SUESS ITALIAN GEOLGGY. 9 



the Devonian of the Southern Alps. Thus between Taormina and 

 Sybaris there exists a great portion of an Alpine central chain, the 

 Apennines being its north-eastern and Sicily a part of its south-west- 

 ern subsidiary zone ; and the older rocks of the " Catena metallifera" 

 are to be regarded as the real tectonic continuation of this southern 

 central chain. 



From Palermo to Messina, and from Messina to Cape Spartivento, 

 and to the island of Capri, the Tyrrhenian sea is surrounded by 

 lines of fracture ; and even beyond this part, the promontory of Circe 

 to Elba and Spezzia, the mountain-range is immersed and broken up. 

 Beneath the Tyrrhenian sea lies the tectonic axis of the Italian 

 peninsula, which in its present state represents only the ruins of the 

 great old Tyrrhenian mountain-range projecting from the sea and 

 its younger deposits. The extra- and intra- Alpine depressions in the 

 Vienna Basin are represented in Italy by an intra-Tyrrhenian 

 (Tuscan) and extra-Tyrrhenian (Bononian) depression. 



The localities of active volcanic eruption in Italy are for the most 

 part situated along the lines of fracture, such as, especially, the great 

 zone running from Tuscany over the Alban mountains to the Phle- 

 grsean fields and Vesuvius, whilst more crowded groups of volcanoes 

 are placed more towards the centre of the area of depression (the 

 Ponza and Lipari islands). Beyond this region we have only isolated 

 volcanoes, such as, especially. Mount Etna and Mount Vultur, both 

 rising out of the Macigno. 



The impression produced on the author's mind by his recent 

 journeys in Italy is that of a loiv degree of stability of the mountain- 

 chains. At the same time the repetition of phenomena is striking, 

 e.g. the concordance of structure between the Apennines and Car- 

 pathians. In the latter the northern secondary zone is almost 

 alone visible ; the ruins of the median zone are formed by the 

 Tatra &c. ; and only traces of the southern subsidiary zone appear. 

 In the areas of depression the Hungarian trachytes make their 

 appearance in place of the volcanoes of Latium and Naples. In 

 both cases it is only a repetition, on a large scale, of the same 

 phenomenon which is presented by the intra-Alpine depression of 

 Vienna, with the thermal springs in its margins. 



Some years ago Prof. Studer indicated that the western portion of 

 the Southern Alps gradually disappears beneath the plain of Upper 

 Italy. The investigations of Gastaldi and others fully confirm this ; 

 and thus the environs of the Gulf of Genoa show how two great 

 mountain-ranges unite, and at the same time the central masses of 

 both mountains sink down, with the exception of a few fragments, 

 beneath the sea or the plain. It might even be afiirmed with 

 some probability that the sunken Tyrrhenian axis is to be regarded 

 as the true tectonic continuation of the curved axis of the Alps 

 themselves. The Tithonic fragments and the Cretaceous deposits of 

 the Euganean mountains, moreover, show that between Vicenza and 

 the Apennines the higher stages, at least, of the Mesozoic deposits 

 are connected. 



"When an abstract of the views expressed in this paper was com- 



