1850.] MURCHISON — EA.RLIER VOLCANIC ROCKS OF ITALY. 307 



worn-down side resulting from aqueous denudation, and also for such 

 sorts of scoriae, lapilli, ashes, and pumice as were ejected in the forma- 

 tion of Graham's Island. Now this is just the succession of mate- 

 rials, as far as I can judge, that occurs at Rocca Monfina, the very- 

 external folds of its volcanic system being the most scoriaceous and 

 volcanic, v/hilst the central dome of trachyte has almost the solidity 

 and compactness of a plutonic rock formed under considerable 

 pressure*. 



In endeavouring to fix the age of these volcanic operations, we 

 have unluckily no certain criteria or tests to appeal to ; for the 

 valleys of the Garigliano on the west, and of Teano on the east, 

 which flank Rocca Monfina, contain, as far as I know, no remnants 

 of deposit with marine or ancient lacustrine remains; but judging 

 from analogy, and from that continuous undulation from this tract 

 into the Phlegrsean Fields, I have little doubt that the surrounding 

 tufaceous accumulations are nearly of the same age. But whilst we 

 can attach no exact idea of age to the term " felspathic tuff" of the 

 Phlegrsean Fields, there is still a point on which we may rest, viz. 

 that in a general sense all the region between the Bay of Naples and 

 Rocca Monfina, a distance of upwards of thirty miles, and occupying 

 the valleys in the Apennine limestone, both to the east and west of 

 our volcano, is filled up with undulations of earlier volcanic rocks 

 or ancient alluvia, which most authors consider to have been as un- 

 questionably accumulated under water, as those of the Campagna 

 di Roma. Now some of the portions of these which flank three sides 

 of the excrescence of Rocca Monfina are unquestionably superior, or 

 of younger agef . 



In drawing our conclusions, it is well to remark, that we cannot 



* In a sketch of the relations of the rocks in the kingdom of Naples, M. Pierre 

 de Tchihatcheff gives the following as the ascending order in time of the volcanic 

 productions of that region : — 1. Monte Gargano and the eruptions along the 

 Adriatic line ; 2. Monte Vulture ; 3. Phlegrsean Fields ; 4. Rocca Monfina ; 5. Vesu- 

 vius ; 6. Monte Nuovo. (Coup d'oeil sur la Constitution geologique des provinces 

 meridionales de Royaume de Naples. Berlin, 1842, p. 171 et seq.) I suspect my 

 clever Russian friend would not have thus written if he had more leisurely examined 

 the country. Thus, in approximating the dejections of Rocca Monfina to those of 

 Vesuvius, and in thinking that the one was the immediate precursor of the other, 

 he seems never to have seen (at least he makes no allusion to) the great and re- 

 markable central mass of trachyte at Rocca Monfina, for he admits that trachyte is 

 the oldest of all the Neapolitan volcanic products. The credulity of M. Breislak, 

 who believed that remains of Roman buildings were found under some of the tuff 

 of Sessa, and the error of Pilla, in stating that sea-shells had been found adherent 

 to the mountain of Rocca Monfina, are now both admitted. 



t A letter just received from that able naturalist Professor Scacchi of Naples, 

 dated the 25th of January, acquaints me that in two memoirs recently published by 

 him in the Transactions of the Academy of Sciences of Naples, he has more fully de- 

 veloped his views as to the origin and formation of the tuffs of the Campania. He 

 assures me, that without any doubt these accumulations axe posterior to the dejec- 

 tions of Rocca Monfina. Although there are no positive proofs of the submarine 

 origin of Rocca Monfina, Scacchi agrees with me as to the ancient and subaqueous 

 character of the trachyte of Monte della Croce (vvhich he considers almost a por- 

 phyry), that has closed a great volcanic vent, the materials around which were 

 ejected anterior to the formation of the felspathic tuffs of the Campania. In 



