272 Dr. Mae Culloch on the 
together with the horns of stags; and to these must be added 
vegetable remains, consisting of the trunks and fragments of 
trees, together with leaves but little altered, fresh-water shells, 
and, lastly, fragments of travertino, or alluvial rocks, and vege-. 
table calcareous incrustations, resembling those which are 
daily formed in situations where solutions of carbonat of lime 
flow. 
Besides these two remarkable beds, there are found, in many 
parts of Italy, superficial strata, some of which are peculiar to 
itself, while one is common to all countries. This last is the 
ordinary alluvium of rivers; such as that of the Po and the 
Adige to the northward of the Apennines, and that of the Tiber 
to the southward. Those which are peculiar to it, are the solid 
calcareous alluvial rock, called travertino, loose tufaceous mat- 
ters of the same nature, and volcanic tufas. The plain of 
Sarteano, the Maremma of Tuscany, the Solfatara, and the. 
vicinity of Rome, offer examples of these strata. The calca- 
reous substances sometimes contain fresh-water shells and 
vegetables; nor are these always absent from the volcanic 
tufas. 
Hence arises a confusion which requires to be explained, be- 
cause it has very much obscured this subject. In his last work 
on Rome, Brocchi has cleared up some circumstances which 
he had not explained before; and it will shortly be seen that 
there is no difficulty in explaining the whole, and in simplifying 
the facts, merely by approximating and comparing them. 
The chief confusion, in this part, consisted in the transpor- 
tation of the volcanic substances, and in their cementation by 
means of the calcareous waters which flow from the Apennines. 
In consequence of this they sometimes contain matters, the 
presence of which would otherwise be unaccountable ; such as 
vegetables, and land ox river shells. In the same way they 
alternate, or are strangely and irregularly intermixed, with the 
travertino and the loose alluvia of the rivers; while they are 
also found in places far from the vicinity of recent volcanoes, 
or from even the suspicion of ancient ones. 
It is easy to’comprehend the fallacies that must have arisen 
