122 4n ANALYSIS of 
at the foot of thefe, and in which the fprings rife, is compofed 
of fragments of thefe lavas; but in digging into this foil or 
rubbifh to a {mall depth only, thefe fragments are every where 
found refolving, or refolved, into a matter like clay. At a cer- 
tain depth, the fragments of fome fpecies of lava remain entire 
and hard, while the reft are changed. At a greater depth, even 
_ thefe more durable kinds are found to have undergone the fame 
change with the reft. As this change is produced by the con- 
ftant aétion of the hot water, it probably depends ona gradual 
diffolution and extraction from thefe lavas of fome of their in- 
gredients, which are diffolvable in water ; and thofe which we 
have actually found in the water may have been fome of thefes. 
But I offer all this as a conjecture only, which every perfon who. 
does not like it is at hberty to reject. 
I sHALL venture further to offer another conjecture, which. 
fome particulars I learned by Mr STANLEY’s voyage to Iceland: 
have fuggefted to my mind. It is concerning the origin of the: 
pure fulphur, which is found at the furface of the earth, in the: 
neighbourhood of many volcanos in different parts of the: 
world. In Iceland, there are places in which fulphur is thus 
found in very great quantity, covering the furface of the 
ground, and that of the ftones and rocks, in form of a thick: 
cruft, and conftituting what are called fulphur banks. This. 
was feen in Iceland in particular fpots, in which there were very 
{trong fulphureous hot fprings, which emitted fuch a quantity 
of fulphureous or hepatic gas, that the air all around was in- 
feéted with it to the higheft degree, and the water itfelf was 
muddy and black, and conftantly boiling. Now, as we know,. 
that vital air has the ‘:power to decompound this gas, and to. 
make it depofit the fulphur which it contains, I am of opinion, 
that the fulphur which appeared in fuch quantity in the vicinity 
of thefe fprings, had been depofited and accumulated in this 
manner from the hepatic gas, which thefe ftrongly fulphureous 
fprings have emitted during a great length of time. 
A Ps 
