150 ' The Volcanic Rocks of 



it may be stated, that both have the tufa lithoide, or con- 

 solidated stone ash. It is more abundant on the Roman 

 than on the Victorian soil. As a bnilding-stone with both, it 

 has been employed in the most massive and important erec- 

 tions of Italy, and but little in this colony. Piles of it were 

 reared in the Coliseum, and even used in the more ancient 

 Cloaca. Climate and age seem to have no effect upon it. 

 Here I have seen it in church ornaments at Belfast and 

 Warrnambool. Saints' heads, effigies of sovereigns, dragons, 

 and other primeval j)ersonages, inclusive of a volcanic John 

 Wesley reposing on a monster at the Belfast chapel, have all 

 been sculptured out of the Merri Creek tufa. I have seen 

 some chimney-tops, and even substantial walls of stone, 

 of the same material. A little skill is required in its mani- 

 pulation. The strata being horizontal, and not so consistent 

 as the Italian, should not be set up on the edge. A publican, 

 near Mount Shadwell, had faced his house with this easily 

 worked stone ; but having set it up perpendicularly, flakes 

 have been so constantly falling that soon the various leaves will 

 have flown out. 



The Roman tufa litJioide is reddish brown in colour, with 

 much pumice. Most of the Seven Hills contain it. The 

 best quarry, however, is on the road to Albano, about nine 

 miles from Rome. The Mamertine prisons, in which Paul 

 and Peter are said to have been confined, are cut out of this 

 rock. I found St. Elmo dungeons to be excavations in the 

 Naples tufa. This ancient formation is a Peperino, being, as 

 it were, peppered over. That used in the sewer, or cloaca, is 

 a sort called gahina. The Tarpeian rock is very hard and red 

 lithoide. The source of this tufa is not very apparent, and 

 not, probably, in any of the existing craters. Sir R. I. 

 Murchison has supposed that vents discharging ashes may 

 have closed so as not to be distinguished now. 



The more recent beds of tufa were, doubtless, thrown 

 down from the existing craters upon the dry land, and are 

 horizontal in position. The fresher ash contains hardly a 

 trace of pumice, and is of a lighter colour. The lainlli, or 

 small cinders, are in both sorts. Sand-shells and land-plants 

 have been found in the newer sort. That north of the 

 Campagna is whiter and contains pumice. The Peperino of 

 Albano has fossil wood occasionally in it. 



The Pozzolano of Rome is a particular sort of tufa, found 

 in the ash-beds in small quantities, and highly prized for 

 cements ; with the addition of a little lime it forms a good 



