1850.] MURCHISON — EARLIER VOLCANIC ROCKS OF ITALY. 299 



nos of Auvergne, still I could nowhere see any such decisive proofs of 

 terrestrial volcanicity as the French tract affords in its most recent 

 cJieires or coulees, and their direct issue from the broken-down lips 

 of craters. I came away, indeed, under the belief, that the youngest 

 volcanic rocks of Latium were probably formed anterior to the last 

 active volcanos of Auvergne ; such, for example, as the Puy de Tar- 

 taret, which I formerly examined in company with Sir C. Lyell, and 

 which has subsequently had such decisive proofs of its modernity ad- 

 duced by my associate * . In other words, I apprehend, that in Latium 

 they formed the last part of a continuous series of active igneous opera- 

 tions, which being submarine and to a great extent subpaludine in its 

 origin, assumed gradually (whilst the land was emerging, or very shortly 

 after its emergence) those intermediary and peculiar features which 

 characterize the upper dejections of the Latian Hills. I would further 

 suggest as highly probable, that whilst the old travertines near Tivoli 

 were accumulating, the Latian eruptive forces spent their last ener- 

 gies as active volcanos. This view is also home out by the striking 

 mineral distinction between these Latian rocks and those of the Cam- 

 pagna di Roma and the Colles Ciminii north of Rome. The Latian 

 rocks not only contain several simple minerals, above enumerated, 

 but are exempt from the felspar so common in the northern tract. 

 In admitting the value of this distinction (indicated by Monsignore 

 Spada), as respects the younger or true volcanic rocks of Hannibal's 

 Camp, La Tartaruga, and Tusculum, I cannot consent to group in 

 the same category the peperinos and leucitic rocks of Albano and 

 Marino. The mere absence or presence of one or more simple mine- 

 rals cannot stand in the way of geological phsenomena and general 

 physical conditions which indicate that this region was manifestly to 

 a great extent subaqueous all around the Latian volcano vrhen the 

 latter was in activity. If, indeed, we are to appeal to mineral cha- 

 racters, even then I contend, that it is quite impossible to separate 

 the peperino of Marino from that of Albano, or the latter, when 

 coarse-grained, from the leucitic peperino forming the outward dejec- 

 tions of Rocca Monfina, which, as I shall hereafter show, were un- 

 questionably formed under water. Again, though Spada furnished 

 me with specimens of what he called stratified cinder-beds between 

 the banks of the Alban peperino, I ask any unprejudiced person to 

 compare these with other rocks ticketed b}^ the same good mineral- 

 ogist as tertiary tuffs from the Tre Fontane, and with the feathery 

 light scoria, with crystals of vitreous felspar, and the pumice from 

 near Veii and other places north of Rome, where subaqueous con- 

 ditions are admitted by him to have prevailed, and then say whether 

 the peperinos from the Ciminian or those from the Latian tract have 

 the most subaerial aspect. 



That all these eruptive operations, even the last in Latium, were 

 anterior to the desiccation and elevation of the " quaternary" accu- 

 mulations of Italian geologists, which fringe the shores of the Papal 

 States in the form of raised beaches, is indeed distinctly proved by 

 the discovery, that the bibulous travertine of that age called "Macco," 

 * See Quart. Joiirn. Geol. Soc. Lond. vol. ii. p. 75. 



