310 PROF. G. DE LORENZO ON THE HISTORY OF Allg'. I904, 



crater of accumulation of Astroui and its internal cones. A third 

 sequence, in part excentric and in part concentric, is furnished by 

 Monte Gauro, the explosion-crater of Teano, and those of A vermis 

 and Monte Nuovo. Excentric sequences, on the other hand, are 

 exemplified in the crater of Astroui, as well as in the volcanoes of 

 Cigliano and Campana which have arisen on its shoulder ; and 

 similarly in the volcano of Monte Gauro, with the subsidiary cones 

 of Concola and Fondo lliccio, which are placed parasitically on its 

 western flanks. 



All these concordant sequences demonstrate, not 

 only that eruptive activity was gradually diminish- 

 ing, but that it was in general contracting towards 

 the centre of the volcanic area; or rather, that it was 

 shifting southward and seaward, receiving from the 

 waters of the ocean the kinetic factor, steam. 



But, leaving aside these theoretical considerations, it may be well 

 to describe as briefly as possible the chief among the latest volcanoes 

 of the Phlegra)an Fields. 



The Volcanoes of Grey Tuff. 



The greatest and most ancient of the third series of the volcanoes 

 of the Phlegraean Fields is that of Agnano. Its broad and deep 

 crater, about 1| miles across, is all but intact on the east, but is 

 partly demolished and partly masked on the west by later outbursts, 

 such as those which have originated the successive volcanoes of 

 Astroni and the Solfatara. The materials of which Agnano is built 

 up, like those of the later volcanoes, consist mainly of layers of 

 pumice, ashes, lapilli, and soft grey tuffs, among which, on the 

 eastern and southern flanks (Monte Spina), are also intercalated 

 beds of scoriae. With this volcano we may too, in all probability, 

 associate the great mass of trachy-andesitic lava of Caprara, 

 which, torn asunder and then mantled over by the later eruptions 

 of Astroni, is now involved in the eastern flank of the last-named 

 volcano. From the internal eastern flanks of Agnano thermal 

 mineral springs well forth in great abundance. These are now 

 canalized, and debouch by artificial channels into the sea. But 

 about fifty years ago they united to form at the bottom of the crater 

 a broad and shallow lake, wherein was deposited the detritus carried 

 down from the slopes by rainwash. It was in consequence of the 

 occurrence of these thermal springs, and of the exhalations of steam 

 and gas associated with them, that the ancient Romans created here 

 great baths, which might be successfully restored. 



West of Agnano arise the volcanoes of Astroni and the 

 Solfatara, the relative antiquity of which it is at present 

 impossible to determine. The materials of the Solfatara have been 

 completely altered by copious gaseous exhalations. Xow, as such 

 altered materials are seen underlying those of Astroni, it may be 

 reasonably argued that the earlier eruptions of the Solfatara were 



