Ch. XXXI.] LAKE-CRATERS OF THE EIFEL. 081 



the whole surface of the soil sparkling with volcanic sand, and strewed 

 with ejected fragments of half-fused shale, which preserves its lami- 

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

 coating. 



A few miles to the south of the lakes above mentioned occurs the 

 Pulvermaar of Gillenfeld, an oval lake of very regular form, and sur- 

 rounded by an unbroken ridge of fragmentary materials consisting of 

 ejected shale and sandstone, and preserving a uniform height of about 

 150 feet above the water. The slope in the interior is at an angle of 

 about 45 degrees ; on the exterior, of 35 degrees. Volcanic substances 

 are intermixed very sparingly with the ejections, which in this place 

 entirely conceal from view the stratified rocks of the country.* 



The Me erf elder Maar is a cavity of far greater size and depth, hol- 

 lowed out of similar strata ; the sides presenting some abrupt sections 

 of inclined secondary rocks, which in other places are buried under 

 vast heaps of pulverized shale. I could discover no scoriae amongst 

 the ejected materials, but balls of olivine and other volcanic substances 

 are mentioned as having been found.f This cavity, which we must 

 suppose to have discharged an immense volume of gas, is nearly a 

 mile in diameter, and is said to be more than one hundred fathoms 

 deep. In the neighborhood is a mountain called the Mosenberg, 

 which consists of red sandstone and shale in its lower parts, but sup- 

 ports on its summit a triple volcanic cone, while a distinct current of 

 lava is seen descending the flanks of the mountain. The edge of the 

 crater of the largest cone reminded me much of the form and charac- 

 ters of that Vesuvius ; but I was much struck with the precipitous and 

 almost overhanging wall or parapet which the scorise presented 

 towards the exterior, as at a b (fig. 727) ; which I can only explain by 



Stratified rocks. v. Volcanic. 



■ Outline of the Mosenberg, Upper Eifel. 



supposing that fragments of red-hot lava, as they fell round the vent, 

 were cemented together into one compact mass, in consequence of 

 continuing to be in a half-melted state. 



If we pass from the Upper to the Lower Eifel, from a to b (see 

 Map, p. 678), we find that celebrated lake-crater of Laach, which has 

 a greater resemblance than any of those before mentioned to the Lago 



* Scrope, Edin. Journ. of Science, June, 1826, p. 145. 

 f Hibbert, Extinct Volcanoes of the Rhine, p. 24. 



