324 BEPORT— 1888. 



them is oriented in all directions, a fact sufficient to negative all qnestion 

 about refusion or metamorphism, unless this took place on the surface of 

 the ground. Lastly, pieces of peculiar yellow tuff enclosed in the massive 

 piperno, in the overlying breccia blocks atPianura, at Soccavo, and aleo at 

 Naples, are quite unaffected by fusion, or changed more than what would 

 occur by being caught up in a quickly cooling lava stream. Two expla- 

 nations remain open to my mind. First, piperno is a true lava, of which 

 the grey tuffs are the cinders and ashes of the more explosive stage of the 

 eruption or eruptions. Against this we have the stratified structure o-f 

 piperno, independent of its banding due to the presence of more or less 

 in number of the enclosed blacker lenticles, and secondly, the long, thin 

 bed of uniform thickness of the upper piperno of Soccavo. Secondly, the 

 eruption of magma towards the end or at the beginning of an eruption, 

 fairly free from aqueous inclusion, which, falling still hot, became more or 

 less fused together in the immediate neighbourhood of the vent, as may be 

 seen at any active volcano. In favour of this we have the fact that often 

 the piperno appears to be composed of fragments in part fused together, 

 as if the heat were insufficient to complete the operation. In both cases 

 we must suppose a mixture of two magmas. They may, however, be 

 nothing more than the same one, part from the upper, cooler portion of 

 the chimney and part from the lower, hotter and more aquiferous, just 

 as in the banded trachytes of Palmarola. This is supported by the ejected 

 blocks having the black part composed of obsidian, whilst the grey is 

 much more vitreous than the massive rock. 



To limit this report, the remaining conclusions are given categorically, 

 open to correction in the studies to be published in full : — 



The oldest rocks, so far known in mass near Naples, are the sodalite 

 trachytes of the Cnmana tunnel. These are overlaid by the Rione 

 Amedeo tuffs, probably the explosive eruptive products of the same 

 magma. 



This is followed by the Pianura volcano, all the southern part of 

 which has been destroyed by later explosive eruptions, and by the erosion 

 of the sea, which deposited the raised beach of the Lucrine Lake, ruined 

 the south of Monte Barbaro, deposited the Starza Cliff and the raised 

 terrace of Stabia and Castelammare. 



That this volcano was the main mouth (perhaps with others) from 

 which was derived the grey tuff of the Campania, Terra di Lavoro, &c., 

 and the breccia beds, and to which belongs the lapillo bed near theParco 

 Grifeo of the Corso Vitt. Emmanuele. 



That the eruptions of Roccamonfina were earlier than the eruptions of 

 the Pianura volcano, but that Vesuvius was in great pai't later, because 

 no signs of grey tuff can be met with in the A trio section, and because 

 the nearly complete series of Somma pumices can be seen overlying the 

 grey tuff at Nocera. 



That volcanic activity has followed a regular course southwards on 

 the mainland of Italy. 



That the yellow tuff of Posilippo, &c., is later than these deposits upon 

 which it is superimposed, thus constituting, with the underlying segment 

 of the Pianura volcano, the highest point near Naples, that is Camaldoli. 



And that in all probability these yellow tuffs were derived, in part at 

 least, from the Monte Barbaro and Campiglione volcano. 



That any attempt to study the sequence of magmas in such a region 

 is impossible till the whole history is carefully marked out, as shown by 



