122 An A NA LrS IS 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 fmall 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 action of the hot water, it probably depends on a 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 thefe. 

 But I offer all this as a conjecture only, which every perfon who 

 does not like it is at liberty 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 

 ftrong fulphureous hot fprings, which emitted fuch a quantity 

 of fulphureous or hepatic gas, that the air all around was in- 

 fected 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. 



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