222 Geological Society. 



balls, like volcanic bombs, of varieties of trachyte, quite distinct in 

 character from any found en masse. It is traversed in many places 

 by trap dykes; and as these last are also found traversing solid tra- 

 chyte, the subsequent eruption of the trap is demonstrated. He 

 discovered no instance of the recurrence of trachyte after basalt had 

 begun to flow. There is on the side of the Rhine, opposite to the 

 Siebengebirge, an extinct volcano, of comparatively modern date, 

 the Rodderberg, composed of cinders and scorified rocks. The cra- 

 ter is about a quarter of a mile in diameter, and a hundred feet 

 deep : a farm-house, surrounded by corn-fields, stands in the middle 

 of it. 



The brown coal formation is composed of beds of loose sand, 

 sandstone, and compact siliceous conglomerate, which often, in mi- 

 neral structure, cannot be distinguished from many varieties of grau- 

 wacke ; of clay, abounding with balls and layers of clay ironstone j 

 and of many varieties of lignite, from the state of a light brown earth, 

 to a black compact shining mass, or jet. All of these are frequently 

 met with in thick beds, and the lignite is most extensively worked for 

 fuel. They contain numerous impressions of leaves, and stems of 

 trees are very abundant. With the exception of casts olLymncca and 

 Planorbis, in an opake white chert, of very limited extent, no shells, 

 fresh-water or marine, nor any remains of mammalia or birds, have 

 been found in any part of the formation ; but in some beds of the 

 lignite, impressions of fresh-water fishes, the Leuciscus papyraceus of 

 Agassiz, are found in great abundance, and there have also been found 

 extinct species of frog, salamander, and triton, together with remains 

 of insects, which Professor Goldfuss considers to belong to the genera 

 Lvcanus, Cerambyx, Anthrax, Cantharis, and eight others. 



The author submitted the specimens which contain impressions of 

 leaves, to the examination of Professor Lindley. Most of them are in 

 too imperfect a state to admit of any accurate determination, but 

 they consist generally of casts of portions of dicotyledonous leaves ; 

 and among them are two species, the existence of which is suffi- 

 cient to determine the relative age of the formation, and, with great 

 probability, the then warm climate of the North of Germany, viz. 

 Cinnamomum dulce and Podocarpus macrophyllus : there are besides 

 impressions of leaves very clearly belonging to the Palm. It is re- 

 markable, however, that a recent examination by Professor Ndgge- 

 rath of Bonn, and M. Cotta of Heidelberg, of an extensive suite of the 

 woods found in this brown coal formation, did not disclose a single in- 

 stance of a monocotyledonous tree. 



A vast deposit of gravel, chiefly composed of quartz, but containing 

 also a few fragments of basalt, trachyte, transition limestone, and 

 hunter sandstein, lies over the brown coal formation, sometimes 

 being only a thin covering, at others attaining a thickness of 125 

 feet. It is very distinct in character from the gravel now forming the 

 bed of the Rhine, and is older than some of the volcanic eruptions, 

 for a patch of it rests on the edge of the crater of the Rodderberg, 

 covered by volcanic ashes. 



The author next proceeds to point out what he considers the rela- 



