1826.) Dr. Bauheny on Vokanos, fflf 



stone of the country, is rendered serviceable for road-making by- 

 exposure to heat, which hardens and causes it to split into small 

 columnar concretions." P. 73. 



, The hill called Blaue Kuppe, near Eschwege, illustrates these 

 phaenomena in a still more striking manner, and it is certainly 

 surprising, that with such phsenomena almost in their neighbour- 

 hood, the geologists of the Freiburg school should so long have 

 remained unconvinced of the igneous origin of basalt. 



We have no room for the sketch of the trap formations in 

 other parts of Germany, with which the first lecture concludes ; 

 neither can we notice the abstract, given at the commencement 

 of the second, of Beudant's researches in Hungary. The author 

 agrees with that geologist in opposition to Humboldt, in attri- 

 buting a different origin to the trachyte of Hungary, and to the 

 older porphyry which supports it ; but he combats the theory 

 advanced by the French naturalist, with respect to the formation 

 of the alum diffused through the substance of many beds in this 

 formation. This M. Beudant regards as the result of sulphu- 

 reous exhalations ; Prof. Daubeny as arising from the decom- 

 position of metallic sulphurets. 



Our author takes pains to show, that every one of the volcanic 

 districts already noticed, are, at the least, as modern as the 

 tertiary class of deposits ; such is likewise the case with the 

 little trachytic formation which he visited in Styria, and with 

 the greater part of the volcanic products that occur in Italy. 

 Those of the Vicentin, and of the neighbourhood of Rome are, 

 treated of at some length ; and in the Neapolitan territory a volcano 

 is . introduced to our notice, scarcely. known, we believe, to 

 English geologists, that, namely, of Mount Vultur. 



The neighbourhood of Naples is of course more particularly 

 dwelt upon, and its volcanos are treated, first, historically ; and, 

 secondly, with reference to their geological and chemical phe- 

 nomena. Under the first of these heads, must be placed the 

 question, as to whether Vesuvius was burning at any period of 

 Roman history antecedent to the Christian era ; and with the 

 view of deciding this point, our author has brought together 

 many passages from classical writers, in which mention is made 

 of the mountain. Of these, the one most illustrative of its 

 actual structure, at that period, is the account given of the occu- 

 pation of these heights by the gladiators under Spartacus, and 

 of the manner of their escape from this position. We may 

 remark, that Dr. Daubeny differs from former geologists, with 

 respect to the formation of the dykes of Monte Somma, and 

 seems loth to admit, that we have any decided case, in which 

 dykes have been formed within the crater of any volcano, or 

 since the commencement of the present order of things. 



When speaking of the Solfatara, he takes occasion to discuss 

 the origin of those sahne products, found within the craters of 



