324 THE ROMAN CAMPAGNA 



lie above the travertine. In some of these may be 

 detected truly volcanic minerals such as felspar, 

 augite and black mica, derived from the explosion 

 of lava within eruptive vents and from the falling 

 of the volcanic dust upon the silt and shells of the 

 sea-bottom. Higher up more pronounced evidence of 

 successive eruptions is furnished by abundant lapilli 

 and scoriae of black slaggy lava, and by bands of 

 true tuff, composed almost or entirely of volcanic 

 detritus. 



This section at the Torretta di Quinto is of great 

 interest as indicating that the volcanoes of the Cam- 

 pagna began their career under the sea. Similar evi- 

 dence obtained at other places makes it probable that 

 the whole chain of volcanoes in central and southern 

 Italy, from those of Bolsena on the north to those of 

 Naples and Sicily on the south, started their erup- 

 tions on the sea-floor. When the activity of this 

 chain was at its height, a band of eruptive vents 

 flanked the western coast from the neighbourhood of 

 Aquapendente and Ovieto to perhaps as far as the 

 Bay of Salerno. At first the cones formed round these 

 vents were probably submerged, and were no doubt 

 more or less washed down and levelled by the agitation 

 of the sea, but as they were renewed by successive dis- 

 charges, the larger examples among them may have 

 risen above water and scattered their dust and stones 

 into the air. These volcanic islets would then front 

 the mainland of Italy, much as the Aeolian islands now 

 flank the northern coast of Sicily. Etna, Lipari, 

 Volcano, Stromboli and the other islets may be 

 regarded as the last lineal descendants of the insular 



