218 Analyses of Books* [Sept. 



has done in the case of the modern volcanoa of Auvergne, that 

 although of post-diluvial origin, they were in action before the 

 existence of historical records. There is, indeed, a passage in 

 Tacitus, which has been supposed to refer to something of a 

 volcanic nature that occurred in this district; but our author 

 ridicules such an idea, and concludes that nothing more was 

 meant, than an accidental conflagration, caused, perhaps, by 

 setting fire to the woods or heaths, in a dry season. 



" It is certain at least that the lava of Niedermennig existed 

 in the time of Augustus, for the pillars of the ancient bridge of 

 Treves are formed of this material. 



*' We are, therefore, under the necessity of attributing to the 

 Eyfel volcanos a date historically very ancient, though, geologi- 

 cally speaking, modern, since geological research may be said 

 almost to terminate where history begins : if we adopt the 

 opinions of Prof. Buckland respecting the excavation of the 

 valleys, we must suppose these rocks to have been formed, like 

 some of those in Auvergne, subsequently to the Deluge recorded 

 by Moses ; or if, hmiting ourselves to those views in which all 

 geologists concur, we choose to speak more indefinitely, the 

 date of their eruptions must be pronounced to be posterior to 

 the event which reduced the surface of the globe to its present 

 condition." P. 65. 



The remaining volcanic rocks in this part of Europe, appear to 

 be of an older date, and are shown by the author to belong to 

 that period in the history of the globe, during which the rocks 

 called tertiary were being deposited. The trachytes and basalts 

 of the Seven Mountains near Bonn, of the Westerwald near 

 Cobientz, and of several other chains of mountains in the same 

 neighbourhood, belong to this class. The mode of their forma- 

 tion is illustrated, by considering certain conical masses of 

 basalt, which occur detached in Hessia, the structure and rela- 

 tions of which are sufficiently exposed, to allow of their being 

 studied with exactness. 



In the case of the Pflasterkaute near Eisenach, " the exca- 

 vations are carried to such a depth, that we are enabled distinctly 

 to see the basalt more than 50 feet below the surface of the 

 sandstone. The line of junction is also well-displayed, and we 

 observe the sandstone changed from an horizontal to a vertical 

 position, spHt in all directions, and rendered harder and whiter, 

 where the basalt touches it.'' P. 72. 



In another case, the portions of sandstone form clusters of 

 little prisms, possessing even greater regularity of form than 

 those of the basalt which encircles them. " It is curious,** 

 remarks our author, " to trace the resemblance between the 

 prisms here alluded to, and those produced artificially in several 

 parts of Derbyshire and Yorkshire, where the soft friable sand- 



