No. III. — PausUipo and the Lago (TAgnano. 263 



oxygen of the atmosphere, form water on the one hand, and 

 deposit part of the sulphur, and, on the other, sulphuric acid 

 is produced; or rather, according to Daubeny, hypo-sulphur- 

 ous acid. Monte Secco forms the eastern boundary of the 

 hill of the Solfatara, and will therefore come to be considered 

 as to structure in a more general manner afterwards. - 1 may 

 mention, however, that its basis seems to be principally decom- 

 posed lava, which assumes a white and plastic condition, being 

 a union of felspar and silex in a minute state of division. The 

 vapours of the Pisciarella seem to cause the most compact 

 lavas to exfoliate with great ease, the constituents of which, 

 suspended in the water, are deposited, according to Breislak, 

 in beds of clay and siliceous sinter. The range of hills of 

 which Monte Secco forms a member, seem to have been named 

 by the ancients Colles Leucogaei; and Pliny* mentions waters 

 good for the eyes, as existing between Puteoli and Neapolis, 

 under the title of Fontes Leucogaei, which some have imagined 

 were identical with the Pisciarella ; but Breislak shrewdly re- 

 marks, that, from the component parts of this , spring, we 

 should not be tempted to consider it a very salutary lotion for 

 the eyes.-[- 



We shall now shortly notice the last conspicuous feature of 

 the interesting circuit to which this paper limits us. The val- 

 ley, or rather basin of Astroni, lies to the north of the Lake Ag- 

 nano, and between the hills of the Solfatara and the Camal- 

 doli. It is one of the best marked- extinct volcanic craters 

 in existence, and besides, one of the most agreeable spots 

 \ ' in the whole range of the Bay of Naples. It is a hollow in a 

 truncated cone like a regular volcano, and its size has been 

 variously estimated, apparently from the small attention 

 which this delightful spot has excited, so that probably 

 few of the visitors at Naples have ever approached it, as the 

 guide-books rai'ely mention it, or leave it out altogether. 



• Nat. Hist. lib. xxxi. 2. 



t The fountains mentioned by Pliny were probably similar to those 

 which rose in the academic villa of Cicero, and which have b^en recorded 

 in verse by his freedman Tullius: — 



Hinc etiam apparent lymphae non ante reperta^, 

 Languida quae infuso lumine rorc levant. 



