314 PROF. G. DE LORENZO ON THE HISTORY OF [Allg. I904, 



IV. Conclusions. 



AYe have seen that, in the Bay of Naples, towards the end of the 

 Pliocene and the beginning of the Pleistocene Period, while the 

 Apennine chain was in process of uplift, eruptive phenomena which 

 were then happening beneath the waves of the sea, over an area 

 of local dislocation, laid the foundation of the volcanic districts 

 that now encircle the city of Naples. 



In that part of the region which is known as the Phlegrsean 

 Fields, we now behold a continuous succession of volcanic forma- 

 tions, the lowermost of which bear unmistakable signs of a 

 submarine origin, while the upper deposits are just as undoubtedly 

 of subaerial origin. The earlier deposits bear witness to phe- 

 nomena of a more widespread character and of more grandiose 

 dimensions ; the later testify to a gradual diminution, both in 

 extent and intensity, of volcanic activity. 



The lowermost of these deposits of the Phlegraean Fields are the 

 lavas and pipernoid tuns which may be correlated with the grey 

 tuffs that constitute the entire platform of Campania. These are 

 followed by a series of breccias, conglomerates, and layers of 

 scoriae ; and the whole of this earlier submarine series is overlain 

 by the great masses of yellow tuff, which form the framework of 

 all the hills between Naples and Cum a. 



The eruption of yellow tuff was followed by an uplift, and by 

 prolonged denudation. Later began a series of subaerial eruptions, 

 the products of which were chiefly ashes, lapilli, and pumice (more 

 or less loosely compacted to form grey tuffs), and also a few lavas 

 of trachy-andesitic character. 



These subaerial eruptions took place over a more limited area, 

 internal to, and shifted more southward and seaward than, the 

 earlier eruptions. Not only was there this distinction, but the 

 several volcanoes of the second series diminished gradually in 

 intensity and extension, although this diminution was fitful rather 

 than regular. They began with the great outbursts of the enor- 

 mous ancient crater of Agnano, and died out in the paroxysm of 

 Monte Nuovo. 



In this manner the volcanic fires which, towards the beginning 

 of the Pleistocene Period, glowed with such intensity over the 

 entire Phlegraean area, are now confined to a few localities on its 

 southern shore-line ; and eruptive energy has shifted its centre a 

 little farther southward, to Vesuvius. Volcanic action, which is 

 always associated with orogenic movements, has in this case also 

 followed upon the uplift of the Apennines : an uplift which, 

 beginning in the north, has been subsequently prolonged and 

 slackened off southward. Thus the subterranean fires which first 

 kindled the volcanoes of the Tuscan Maremma and the Agro 

 Romano, passing on by the Islands to the Phlegraean Fields and 

 Vesuvius, have now travelled farther south, to the flaming JEolian 

 Isles, and snowy iEtna, the pillar of heaven. 



