Site of the Ancient City of the Aurunci. 249 



two, streams of lava ; but the volcanic processes would seem 

 to have soon been transferred to some other quarter, as, from 

 a period long antecedent to historical records, it has sunk 

 into complete inactivity. 



Thus we observe, in these three mountains, three succes- 

 sive developments of volcanic activity evinced, — 



1st, In the elevation of an entire mountain. 



2d, In this elevation being accompanied by the protrusion 

 of a trachytic rock through its centre. 



3fl?/y, In the elevation of a mountain being followed, after 

 a long interval of apparent tranquillity, by the establishment 

 of a permanent vent, through which lavas, fragments of 

 rocks, and elastic vapours, continue from time to time to be 

 discharged. 



All these, however, are derived from subaereal volcanoes, 

 having been formed on dry land, under no greater pressure 

 than that of the atmosphere, and are, consequently, of later 

 date than the beds of tuff which are spread on all sides 

 around them, the latter being products of the action of vol- 

 canoes which existed when the country was yet under the bed 

 of the Mediterranean, and, consequently, being modified in 

 their characters and structure, by admixture with the sea- 

 water in which they appear to have been deposited. 



Appendix I. 



