322 EEPOET— 1888. 



Later on yellow tuffs appear again, until at 1,890m. tbe great mass of 

 trachyte, referred to last year, continues for 110m. This will probably 

 be looked upon in future as the most beautiful specimen of sodalite trachyte 

 known, whilst its cavities, where the rock is vesicular, are lined by 

 some six or seven species of minerals. At both ends it is seen to be 

 limited by an escarpment, against which a talus of its own blocks exists, 

 and over these, but similarly inclined, a number of pumice and ash beds, 

 followed by compact tuffs. The remaining part of the tunnel is cut in 

 the compact yellow tuff of the district, except near its mouth, where 

 it is overlaid by the usual loose pozzolana. The same railway traverses 

 the Posilippo ridge parallel to the two existing tunnels, but, like them, 

 traverses compact yellow tuff. 



On the road to Pozzuoli, just beyond the thermo-mineral baths of La 

 Pietra, of Bagnoli, a yellow tuff has been cut down, upon which exists a 

 raised beach composed of large, more or less rounded, masses of the same. 

 In the interpace's between these, as the result of solfataric action, beautiful 

 branched efflorescent masses of gypsum were met with, attached to the 

 surface of the tufa. 



Not far beyond this, a tunnel is in course of construction which runs 

 parallel to the cliif and road, and only a few metres from the surface. The 

 beginning, or Naples end of it, is cut in sand, breccia and gravel constitut- 

 ing the raised beach underlying the trachyte eruptions of the solfatara, 

 and eventually enters the deposits of black scoria belonging to the same. 

 The heat is so intense that work was suspended till the ventilating windows 

 and shafts, now being made, be finished. 



The last point of importance on this line, is the tunnel intended to be 

 cut through the hill of Baja, of which in the last report doubts were 

 expressed as to the practicability. This work has only been commenced 

 a few days, at the entrance beneath the baths of Nero, but the altered 

 pumice in the tuff, deposits of silica in fissures, and a gradually increasing 

 temperature seem pretty sure indications of the difficulties to be con- 

 tended with. 



Collettore Pluviale delle Colline. — The main collector of the pluvial water 

 from the hills backing the west of Naples is now nearly complete. It may be 

 said to run roughly parallel with the Cumana Railway tunnel, but at some 

 distancefromit and at a lower level. In thisamass oftrachyte was traversed 

 for 28m. It differs from both the masses of the Cumana Railway tunnel 

 in some of its characters, but approaches mostly the smaller one to which 

 it is more nearly situated. What is very interesting about it is that its 

 fissures (it is not vesicular) are often lined by beautiful octahedra and 

 pseudoprisms of what was once sodalite, but is now nothing more than a 

 shell, of bright brick-red colour, of a mixture of substances which has 

 replaced the original mineral. In some places the latter is unaltered, 

 and all gradations can be met with in the process. This mineral and its 

 products are accompanied by many needles of titanite, amphibole, some 

 zeolite, &c. This trachyte is enveloped in the Rione Amedeo tuff, but 

 going west this is overlaid by the usual compact yellow tuff, and 

 eventually pozzolana. In the tuff near the trachyte blocks of piperno 

 were met with, and in the Rione Amedeo large masses of grey plastic 

 clay (Pliocene), quite unaltered and containing many fossils. 



Funicular Railway of Rione Amedeo. — This work, composed principally 

 of a tunnel with some open cutting, is placed above and at right angles 

 to the Cumana Railway and the Pluvial Collector, and joins a side adit 



