PHYSICAL GEOGRAPHY OP THE IONIAN ISLANDS. 
465 
on which the stones were placed, as on a firm foundation, is 
lower by several feet at a little distance from the walls, these 
having sheltered the foundations while the work went on 
rapidly on the stones above. It is only in a few places that 
the height of the ancient wall is indicated. Not in a single 
instance did I see a good specimen either of Cyclopean, poly- 
gonal, or the more finished Hellenic work detached from the 
wall by accident and at all recognizable. On the other hand, 
where, as in Santa Maura, the walls have been taken down, 
and the stones removed for any purpose, the weathering has 
not affected them beyond what is due to the time they have 
been exposed. Every stone that had been removed, or fallen by 
the progress of decay, had been entirely broken up. 
Weathering on so grand a scale, and limited in this way to 
a period of time absolutely definite, is very rarely to be seen, 
and I have thought it worth while to dwell at some detail on 
the facts and inferences. It is one of the most interesting 
points in the physical geography of the Ionian Islands, and 
one of the most instructive examples of a great natural opera- 
tion everywhere going on, that has ever fallen under my 
observation. 
There are not wanting peculiarities of climate and other 
local causes that help to account for these phenomena. The 
nature of the limestone itself is also very favourable, the rock 
being in that semi-crystalline state indicative of considerable 
purity, and peculiarly liable to an infinite multitude of minute 
crevices opening a way for and even inviting the action of 
water. The water that falls from the air in the shape of rain 
is always able to effect a lodgment in such rock ; vegetable 
matter of one kind or other soon attaches itself, and the 
decay of this earliest vegetation is sure to contain the 
material for converting the oxidized water from the clouds 
into an acid solution acting rapidly on the stone. Thus each 
successive stage facilitates and hastens the operation. The 
climate being insular ensures a certain supply of rain at in- 
tervals through the year, and no doubt helps to advance the 
work. When there is room for the intrusion of the roots of 
a larger kind of vegetation than that which penetrates the 
surface, it is extraordinary to see how the natural expansion 
during growth is capable of lifting out of their places even the 
heaviest stones, and even occasionally building such stones 
into the very trunk of the tree. I have noticed this especially 
with regard to olive-trees in Santa Maura. 
