Mr. PouLETT ScROPE oTi the Volcanic District of Naples. 351 



seen from the foreg^oing account, the volcanic hills of the neighbourhood of 

 Naples are almost exclusively formed, seems evidently to owe its coherence, 

 like the trass of the Rhine provinces, to a setting, or aggregative process 

 which took place in a body of finely triturated trachyte intimately mixed with 

 water, as that fluid drained off, or was squeezed out by the incumbent pres- 

 sure. In the formations under review, this admixture with water appears to 

 have been owing to the circumstance of the volcanic vents having burst out 

 under the level of the sea, though in so shallow a spot that the accumulated 

 ejections soon raised the cones to a certain height above the water-level ; in 

 consequence of which the materials subsequently thrown up, falling dry on 

 the surface of the newly-raised island, remained in a loose state. Every one 

 of the hills in question is indeed covered to a greater or less depth by strata of 

 loose tufaceous conglomerate, conformable and sometimes graduating into the 

 hard tufa below. The Monte Nuovo, which was thrown up in the middle of 

 the Lucrine lake, has, like the other hills, a foundation of indurated tufa 

 covered by loose conglomerate. The same loose arenaceous conglomerate, 

 but evidently stratified by water, composes the flat spaces between the volcanic 

 hills, and also the surface of the whole plain of the Terra di Lavoro, up to 

 the foot of the Apennines ; penetrating even their principal valleys to a consi- 

 derable height, — as for example those of Maddeloni, Caserta, &c., — having 

 to all appearance been drifted there by the sea at a time when it washed the 

 base of that chain. 



It seems then that this part, at least, of the western coast of Italy has suf- 

 fered an elevation of some hundred feet since the epoch of eruption of the 

 greater number of volcanic mouths whose products we have been employed 

 in examining, and which are certainly much more recent than the tertiary or 

 subapennine formation. In this elevation, it is at \e2iSi probable that the whole 

 chain of the Apennines shared ; and indeed there are traces of it in the lime- 

 stone cliffs of the Monte Circello and the Calabrian coast, which are in 

 some parts thickly perforated by recent lithophagi at a height of more than 

 a hundred feet from the present level of the sea*. 



Whether this elevation took place at once, or by successive heavings ac- 

 companying the earthquakes which have habitually affected the Western Apen- 

 nines, from Rome to Palermo, is a question which it requires further inquiries 

 to elucidate. From my own observations, I should be inclined to doubt that any 

 sensible change has taken place in the relative level of the land and water 

 round Naples since the Roman asra, (the few facts which have been brought 

 forwards to support the idea of such change being contradictory, and to be 



* See Brocclii, Cat. rag. passim, and Bibl. Ital. 1822. 



