



OF EIFEL. 



143 



Upper 

 Galleky 



approaching the site of any igneous outburst. For this we 

 have been prepared by the occurrence of scoriae scattered 

 over the surface of the soil. But on examining the walls of " VYall " case 1 • 

 the crater we find precipices of sandstone and shale which 

 exhibit no signs of the action of heat ; and we look in vain 

 for those beds of lava and scoria^ dipping in opposite direc- 

 tions on every side, which we have been accustomed to 

 consider as characteristic of volcanic vents. As we pro 

 ceed, however, we find a considerable quantity of scorige 

 and some lava, and see the whole surface of the soil 

 sparkling with volcanic sand, and strewed with ejected 

 fragments of half-fused shale, which preserves its laminated 



texture in the interior, while it has a vitrified or scoriform 

 coating. 



" The most striking peculiarity of a great many of the 

 craters, is the absence of any signs of alteration or torrefac- 

 tion in their walls, where these are composed of regular 



strata of ancient sandstone and shale. 



There is, 



indeed, no feature in the Eifel volcanos more worthy of 

 note than the proofs they afford of very copious aeriform 

 discharges, unaccompanied by the pouring out of melted 

 matter, except, here and there, in very insignificant volume. 

 I know of no other extinct volcanos where gaseous explo- 

 sions of such magnitude have been attended by the emission 

 of so small a quantity of lava. : 



"In the Lower Eifel, eruptions of trachytic lava preceded 

 the emission of currents of basalt, and immense quantities of 

 pumice were thrown out wherever trachyte issued. The 

 tufaceous alluvium called trass, which has covered large 

 areas in this region and choked up some valleys now par- 

 tially re-excavated, is unstratified. Its base consists almost 

 entirely of pumice in which are included fragments of basalt 

 and other lavas, pieces of burnt shale, slate and sandstone, 

 and numerous trunks and branches of trees." — (Lyells 

 " Manual of Elementary Geology," 5th edition, pp. 54£ 



122 — Vesicular lava, Gebirge, on the Rhine. 



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