ON THE VOLCANIC PHENOMENA OF VESUVIUS. 323 



from the former. We have at its lower part Rione Amedeo tuff, super- 

 imposed upon which come beds of pumice and ash, continuous with the 

 well-known synclinal fold of these Ijeds on the Oorso Vitt. Emmanuele. 

 Above this comes the common yellow tuff. 



Funicular Baihvay of Monte Santo. — This is only in the early stages of 

 construction, but is likely to afford very important data for disentangling 

 the complex structure of the Campi Phlegreaj. Entering the tunnel from 

 the Corso Vitt. Emmanuele, some four metres (vertical measurement) of a 

 loose brown pozzolana are met with, in which occur fine-structured, dirty- 

 white pumice. This is overlaid by a bed of small white pumice lapillae 

 without any accessory or accidental ejectamenta superimposed, upon 

 which comes 4m. of similar pumice, interstratified with thin bands of 

 pozzolana of buff or red colour. Upon these deposits we have another 

 greyish-white pumice bed OSOm. thick, and composed of large masses, up 

 to the size of a cocoa-nut. The upper part of this pumice has under- 

 gone a peculiar reddening, which I shall refer to later. Above this 

 is a black ash-band 010m. thick, and then about 4-50m. of grey 

 pipernoid tuff, the lowest 030m. of which is red in colour, and 

 shades into the grey above. This tuff is identical in character with 

 similar tuffs of Sorrento, Nocera, Capua, and Roccamonfina, and con- 

 tained a small block of piperno with large marialite crystals. Super- 

 imposed on this comes 2-50ny. of coarse breccia of reddish pumice with 

 numerous large blocks, consisting of pieces of viti-eous piperno, sodalite 

 trachyte, a bright red vesicular basic rock (andesite ?), pyroxenic lava 

 (dolerite ?), tuffs of various kinds, and pieces of black obsidian. At the 

 opposite or descending end of the tunnel only yellow tuff has, so far, been 

 met with. 



To appreciate the value of these sections, it is necessary to refer to 

 some others in the neighbourhood. The breccia bed in this section is 

 identical with that overlying the piperno of Pianura and Soccavo. The 

 banded ash and pumice beds are identical with some seen underlying the 

 above-mentioned breccia behind Soccavo, and the grey pipernoid tuff is 

 stratigraphically in the same position as the piperno of those localities ; 

 besides, it contained a most characteristic fragment of that rock, made 

 doubly certain by the marialite crystals. The facts, I think, are suEBcient 

 to satisfy anyone that piperno and this grey pipernoid tuff are derived 

 from the same source. But beyond this, at Fossa Lupara, between 

 Nocera and Sarno, this same grey tuff is red at the bottom and reposes 

 on a reddened pumice, like that in the section of Monte Santo 

 Funicular Railway tunnel ; whereas, at the Codola tunnel, near Nocera, 

 a thin bed of white pumice underlies the grey tuff. 



In both these cases the pumice is smaller, and in the latter small in 

 quantity, as if transported aerially from a great distance. These con- 

 clusions immediately bring up in our thoughts the unsettled question as 

 to what is the piperno of Pianura and Soccavo. There it has all the 

 compactness of a lava, with distinct evidence of flow structure in its 

 components. Elsewhere it looks like a tuff. It is supposed by some to 

 be a metamorphosed or refused tuff in places ; but if that were so the 

 underlying pumices at Soccavo should have been similai-ly altered. 

 Besides, at Soccavo, at the west end of the section, two distinct beds of 

 piperno may be met with (I believe so far unnoticed by other observers), 

 interstratified with similar materials as far as heat could influence them, 

 whilst the pipernoid banding of the ejected blocks immediately overlying 



T 2 



