E 36 ] 
granite with, the hill, and is the only one in thofe parts ; 
the common \mlcanic tradls affording nothing fimilar. 
Having dwelt fufiiciently on this group, in the begin- 
ning of my paper, I fhall briefly add a few obfervations. 
on the phyfical topography of Monte Roffo itfelf, with 
an account of fome other of its vulcanic produdfions, not 
lefs curious than the group of columns before defcribed^ 
Monte Roffo is ifolated from the principal chain of the, 
Euganean hills, of an orbicidar form, andmeafures about 
a mile and a half in circumference at the bafe.. It con- 
lifts principally of gray granite, which is difpofed in, 
blocks, and irregularly’perpendicular Jirata. I have al- 
ready mentioned the quality of this granite, and its re- 
femblance with that, of Auvergne and Velay. Towards 
the.furface of Monte Roffo, it appears fometimes rotten, , 
or friable, and. porous, as it were, , like a motley kind of 
lava^ which I have frequently feen. But I was furprifed, ^ 
on examining the granite maffes of Monte Roffo, to find 
in them pieces of common.porous brown lava-, which , 
did not appear to be cafually lodged there, and of extra- . 
neous origin, (like the rounded pebbles in. pudding.,ftone, , 
and other aqueous Jirata) hwt manifefllyfeemedto form 
integral parts of the mafs itfelf, and to have concreted . 
with it at tho fame time. . Lobferved a fimilar fort of po-- 
rous lava., but of a black colour,, in the granite of the 
caftle hill at Moncelefe, near Efle, at theTouth eafl fkirt . 
of the Euganean hills ; and I. doubt not but the fame is 
common to others.. This fadf, added to many others, 
which I fhall not infift upon at prefent, feems flrongly 
to 
