XIV. — Notice on the Geology of the Ponza Isles. 

 By G. Poulett SCROPE, Esq. F.G.S. 



[Read April 23d, May 7th and 21st, 1824.] 



All the islands that rise from the Mediterranean olTthe coast of Terracina 

 and Gaieta are often designated as the Ponza Isles; from the name of the 

 central and largest amongst them *. 



It would be more correct^ however, to consider the three most westerly 

 isles, viz. Ponza, Palmarola, and Zannone, together with the minor insulated 

 rocks that are scattered round them, as one group, and Ventotiene and San 

 Stefano, which are separated from these by a considerable interval, very little 

 less indeed than that which divides them on the other side from Ischia, as a 

 second. These islands are all subject to the crown of Naples. Two only are 

 permanently inhabited or in cultivation, Ponza and Ventotiene. The former 

 has a small but deep and extremely secure port; though a number of half-con- 

 ceaied rocks and sunk ledges near its entrance render it dangerous of ap- 

 proach to vessels of burden unless with an experienced pilot. To the small 

 craft that [)ly between Genoa and Naples, it afibrds an invaluable refuge in 

 the rough and variable weather for which the Tuscan sea has been always 

 notorious ; and the more important from the perilous character of the whole 

 western coast of Italy, which from Orbitello to Naples consists of a sandy shore, 

 shoaling gradually to a great distance into the sea, upon which a current 

 constantly .setting towards the land produces a violent and destructive surf. 



In fact a number of boats are annually lost upon this shore, which may be 

 compared to the coast of Lincolnshire, or still more correctly to the low shore 

 of Africa between Cape Blanc and the Canaries. Under such circumstances, 

 the harbour of Ponza, situated in deep water, and at sufficient distance from 

 the main coast to prevent risk in running for it, is probably the means of 



* Pliny (llisl. Miirid. lib. iii. cap. 6. and lib. xxxii. cap. 11.) mentions Ponza, and Ventotiene 

 (anciently Ptiiuluturia or Pandateria) by the appellation of Pontiw Insulce. They are aho 

 mention<(l bv l>ivy. Diodorus Siculus, Strabo, Pomponius Mela, Buno in his notes to Cluverius, 

 and others.— See the Map of this group, PI. XXill. 



