3,3 



Article II. 



On the Processes which have taken place during the formation of 

 the Volcanic Rocks of Iceland, By R. Bunsen. 



[From Poggendortf's Annalen, 1851. No. 6.] 



1 HE following memoir contains a short review of the principal 

 results which have been obtained during the course of a more 

 comprehensive investigation of the volcanic phaenomena of Ice- 

 land. A complete treatment of the subject must not be expected 

 in this place, more especially as results, which, like those here de- 

 scribed, can only be arrived at by means of an extended experi- 

 mental inquiry, require a kind of demonstration which to be in- 

 telligible cannot be given in few words. Neither do the limits 

 of the present memoir admit of my entering into a detailed con- 

 sideration of the inferences which might be deduced from these 

 investigations with regard to the general question of the forma- 

 tion of plutonic rocks. 



I have been induced to anticipate the publication of my entire 

 researches by that of this abstract, from the wish to draw the 

 attention of chemists and geologists to a series of very simple 

 relations which it will undoubtedly be possible to trace through- 

 out the whole class of eruptive rocks, and which may perhaps 

 furnish a not unacceptable groundwork for further research in 

 this direction. 



I. Genetic Relations existing between non-metamorphic Rocks, 



The rocks formed from volcanic masses ejected in a state of 

 igneous fusion consist of a mixture of silicates, which during 

 their eruption formed a homogeneous liquid. It was not until 

 after solidification that these masses assumed the form of plu- 

 tonic rocks, in which the perfect homogeneity of the original 

 mass is rarely met with. It is w ell known that the act of solidi- 

 fication is accompanied by a separation of distinctly different 

 minerals, which are either imbedded in a uniform matrix, the 



SCIEN. UEM.^Nat. Phil. Vol. I. Part I. D 



