194 



GEEMANY. 



to the Rhine, is likewise a sterile country, very thinly peopled. Vast tracts of it 

 are covered with blocks of rock, which it is necessary to remove before the land 

 can be cultivated. In some parts the land is allowed to lie fallow for fifteen and 

 even twenty years, after which the grass that has sprung up in the meantime is 

 burnt, and oats are sown in the ashes. After two or three years' cultivation these 

 fields are once more abandoned. 



The Eifel is remarkable on account of its extinct volcanoes, presenting regular 

 cones, craters, streams of lava, and heaps of scoriœ. Crater lakes, locally known 

 as maare, form a distinct feature of this volcanic district. The most remarkable 



Fig. 112. — The Lake of L.\ach. 

 Scale 1 : 135,000. 



Nickenicn 





l;,-~*«Otièri Mendié '••;; 



^,\4i0 ^ ^ SI 



7 " 15' E.of Gr. 



7''20' 



amongst these lakes is that of Laach, which covers an area of 830 acres, and has a 

 depth of 200 feet. Within a radius of 5 miles of it no less than thirty-one craters 

 have been discovered, but the cup-shaped cavity now occupied by the lake appears 

 to have been produced by a gaseous explosion. Lava never flowed from it, though 

 it ejected scoriae and other volcanic products. Numerous gaseous springs rise on 

 the bottom of this lake and in its environs, and carbonic acid gas escapes in a 

 neighbouring peat moss. The surplus waters of the lake are discharged through a 

 tunnel, constructed in the twelfth century. Extensive tracts are covered with 

 pumice, not only on the left bank of the Rhine, but also on the right, as far 



