Ch. XIV.] 



LAKE-CRATERS OF THE EIFEL. 



195 



England and Scotland, where they constitute the inferior 

 member of the carboniferous series. In the Eifel they occupy 

 the same geological position, and in some parts alternate with a 

 limestone, containing trilobites and other fossils of our moun- 

 tain and transition limestones. The strata are inclined at all 

 angles from the horizontal to the vertical, and must have 

 undergone reiterated convulsions before the country was 

 moulded into its present form. 



Lake-Craters. The volcanos have broken out sometimes at 

 the bottom of deep valleys, sometimes on the summit of hills, 

 and frequently on intervening platforms. The traveller often 

 falls upon them unexpectedly in a district otherwise extremely 

 barren of geological interest. Thus, for example, he might 

 arrive at the village of Gemunden, immediately south of Daun, 

 without suspecting that he was in the immediate vicinity of 

 some of the most remarkable vents of eruption. Leaving a 

 stream which flows at the bottom of a deep valley in a sand- 

 stone country, he climbs the steep acclivity of a hill where he 

 observes the edges of strata of sandstone and shale dipping 

 inwards towards the mountain. When he has ascended to a 

 considerable height he sees fragments of scoriae sparingly scat- 

 tered over the surface, till at length on reaching the summit 

 he finds himself suddenly on the edge of a tarn, or deep 



circular lake-basin. 



No. 49. 



The Gemunden Maar, 



This, which is called the Gemunden Maar, is the first of three 

 lakes which are in immediate contact, the same ridge forming the 

 barrier of two neighbouring cavities (see diag. No. 50). On 



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