236 REACTION OF THE INTERIOR OF THE EARTH 



globe, on continents, in the greatest depths of the ocean, 

 and in the highest strata of the atmosphere, as demon- 

 strated by Ehrenberg, constitutes one of the most 

 brilliant discoveries of our age) have in the Eifel their 

 principal seat in the rapilli, trass-beds and pumice- 

 conglomerates. Silicious-shelled organisms abound in 

 the Brohlthal and in the erupted masses of Hochsim- 

 mern ; sometimes in the trass they are mingled with un- 

 carbonised branches of Coniferae. The whole of this 

 minute organic life is, according to Ehrenberg, a fresh- 

 water formation ; it is only exceptionally, in the upper- 

 most deposit of the friable yellowish Loess, at the foot 

 and on the sides of the Siebengebirge, that marine Poly- 

 thalamia are found, indicating the brackish character of 

 an ancient coast district. ( 319 ) 



Is the existence of the phenomenon of Maars confined 

 to Western Germany ? Count Montlosier, who was well 

 acquainted with the Eifel by his own observations in 

 1819, and recognised the Mosenberg as one of the finest 

 volcanoes which he had ever seen, regards (like Rozet) 

 the Grouffre de Tazenat, the Lac Pavin, and the Lac de 

 la Grodivel, in Auvergne, as Maars, or explosion-craters. 

 They are hollowed out of very different kinds of rock, 

 granite, basalt, and domite (trachytic rock), and are sur- 

 rounded at the margin by scoriae and rapilli. ( 3 -) 



The framework or scaffolding, which the more 

 powerful eruptive activity of volcanoes may be said to 

 construct by the upheaving and uplifting of the ground, 

 and by the streams of lava poured forth, has been 

 observed under at least six different forms, and these 

 different forms are found distinctly repeated in the most 

 distant regions of the earth. To a native of a volcanic 



