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 scoria? sparingly scat- 
tered over the surface, till at length on reaching the summit 
he finds himself suddenly on the edge of a tam, or deep 
circular lake-basin. 
No. 49. 
The Gemunden Maar. 
This, which is called the G-emunden 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 
O 2 
