General View of the Mode of Formation of Iceland. 103 



The submarine volcanic activity now first begins ; masses 

 of water are engulfed by larger or smaller rents, and, in the 

 deep, become converted into steam, which, in confined spaces; 

 exerts its immense elastic force. The wonderful display of 

 volcanic eruptions will now occur in exactly the same way 

 as is observed in our day in different seas. Through one or 

 even through several rents extending in a north-westerly 

 or north-easterly direction, but chiefly in the latter, there 

 will incessantly arise, in some favourable points, steam of an 

 elastic force of several hundred atmospheres, accompanied 

 by earthquakes, projecting into the air sea- water, together 

 with clouds of ashes and scorise, furnished by the volcanic 

 focus, and causing terror and destruction amongst the inha- 

 bitants of the ocean. 



The heavier masses, volcanic bombs and coarser scoriae, at 

 first fall back around the orifice of the eruption, and are 

 soon scattered by currents along the bottom of the sea; 

 whilst the finer pulverised ashes, drifted by the wind in dif- 

 ferent directions, first reach the surface of the sea, by a 

 longer road through the air, and cover the bottom in a thin, 

 scarcely perceptible stratum. These coming in contact with 

 the tertiary strata, whilst in the act of progressive formation, 

 there arise those tuffacious marls which I have described in 

 my account of the tertiary formation of Val di Noto in 

 Sicily, and which are more or less largely impregnated 

 with volcanic ashes. Such formations can now be found 

 only where one or several submarine eruptions have occurred ; 

 in Iceland, where they are quite covered by later eruptions, 

 they are now no longer anywhere to be seen. 



After this eruption of ashes has continued for days or 

 weeks, the lava begins to rise up in the fissures, and, as in 

 the neighbourhood of Militello, spreads by injection into the 

 lateral masses of the tertiary formations, and amongst the 

 newly-ejected ashes, or, as probably more rarel}"" occurs, 

 even flows over the latter. After these processes, which 

 have caused an instantaneous uprising, hot vapours or fuma- 

 roles make their appearance along the rent, and then the 

 eruption ceases. At last, in the course of time, the ejected 

 ashes assume their submarine character, and are changed, 

 according to circumstances, either into amygdaloidal con- 



