EARLIEST VOLCANIC OUTBURSTS 321 



period, the first mutterings, as it were, of the sub- 

 terranean convulsions, been more instructively preserved 

 than in the line of quarries that have been opened 

 along the edge of the alluvial plain of the Tiber at 

 the Torretta di Quinto, near the Ponte Molle, about 

 two miles north from the city. The section of strata 

 there exposed, which has long been known and often 

 described, is at present undergoing rapid changes from 

 the extensive excavations required to procure materials 

 for the embankment of the river in its course through 

 Rome. Nowhere, too, is the geologist more seduc- 

 tively wooed from the pursuit of his researches 

 by the fascination of crowded historic associations. 

 From the slopes above the quarries, he sees the Tiber 

 catching the shadows of the Pons Milvius, where 

 Maxentius met his doom. v Below him rise the roofs 

 of the Osterie, which on feast days repeat the noise 

 and merriment that made the place notorious in the 

 days of the Empire. Opposite him, a green hill 

 marks the long-deserted site of Antemnae, beneath 

 which the Tiber winds as a silver band through its 

 meadows far up past other old towns that have long 

 since mouldered into dust. Looking across the green 

 and purple expanse of the Campagna, dotted with its 

 ruined towers, he sees the whole sweep of the blue 

 rampart of the Sabine Hills almost the only feature 

 of the landscape that has remained the same. If from 

 these memories of the past he turns to the long line 

 of quarries, he is perchance rudely awakened to the 

 strenuous present by gangs of workmen, digging, 

 blasting, wheeling ; by the rattle of laden wagons, 

 and by an occasional explosion of gunpowder or 



