126 Mr Forbes's Physical Notices of the Bay of Naples. 



lak remarks*, with most of the craters of the Phlegraean fields 

 in that peculiarity of structure. The height of this plain, 

 which occupies the interior of the crater, is 291 French feet, 

 = 310.2 English, above the sea, of which the bounding walls 

 are steep towards the inside, particularly in the eastern quar- 

 ter, where the Monte Olibano boldly rises and stretches down- 

 wards to the sea, forming a point of great boldness, through 

 which the road has been cut a short way from Pozzuoli, be- 

 tween that town and Naples. 



The exterior flanks of the crater are less abrupt, joining, as 

 we have said, in some places with the ridges which surround 

 it. From the spring of the Pisciarella on the side next the lake 

 Agnano the ascent through the ravines there formed by tor- 

 rents is rather fatiguing. Before we advert more particularly 

 to the structure and phenomena of the Solfatara, we may take 

 a glance of its previous history, and the probable changes 

 which it has experienced within the memory of man. 



As far back as the time of Strabo it was known by the 

 name of H^a/?^? Ayo^a, or " Forum Vulcani,*" and his de- 

 scription corresponds very well with its present condition. 

 Pliny ,-[• in speaking of the qualities of sulphur, mentions among 

 the sources whence it is procured one, which can only refer to 

 the Solfatara; he says "in Italia invenitur in Neapolitano 

 Campanoque agro, collibus qui vocantur Lcucogaei ;'' the 

 spot before us being the only one in this range of hills which 

 affords sulphur in a commercial quantity. A famous passage 

 of Petronius Arbiter commencing " Est locus exciso penitus 

 demersus hiatu,*" is too well known as a poetical picture of this 

 scene in describing the infernal regions to require quotation ; 

 but the most satisfactory account of the ancient condition of 

 this crater is in the short passage of Cornelius Severus, placed 

 as a motto to this paper, in which the term " multis jam fri- 

 gidus annis" cannot be supposed to exclude the idea of the 

 production of sulphur, but merely in allusion to the formerly 



• Essais Mineralogiques sur la Solfatare de Pozzuole. 8vo. Nap. 1792, 

 p. 17. The measurements are also taken from this work, as Breislak had 

 the best opportunity of deterrahiing the size. Soulavie makes it only 1500 

 feet by 1000, and Ferrari gives 1100 palms for the greatest length. 



t Hist. Nat. lib. xxxv. cap. 1 5. 



