on the Materials used in the city of Home. 39 



mentions as employed for vaults and cupolas on account of 

 its lightness, has occasioned some discussion. He says "questa 

 pietra traevasi dalle vicinanze del Vesuvio, 1 ' and mentions no 

 authority for the circumstance of its being carried all the way 

 from Vesuvius. Nibby appears to be no mineralogist himself; 

 and I am inclined to suspect, that, knowing of no pumice near 

 Rome, he supposed that it was brought from that volcano. 

 Now pumice is by no means an abundant production of Vesu- 

 vius. Dolomieu (Isles Ponces, p. 31, note,) confesses, that in 

 a cursory view of the environs of Naples, he was not aware of 

 the existence of pumice there, and Breislak mentions its occur- 

 rence, (Campanie, vol. lre,J only in one place of the moun- 

 tain, though it is more frequent in Ischia.* It was doubtless 

 from a knowledge of this rarity of pumice, that made the 

 editor of the Journal in which Mr C. T. Ramage's translation 

 of Nibby appeared, remark in a note, " The pumice mention- 

 ed above is, we presume, vesicular lava, not the pumice of 

 geologists."" Now pumice is a substance so perfectly well known 

 in Italy, that it is extremely improbable that it should be con- 

 founded with the other substance, (though by ignorant fo- 

 reigners it sometimes is,) by Sig. Nibby, (Mr Ramage's name 

 it of course does not rest upon, being a mere cypher,) though 

 indeed nothing but an inspection of the vaults of the Colisseum 

 and royal palace to which that gentleman refers, can properly 

 decide the question, and my memory does not so far serve me 

 in the present case. But I think it, on the whole, much more 

 probable that it is a true pumice, since it is found much nearer 

 than Mr Nibby imagines, namely, in the very Campagna di 

 Roma. My authority is the testimony of Brocchi, (Suolo 

 di Roma, pp. 203, 204 5> ) whose words I literally translate. 

 " In these places" near the Sepolcro dei Nasoni, &c. near 

 Rome, " pumices are most abundant, which are sought in 

 vain on the mountains of Albano and Tuscolo ; and they be- 

 come much more abundant as we proceed northward from 

 Rome. At the issue of the Acqua-traversa, on the road to 



* I have in my possession a specimen of pumice from Vesuvius,, and 

 another from Cumae. It is extremely rare in Etna. See Spallanzanis 

 Travels, and Dolomieu, Catalogue desproduits d' Etna. Most of the pumice 

 of commerce comes from Lipari. 



