Professor Moffmann wi the Alban Hills. ^75 



ami forms the Campi (TAiiuibale of the Roman citizens. Not 

 merely the form, however, but also the internal structure, go to 

 prove that this was formerly the site of a crater of eruption. 

 We no longer meet with the peperino^ with the basaltic plateaux 

 of the outer circus, or the crater of elevation. Its principal mass 

 consists of an accumulation of angular fragments of slags, and 

 beds of ashes, as is very well seen on the fresh sections of the 

 Madonna del Tufo. At intervals we find large coarse masses 

 of rough leucite lava, so that the geologist can never hesitate a 

 moment regarding the true nature of the internal mass of the 

 Alban Hills, when once he has seen the fresh thrown up scoria- 

 ceous cones of Vesuvius and Etna. This mass is not, how- 

 ever, every where distinctly separated from the margins of the 

 crater of elevation. On the south and south-west sides, towards 

 Nemi and Palazzola^ they are amalgamated together, and the 

 nearly horizontal beds of peperino between Aricia, Genzano, 

 Palazzola, and Nemi, form a sort of platform which is applied 

 immediately to the sides of the Monte Cavo. It is here that we 

 meet with the beautiful funnel-shaped cavities of the Lago d£ 

 Nemi and the Lago di Castello. The}' bear much resemblance 

 to mere sinkings of the earth, and have certainly never been cra- 

 ters, for the strata are not directed concentric to their margins. 

 Their banks consist also chiefly of peperino, which sinks toward 

 the south into the level tufaceous plains of Rome. 



These views, which I have ventured to lay before you some- 

 what in detail, are perhaps not unworthy of your attention ; but 

 I beg your indulgence for having drawn them up merely from 

 memory, without reference to the chart to which I have alluded. 

 When I get my notes, which have been left behind at Naples, 

 I will be able afterwards to give more minute particulars. I 

 hope also, that it will be in my power to revisit these localities, 

 in order to give sufficient completeness to my observations, that 

 I may be able to form a geognostic chart with the necessary 

 sections. 



Allow me now to transport you to the memorable Phlegrsean 

 fields of Sicily. You may easily suppose, that ever since my 

 arrival in the island, Etna has claimed my especial and almost 

 exclusive attention. In fact, the investigation of this mountain, 

 and of the volcanic phenomena in the neighbourhood, has now 



