Ch .XVI.] HUNGARY TRANSYLVANIA STYRIA. 



breccias, wherein fragments of trachyte are bound together by 

 pumiceous tuff or sometimes by silex. 



It is probable that these rocks were permeated by the waters 

 of hot springs, impregnated, like the Geysers, with silica ; or, in 

 some instances perhaps, by aqueous vapours, which, like those 

 of Lancerote, may have precipitated hydrate of silica *. 



By the influence of such springs or vapours the trunks and 

 branches of trees washed down during floods, and buried in 

 tuffs on the flanks of the mountains, may have become silicified. 

 It is scarcely possible, says M. Beudant, to dig into any of 

 the pumiceous deposits of these mountains without meeting 

 with opalized wood, and sometimes entire silicified trunks of 

 trees of great size and weight. 



It appears from the species of shells collected principally by 

 M. Boue, and examined by M. Deshayes, that the fossil re- 

 mains imbedded in the volcanic tuffs, and in strata alternating 

 with them in Hungary, are of the Miocene type, and no 

 identical, as was formerly supposed, with the fossils of the 

 Paris basin. 



Transylvania. The igneous rocks of the eastern part of 

 Transylvania described by M. Boue, are probably of the 

 same age. They cover a considerable area, and bear a close 

 resemblance to the Hungarian lavas, being chiefly trachytic. 

 Several large craters, containing shallow lakes like the Maars 

 of the Eifel, are met with in some regions ; and a rent in the 

 trachytic mountains of Budoshagy exhales hot sulphureous 

 vapours, which convert the trachyte into alum-stone, a change 

 which that rock has undergone at remote periods in several 

 parts of Hungary. 



Styria. Many of the volcanic groups of this country bear 

 a similar relation to the Styrian tertiary deposits, as do the 

 Hungarian rocks to the marine strata of that country. The 

 shells are found imbedded in the volcanic tuffs in such a 

 manner as to show that they lived in the sea when the volcanic 

 eruptions were in progress, as many of the Val di Noto lavas 

 * See above, vol. i, chap, xxii. 



