80 gas-jets; mud-volcanoes. 



— the most remarkable ones in Iceland,, — that jets of 

 sulphurous acid, sulphuretted hydrogen, sulphur 

 and steam burst forth in wild confusion from the 

 hot soil of palagonite-tuff, and spread far over the 

 steaming 'sulphur-grounds/ which are in con- 

 tinual growth from the mutual decomposition of 

 the palagonite* and of these gases. The outbursts 

 of gas and vapour on these surfaces are of the most 

 various character. The curious traveller must not 

 venture to walk here without the greatest care for 

 his footsteps, lest the treacherous ground of clay 

 and sulphur should let him sink through into the 

 hot mud. On the slopes of the mountains, where a 

 layer of a harder stone prevents the solfataras from 

 spreading farther in the same manner, they gush out 

 from clefts and crevices in the rock, in the form of 

 mighty jets of steam, roaring and hissing, or, if they 

 break forth from the openings of underground 

 caverns, their deep-mouthed bellowing is truly 

 awful. — Where, on the other hand, the spring-chan- 

 nels lead down towards the valley-bottoms, among 

 the looser tuff-rock, boiling pools of mud are found, 

 in which a disgusting bluish-black clay-slime keeps 

 rising up in large bubbles, which, as they burst, 



* Palagonite is a rock composed of silica, alumina, ses- 

 quioxide of iron, lime, magnesia, potassa, soda, and water ; 

 it is abundant in Iceland ; it cannot resist the action of the 

 weakest acids, and is even partly soluble in water. 



