276 Dr. Mac Culloch on the 
more recent date. At the same time, instead of being driven 
to seek for causes by a circuitous and analogical road, we find 
these at hand in the general volcanic nature of the country 
under review, while, in some places, we can almost trace the 
very cause itself in action. 
In different places, and in Italy very particularly, it has been 
observed, that the relative level of the sea and land is subject 
to change, and that it has in past times undergone frequent 
alterations. For the proofs and nature of these, I must refer 
to Breislak and others, who have examined this subject with 
considerable care, as I dare not prolong this paper by repeating 
them. The present case may be considered as an extreme one 
of that nature; in consequence of which the bottom of the 
sea, together with its unconsolidated alluvia has been raised 
above the surface of the water, so as to have become dry land. Thus 
it is easy to account for the presence of marine remains, as well 
as for their presence in that singularly undisturbed state which 
has been described. 
It is equally easy to account for the proximity of the marine 
and the terrestrial remains, as also for that of the alluvia which 
respectively enclose each. Whatever cause or causes generated 
the usual terrestrial alluvia that occur all over the world, these 
have apparently been deposited, in most cases, on naked rock. 
In this particular one, they have settled on a previous alluvium 
of a different character, and, as far as our present imperfect 
observations go, solitary. The apparent interference of the two 
classes of organic remains follows of course. 
If that interference is ever greater, so as'‘to amount to a real 
mixture or alternation, I have already shewn how it can be ex- 
plained, by a variety of circumstances, consisting in more recent 
changes and deposits, and in the imperfection of observations, 
the real bearings and value of which were not anticipated. But 
it is proper also to say here, that other causes of a more general 
nature may have produced the same effects without in any de- 
gree vitiating the theory here offered. 
It is believed that many of the terrestrial alluvia have been 
the produce of diluvian currents; and it is impossible, if this 
