302 ON THE ICTIS OF DIODORUS SICULUS. 
that the Ictis of Diodorus is either the Isle of 
Wight, or St. Michael’s Mount, let us proceed 
to inquire, to what causes of change the coast of 
Cornwall has been exposed, and what has been 
the actual, or the probable effect of these causes, 
operating through a long series of ages. 
The effects of oceanic agency, in bringing 
about geological changes, are of two kinds. Some- 
times the ocean forms accumulations of detritus, 
which act as barriers against its own encroach- 
ments. At other times, it obliterates all traces 
of what once was solid land; either gradually 
and slowly undermining it, or battering it down 
by a succession of attacks, or sweeping it away 
by a single mighty and resistless effort. As 
Diodorus, therefore, mentions a certain island, 
which he calls Jctis, situated near a certain pro- 
montory, which he calls Belerium ; and as Ictis, 
and the neighbouring islands, were such only at 
high water, and presented the appearance of 
peninsulas at the ebbing of the tide; it may be 
worth our while to inquire, whether they have 
lost their insular character, by an accumulation of 
detritus, or whether they are wholly, or in part, 
submerged, and their communication with the 
main land, or with each other, broken off by the 
inroads of the sea. 
