156 Th^ Volcanic Rocks of 



But though I could not refrain from emotion as I trod the 

 Appian Way, furrowed by chariot- wheels, it is probable that 

 the lava pavement, along which Paul was borne a prisoner, 

 lay still beneath me ; such being the opinion of some 

 learned antiquarians. 



Black lava issues through the red tufa of Lake Bracciano, 

 while a porphyritic lava pierces the limestone of Mount 

 Catimi. Great masses of lava fill the camp of Hannibal 

 at Monte Cavo. There is some very ancient trachytic 

 rock in Rome. The Albano lava I found to be as varied as 

 the ash. Some specimens were dark, heavy, and of a basaltic 

 character, while others were light and s coriaceous. There 

 were pieces like our own brilliant stone of Leura, sparkling 

 with gems. 



I have not heard of basaltic columns nearer Bome than 

 Mount Radicofani, on the borders of Tuscany. The Roman 

 lava is not so rich in minerals as that of Naples. The 

 ancient rocks of Monte Somma are said to have a variety of 

 above forty minerals. The lava shares with travertine and 

 tufa the honor of erecting the glorious monuments of old 

 Rome. 



In Victoria, to the westward, the lavas are very varied in 

 sort. The party-coloured, bright bunches of crystals, in the 

 augitic lava, give Mount Leura the palm for beauty. The 

 effect is very striking, with the setting sun illuminating the 

 thin, lofty wall of the crater. I gathered blocks from the 

 Green Hill of Ararat, having all the look of those from the 

 Solfatara of Italy ; while the green lava of Wickliffe is 

 rare in Rome. Plain basalt forms the floor of our Western 

 Plains, though scoria is the principal rock of our extinct 

 craters. The decomposition of this rock may vary more 

 fi'om constituents than age. Some hills preserve their vitri- 

 fied appearance, with sharply defined edges, while others 

 lose then' outline in the red earth of decay. The sea wall, 

 near Portland, is so decomposed by the weather that it 

 assumes the character of variegated clays, except the shot- 

 like protuberances remaining from the amygdaloidal basalt. 

 Some of our lavas, as the more consohdated basalts near 

 Melbourne and Ballarat, and on the plains, are probably of 

 submarine origin ; while- others, especially toAvards the 

 south-western part of the colony, are clearly subaerial. We 

 have here, as in Rome, limestone nodules mixing with our 

 lavas. Such are seen at Mount Gellibrand, west of Geelong, 

 as well as at Mount Gambler. Trachyte is at Wangoon, 



