282 Professor Hausmann on the Geology of the Apennines. 



plastic and slaty clay ; sandstone ; conglomerate ; and sand. 

 The latter is always the newest. In these formations fossil 

 organic remains occur, with bones of colossal animals, and 

 shells. Bitumen, sulphur, pyrites, barytes, and strontian 

 are also met with. The sulphur is often beautifully cry- 

 stallized. 



The more local tertiary formation consists of gypsum, cal- 

 careous tuffa, and volcanic tufFa. The alabaster which is 

 wrought at Florence into various ornamental articles, be- 

 longs to the gypsum of this formation. The greater part of 

 the Apennines being composed of limestone, it is easy to ex- 

 plain the production of the calcareous tufFa, at their base and 

 in the valleys. The celebrated Travertina marble is a tufFa of 

 this kind. The quantity of calcareous tufFa in Italy, and its 

 varied appearance, are wonderfully great. Prof. H. points 

 out some of the most remarkable localities. He remarks that 

 different local formations of this substance can be distinguished ; 

 some having been formed at the bottom of the sea, as is proved 

 by the marine remains found in them; while others have re- 

 sulted from the sediment of fresh-water rivers and lakes. The 

 fresh-water strata exhibit also proofs of difference in age. 

 Those which alternate with the volcanic tufFa, as seen in some 

 of the hills of Rome, the Aventine for example, and in the 

 vicinity of the city, are most ancient. Those strata which 

 cover the volcanic tufFa, and the tufFa upon which Tivoli is 

 built, are of more recent origin. The newest formation is that 

 daily forming, as at the baths of St. Philip, &c. 



The volcanic tuffa, although composed of volcanic matter, 

 in the state in which it is now observed is to be referred to 

 the aqueous depositions, as has been proved by Von Buch 

 in his excellent remarks upon the country about Rome*. 

 It appears to be confined to the south-western side of the 

 Apennines, and is separated into two portions, one of which 

 extends from the neighbourhood of Rome to the Pontine 

 marshes and vicinity of Bolsenna. The other portion, which 

 is less extensive, occurs about Naples. In the first, leucites 

 occur, but are altogether wanting in the second, into the com- 

 position of which felspar enters. 



The volcanic tufFa is of later formation than the marls, 

 sandstones, and sand before noticed ; as is well seen in the 

 neighbourhood of the Vatican, where the sand is full of marine 

 shells and rises from under the tufFa. This fact was first de- 

 scribed by Von Buch. 



Professor Hausmann concludes his memoir by remarking, 

 1st, that there are no true volcanic rocks, nor rocks of the 

 * Geognost. Beob. II. p. 60, 202. 



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