542 



LAKE CEATEES OF THE EIFEL. 



[Ch. XXXI. 



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

 for those beds of lava and scoriae, dipping in opposite directions on 

 every side, which we have been accustomed to consider as characteristic 

 of volcanic vents. As we proceed, however, to the opposite side of the lake, 

 and afterwards visit the craters c and d (fig. 674), we find a considerable 

 quantity of scoriae 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. 



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 side slope in the interior is at an angle 

 of about forty-five degrees ; on the exterior, of thirty-five degrees. 

 Volcanic substances are intermixed veiy sparingly with the ejections, 

 which in this place entirely conceal from view the stratified rocks of the 

 country.* 



The Meerfelder 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 supports 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 of the form and characters of that of Vesuvius ; 

 but I was much struck with the precipitous and almost overhanging 

 wall or parapet which the scoriae presented towards the exterior, as at a b 

 (fig. 6*75), which I can only explain by supposing that fragments of red-hot 



Fig. 675. 



w777?7/7//7 



Stratified rocks. «. Volcanic. 



Outline of the Mosenberg, Upper Eifel. 



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

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



