PHYSICAL GEOGRAPHY OP THE IONIAN ISLANDS. 
55 
metamorphic limestones may all be found. Mineral veins, 
however, in the limestone are not common, and lead and zinc 
ores, common in cases where the. limestone is less pure, are 
not known in the district. Sulphur is the only important 
mineral hitherto discovered, and this is not in veins, but either 
bedded or nodular. Caverns are common ; but no very large 
ones have been described, except in Cerigo. In the other 
islands they are small, and have been traced only to a short 
distance, owing probably to the tenderness of the limestone, 
which falls in before very large open spaces have had time to 
form. What is wanted in extent is doubtless made up in 
number, and it is certain that the rock is everywhere much 
fissured, and freely open to the passage of water. 
The islands are unquestionably more interesting in their 
physical geography than in their geology, and most of the 
points of geology have already been alluded to as related to 
existing operations of nature. Of fossils, few have been 
found, and these possess no great interest. Perhaps some day 
a careful examination of the contents of the Cerigo caverns 
may throw light on the great question of the existence of 
human beings in Europe together with the large extinct quad- 
rupeds; but there is no evidence yet. The hipperite limestone 
of Cephalonia is fossiliferous, but has not produced anything 
new. The tertiary limestones and marls near Argostoli, also 
in Cephalonia, have been found rich in specimens, and are 
worth more careful working than they have yet received. 
