TRUE VOLCANOES. 429 



places, only around ^Etna and on the hills of Mysia, which 

 are called by the Greeks KaraKeKavpevoi.) Now, it can no 

 longer be doubted, since the investigations of Bockh and 

 Hirt, that Vitruvius lived in the time of Augustus, 36 and 

 consequently a full century before the eruption of Vesuvius, 

 at which the elder Pliny met his death. The passage thus 

 quoted, therefore, and the expression pumex Pompeianus 

 (thus connecting pumice-stone with Pompeii), present a 

 special geological interest in relation to the question raised 

 as to whether, according to the acute conjecture of Leopold 

 von Buch, 36 Pompeii was overwhelmed only by the pumiceous 

 tufa-beds thrown up on the first formation of Mount Somma; 

 these beds, which are of submarine formation, covering in 

 horizontal layers the whole level between the Apennine 

 range and the west coast of Capua as far as Sorento, and 

 from Nola to the other side of Naples, or whether Vesuvius 

 itself, entirely contrary to its present habit, ejected the 

 pumice from its interior. 



Both Carmine Lippi, 37 who (1816) describes the tufa 

 covering of Pompeii as an aqueous deposit, and his ingenious 

 opponent Archangelo Scacchi, 38 in the letter addressed to the 

 Cavaliere Francesco Avellino (1843), have directed attention 

 to the remarkable phenomenon that a portion of the pumice 

 of Pompeii and Mount Somma contains small fragments 

 of chalk which have not lost their carbonic acid, a circum- 

 stance which, on the supposition that they have been exposed 

 to a great pressure during their igneous formation, can 

 excite but little surprise. I have myself had the opportunity 



35 At all events Vitruvius wrote earlier than the elder Pliny, as is 

 evident, not merely because he is three separate times cited by Pliny 

 in his list of authorities, so unjustly attacked by the English translator 

 Newton (lib. xvi, xxxv, and xxxvi), but because in book xxxv, cap. 14, 

 s. 170 172, as has been distinctly proved by Sillig (vol. v, 1851, 

 p. 277) and Brunn (Diss. de auctorum indicibus Plinianis, Bonnae, 1856, 

 pp. 55 60), a passage has actually been extracted from Vitruvius by 

 Pliny himself. See also Sillig's edition of Pliny, vol. v, p. 272. Hirt, 

 in his Essay on the Pantheon, places the date of Vitruvius's writings on 

 Architecture between the years 16 and 14 of our era. 



36 Poggendorff s Annalen, Bd. xxxvii, s. 175 180. 



3 ^ Carmine Lippi : Fu il fuoco o Vacqua eke sottcrd Pompei ed 

 Ercolanol (1816) p. 10. 



'& Scacchi, Osservaziom cntichc sulla maniera come fu seppcllita 

 fAntica Pompei, 1843, pp. 810. 



