58 Prof. Bischof on the Natural History of 



During the violent eruption in the low country of Skaptar 

 J ok id in Iceland^ in 1733, which suddenly brought up the most 

 enormous masses to the surface, the lava burst forth at three 

 different points, more than two geographical miles distant from 

 one another, and spread over a surface in the plain,* which is 

 supposed to equal in extent sixty geographical square miles. 

 This mass is so considerable as to surpass in magnitude that of 

 Mont Blanch Under almost the whole of Iceland there is a 

 volcanic furnace, which communicates by many apertures with 

 the surface. The masses of melted matter, therefore, seek an 

 outlet at various points, and many places are mentioned, at 

 which the lava has only been ejected once within historical 

 times. The volcanic phenomena are not confined to the island 

 alone,, they also break through in the neighbouring sea. In 

 January 1783, such an eruption took place in the sea, eight 

 geographical miles from Cape Re'ikianes, several islands were 

 raised, and great quantities of pumice and light slags were 

 floated on the coast. In June the whole island was shaken by 

 earthquakes. The submarine eruption discontinued, and at a 

 distance of fifty geographical miles the grand eruption of 



deed, very diiFerent, according to the hypothesis which Ave are endeavour- 

 ing to defend. In this the seat of the volcanic actions is supposed to be 

 identical with the place where the elastic forces producing them act. The 

 connection between the lavas, and the slags, rapilli, and ashes resulting 

 frouL them, and the rocks at the surface, would only then shew that the 

 same material which composed the rocks, raised at a former period, and 

 now spread over the surface, has also sers-ed for the production of the- more 

 recent volcanic formations. But it still remains to be taken into considera- 

 tion, that aqueous vapour, generated in the lowest point of the volcanic 

 focus, possessing its maximum of elasticity, and heated to the melting point 

 of lava, or above it, is capable, as we have already said, without the assist- 

 ance of any other power, of converting fusible roeks into a state of hydro- 

 igneous fusion. 



* See Om Tordbranden paa Island i Aaret 17^3, ved Student Soemimd 

 Mugnussen. Kort beskrivelse over den eye Vulkans, Ildsprudning i Yester 

 Skiiptcfells Syssel paa Island i Aaret 1783 of INIagnus Stephen sen. Kioben- 

 Ijavn 1785. Sir G. Makenzie's Travels in Iceland. Ganlieb's Island, 1810, 

 p. 64. Th. Gliemann geogr. Beschi'eibung von Island, 1824, p. 107. Pen- 

 nant le Nord de Globe, t. i. 



t Berghaus Abnanac for 1838, p. 75. 



