408 REACTION OF THE INTERIOR OF THE EARTH 



which might have served Spartacus ( 55S ) and his gla- 

 diators as a rampart. 



Diodorus Siculus (lib. iv. cap. 21, 5), who lived under 

 Caesar and Augustus, in describing the battle of Her- 

 cules with the Giants in the Phlegrsean Fields, also 

 designates " the Mount " now called Vesuvius, as a \6<f)o$, 

 which, like Etna in Sicily, once emitted much fire, and 

 (still) shows traces of ancient burning. He gives the name 

 of Phlegrsean Fields to the entire space between Cumae 

 and Neapolis. as does Polybius (lib. ii. cap. 17) to the still 

 larger space between Capua and Nola ; while Strabo (lib. 

 v.p. 246) describes the district near Puteoli (Dicsearchia), 

 where the great Solfatara is situated, with great local 

 truth, and terms it 'H^at'orou wyopd. In later times 

 the name ra ^>\s^pata TrsBla has been commonly limited 

 to this district, as in the present day geologists still 

 place the mineralogical composition of the lavas of the 

 Phlegrsean Fields in opposition to those of the district 

 round Vesuvius. We find the same opinion, that in 

 former times there had been fire under Vesuvius, and 

 that that mountain had anciently had eruptions, in 

 Vitruvius's book on Architecture (lib. ii. cap. 6), and 

 expressed in the most decided manner in a passage 

 which has not been sufficiently regarded. " Non minus 

 etiam memoratur antiquitus crevisse ardores et abunda- 

 visse sub Vesuvio Monte, et inde evomuisse circa agros 

 flammam. Ideoque nunc qui spongia sive pumex 

 Pompejanus vocatur, excoctus ex alio genre lapidis, in 

 hanc redactus esse videtur generis qualitatem. Id 

 autem genus spongiae, quod inde eximitur, non in 

 omnibus locis nascitur nisi circum ^Etnam et collibus 

 Mysiae qui a Graecis KaraKsicav^si'oi nominantur." As, 



