folved in it; and this opportunity was at laft given us by 
{ Joun Tuomas Sranvey, Efq; who, excited by motives fimi- 
lar to thofe of Sir Josepu Banks, equipped likewife a veflel, 
and made a voyage to Iceland, during the fummer 1789. He 
; brought 
