46 
POPULAR SCIENCE REVIEW. 
But if the rainfall in the Ionian Islands is, as we have reason 
to suppose, rather large in proportion to that of the adjacent 
countries, and the natural channels for carrying off the water 
to the sea are so small and few, it becomes an interesting and 
important question to consider the cause of conditions so ano- 
malous. This has already been alluded to in speaking of the 
highly- cavernous state of the limestone. Just as in various 
parts of the Mendips there are swallow holes in which the 
streams of the neighbourhood are swallowed up and made to 
disappear, so in almost every valley of all the Ionian Islands 
there is something of the same kind. In the Mendips, indeed, 
these swallowed-up rivers reappear in springs at the foot of 
the cliff in the valley below, and form streams once more, 
whereas in the Ionian Islands they are altogether lost sight of, 
the water being all carried away by evaporation from the 
general surface of the country during the long and fierce heats 
of summer. This difference, however, is one of little import- 
ance, and does not diminish the value of the explanation. All 
the rain sinks into the earth and is dispersed far and wide 
during the wet season, and during droughts the water is brought 
again to the surface by evaporation. Thus, in spite of great 
dryness and no soil, there is a cultivation of the vine in some 
places among the bare stones lying upon the naked limestone 
rock. 
The removal of forests whjch at one time seem to have 
covered large tracts of country in several of the islands has 
probably produced much effect on the general climate, but 
especially on the rainfall, and on the distribution of the rain 
after it has fallen. The trees were, for the most part, evergreen 
oaks or pines, preventing, or at least greatly checking, evapo- 
ration during summer, and acting, as trees always seem to do, 
in increasing the rainfall in the rainy season, and increasing 
the total number of days on which rain falls* It would seem 
that the very large human population formerly living on the 
islands existed at a time when these forests had not been 
removed ; and it is very possible that a tree vegetation, of slow 
growth, and of which the leaves do not fall till spring, may be 
far less injurious in malarious districts than a surface generally 
bare, but covered very quickly after the winter and early spring 
rains with a luxurious growth which again dies away and is 
burnt by the hot summer sun. Certain it is that the climate, 
in many parts of all the islands, except perhaps Ithaca, is now 
eminently malarious, and that the population increases very 
much less rapidly than should be the case in a well-governed 
country with no political drawbacks. 
In all the islands there is some kind of wet season, com- 
mencing in November and lasting at intervals till April. About 
