of the Apennines. 161 
but the sand is always the newest of the whole. This sand, 
also the marl, clay, and sandstone, often abound in fossil orga- 
nic remains, among which are bones of colossal sea and land 
animals, and hosts of shells, often well preserved, and which 
have been well drawn and described by Brocchi in his ConcJiio- 
logia Fossile subapennina. 
The calcareous tuffa and volcanic tujfa belong to the more lo- 
cal tertiary formation. The frequent occurrence of the calcareous 
tuffa on the bottom of the valleys, and on the sides of the Appen- 
nines, should not excite surprise, as the greater part of them are 
of limestone. Probably no country in the world exhibits greater 
variety in aspect, and more extensive masses of calcareous tuffa, 
than Italy. Our author attempts to arrange the most important 
of these according to their relative antiquity. Those varieties 
which contain sea-shells, he considers as the oldest. To these 
follow, in order of formation, the calcareous tuffa , found in the 
neighbourhood of Rome and other places, and which is of con- 
temporaneous formation with the volcanic tuffa, as is shewn by 
their alternation with each other. These, and all the other 
newer deposites, contain only remains of fresh water shells, and 
traces of fresh water plants. The considerable mksses of calca- 
reous tuffa which cover the volcanic tuffa, and, according to 
Professor Kayser of Christiania, the remarkable mass of tuffa 
on which Tivoli is built, appears to be of still more recent ori- 
gin. Those formations of calcareous tuffa which are daily ta- 
king place, form the limit of the series of formations of this in- 
teresting substance. 
VonBuch has shewn, that this volcanic kffa 5 although composed 
of volcanic matters, has been brought into its present situation 
by water, and deposited from that liquid. Its masses, although 
considerable, are confined to the south-western side of the Appen- 
nines, where it appears in two principal districts, of which the one 
comprehends the neighbourhood of Rome, and extends south- 
wards towards the Pontine Marshes, and northwards towards 
Civita Castellana , Viterbo , to the vicinity of Bolsena ; the other, 
which is of less extent, occupies the country around Naples. Be- 
sides these, small deposites of volcanic tuffa occur in other places. 
The tuffa varies in its characters even in the same place ; but a 
principal difference occurs between the Roman and Neapolitan 
VOL. ix. no. 17. JULY 1828. L 
