HAKDWICKE'S SCIENCE-GOSSIP. 



217 



EAMBLES AMONG THE MODEEN VOLCANOES OE ITALY. 



No. 2. 



^'^™^' EIELDS.— 

 The district 

 ■which received 

 this Grecian 

 (■tMypa) name 

 on account of 

 its fiery appearances, and 

 which is so often referred to 

 in the classic poets as the 

 scene of giant and god wars, 

 is situated on the northern 

 side of the Bay of Naples, and 

 has few rivals either in beauty 

 or interest. Naples, with 

 Vesuvius and the buried cities 

 of Herculaneura and Pompeii 

 to the south, and the Phle- 

 grfean Eields to the north, 

 becomes indeed such a centre 

 of attraction, that few places 

 can surpass it. At first we 

 will confine our attention to some of the chief 

 points of geological note north and west of Naples. 

 Erom the hill upon which the Castle of St. Elmo 

 is built we look across the blue bay to Vesuvius 

 and Sorrento in one direction, and in another down 

 on to the main mass of the city, surrounded on all 

 sides but one by an encircling ring of hill, of which 

 the rock of the Castle of St. Elmo forms a part. 

 On an examination of this encircling hill, it is found 

 to consist of beds of ash of a light yellow or white 

 colour, dipping outwards or away from the inclosed 

 hollow ; in fact, the first glance reveals ihe curious 

 fact that Naples, a city of some 500,000 inhabitants, 

 is built in great part within an old broken-down 

 volcanic crater. 



The whole tract of country, from Naples on the 



east to Cumse on the west, is one mass of craters, 



some fresh and young-looking, others worn down 



aud almost obliterated ; some large, others small ; 



No. 106. 



some having their interior clad with vineyards or 

 wood, and richly cultivated, others inclosing a 

 calm and peaceful lake; but all interfering with 

 one another more or less, old craters being destroyed 

 in the formation of new ones, and all presenting the 

 general structure of beds of pumice-tuff dipping 

 away on all sides from the central orifice. The 

 country presents, in fact, a universal blistered sur- 

 face. Passing from the city through the long 

 tunnel of Posilipo, in which are seen strata of 

 stratified volcanic ash, a short drive brings us to 

 the Lake of Agnano, now, — alas for the scenery ! — 

 being drained into the Mediterranean.* This is a 

 crater-lake, similar in all respects to those already 

 mentioned near Rome, and though apparently all 

 is peaceful, and the waters of the lake reflect its 

 well-wooded and picturesque banks, yet there are 

 ever rising in bubbles through the water and from 

 fissures around the edge, volumes of carbonic acid 

 gas and sulphureous vapours, pointing to some 

 energetic processes still going on beneath, and to 

 the force, present still, but hidden. The volumes of 

 carbonic acid gas rising from a fissure in the well- 

 known Grotta del Cane, are very decided witnesses 

 of some inward calcining process at work. It is 

 highly instructive to walk from this crater-lake to 

 the crater of Solfatara. The path lies among vine- 

 yards planted in the white powdery soil till near 

 the outer edge of the crater. On all sides are deep 

 stream-courses cut out sharply in the soft white 

 felspathic ash, and every section on ascending 

 shows the hill-side to be made up of beds of the 

 same fine crumbling ash, some of it in very thin 

 layers, and dipping markedly outwards. It is 

 important to notice the great regularity and fine- 

 ness of bedding of some of these ash-beds, which in 

 any other situation would at once be put down as 

 clearly evidencing their stratitlcation beneath water ; 



* Probably by this time the draining operations are com- 

 pleted. 



