ON ITS EXTERIOR. VOLCANOES. 229 



land, Murchison, and Thurmann, in the sedimentary 

 rocks of the North of Germany, in Herefordshire, and 

 in the Jura Mountains of Porrentruy, are connected 

 with the phenomena which have been here described ; 

 as are also, though with a less measure of analogy, some 

 high plains in the Cordilleras, closed in on all sides by 

 mountains, on which are situated the towns of Caxa- 

 marca (at 9362 feet above the sea), Bogota (8728 feet), 

 and 'Mexico (7469 feet); and in the Himalaya the 

 valley of Cashmere, 5820 feet above the sea. 



Less nearly related to the " craters of elevation " than 

 the above described simplest form of volcanic activity, 

 are the numerous caldron-like depressions, surrounded 

 by but little raised margins which they have them- 

 selves formed, which are found among the extinct 

 volcanoes of the Eifel, in non-volcanic rock, Devonian 

 schist, and which are called "Maars." "They are as 

 it were mine-funnels, evidences of mine-like explo- 

 sions," recalling the singular phenomenon described 

 by myself at the earthquake of Riobamba (4th of 

 February 1777), when the bones of men were cast forth 

 on the hill of La Culca. ( 314 ) Where, in particular 

 cases, such ancient explosion-craters situated at no great 

 elevation, in the Eifel, in Auvergne, or in Java, are 

 filled with water, they may bear the name of Lake- 

 craters, which has been given to them ; but that term 

 ought not to be regarded as synonymous with the 

 German "Maar," inasmuch as on the summits of the 

 highest volcanoes, on true cones of elevation, in extinct 

 craters, (for example, on the Mexican volcano of Toluca 

 at 12,245 feet, and on Mount Elbourz in the Caucasus 

 at 19,716 feet,) small lakes were found by myself and 



