302 PROF. G. DE LORENZO ON THE HISTORY OF [Aug. I904, 



In that area, the work, both destructive and constructive, accom- 

 plished by later vulcanicity has been so manifold and extensive, 

 that it is no easy task to trace the equivalent of the pipernoid 

 tuffs. Nevertheless, a great mass of them has been found, as 

 before described, in the artesian well sunk in the Royal Garden at 

 Naples ; and less considerable remnants are traceable in the depres- 

 sion that lies between the hills of Vomero and Posillipo. Also at 

 Monte di Cuma, immediately above the great dome of trachyte 

 which forms the base of the historic acropolis, and is perhaps 

 contemporary with the piper no presently to be described. 



Instead of the pipernoid tuffs, we find exposed in the Phlegrsean 

 Fields as their representative the celebrated piperno. This forms 

 the base of the Hill of the Camaldoli, and, interrupted here and 

 there, by later deposits of yellow tuff and grey pozzolana, may 

 be traced from the spurs of that hill for about a mile and a quarter 

 eastward into the basin of Soccavo, and for other two-thirds of a 

 mile northward into the basin of Pianura, divided into two beds or 

 layers by an intervening band of breccia. 



The controversy has been a lengthy one, as to whether the 

 piperno should be regarded as a metamorphosed tuff or as a lava, 

 and even now geologists are by no means unanimous on the point. 

 It appears to the present writer, however, that both the geological 

 conditions and the petrographical characters of the piperno are 

 in favour of the conclusion that it is a trachytic schlier en-lava, 

 the dark stripes of which are made up of such minerals as augite, 

 segyrine, and magnetite, while the lighter groundmass is of fel- 

 spathic nature (auorthose), with a spherulitic structure and tiny 

 microliths of aegyrine and augite. It is not claimed, however, that 

 a sharp dividing-line can be drawn between the dark schlieren 

 and the light groundmass. 



The occurrence of the piperno at the base of the Hill of the 

 Camaldoli leads to the supposition that this locality, which is 

 practically in the very centre of the Phlegraean Fields, is also the 

 site of one of the principal vents from which was ejected the 

 pipernoid tuff of Campania. This supposition is strengthened by 

 the fact that at that very same spot great explosive eruptions took 

 place at a later period, to which the superposed bands of breccia 

 bear emphatic witness, not to speak of a considerable ejection of 

 yellow tuff. So abundant indeed was the accumulation of eruptive 

 material, that it served to build up the present Hill of the Camaldoli, 

 which, despite successive demolitions and degradations, still forms 

 the most conspicuous elevation in the Phlegrsean Fields. 



(b) Phase of the Conglomerates and Breccias. 



Above the piperno and the pipernoid tuffs comes a succession 

 of strata diverse in character, it is true, but predominantly con- 

 glomeratic, and bearing visible traces of the flow of sea-currents 

 and of marine deposition. Whence it may be inferred that, equally 



