332 THE ROMAN CAMPAGNA 



and Stromboli do now, would be subject also to 

 continual erosion by rain and to unceasing attack 

 along their shores by wind-waves. They would thus 

 tend to be ultimately planed down, their materials 

 being strewn over the surrounding sea-bottom, so 

 as to add to the general accumulating sheet of tuff. 

 The rapidity with which this kind of demolition may 

 be completed was impressively exemplified in this 

 very area of the Mediterranean by the history of 

 Graham Island, which in the summer of 1831 was 

 thrown up by a submarine eruption off the southwest 

 coast of Sicily. In the course of less than a month, 

 a cone of loose cinders, scoriae and pumice was piled 

 up to a height, it is said, of more than 200 feet above 

 sea-level, with a circumference of three miles and a 

 large crater inside. In about three months, this 

 volcano was levelled with the surface of the sea. 



As a consequence of the prolonged eruptions, the 

 sea along the west coast of Central Italy must have 

 become increasingly shallow. This result may not 

 improbably have been expedited by that uplift of the 

 whole region to which reference has above been made. 

 In course of time, not only would volcanic cones 

 appear as islands above sea-level, but the action of 

 winds, waves and tidal currents would throw up bars 

 or lidiy like those of Venice or those of more ancient 

 date which traverse the alluvial plain on either side 

 of the mouth of the Tiber. Further deposition of 

 sediment, either from the volcanoes or from the 

 torrents of the Apennines, would lead to the silting 

 up of the lagoons between these bars. The hollows 

 on the newly gained land would eventually become 



