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POPULAR SCIENCE REVIEW. 
land, and tlie ridge continues to the sea on both sides. It is 
on the south side of this chain that the enclosed valleys are 
seen that are so characteristic of the islands. 
There is a very beautiful ride or drive from Corfu across 
the island to Pelleka, a cliff overlooking towards the west a 
lovely broken piece of wooded but little cultivated ground, 
not unlike some part of the Undercliff of the Isle of Wight. 
Looking east, the rich plains of Corfu are seen dotted here 
and there with small villages. To the north, however, the 
view is very different. Coming to the very edge of an inland 
cliff, one sees with astonishment a tract immediately below 
extending at a perfectly dead level for some miles, shut in 
towards the north by the mountain range of San Salvador, 
which rises with singular abruptness ; shut in also on each side 
by other lower hills, but equally abrupt. Towards the west 
the hills are very narrow, merely serving to separate the valley 
from the sea. This remarkable valley is called the Yal di 
Poppa. Entirely without natural drainage, it is the receptacle 
of a large quantity of rain falling on the mountain sides adja- 
cent. All this rain runs down into the valley, carrying with 
it abundant stones and mud from the hill sides. These gra- 
dually accumulate, and have formed the flat bottom. The rain, 
retained for some months on this bottom, poisons the air of the 
whole neighbourhood, but is generally evaporated off in time to 
allow of crops being sown. During winter it is first a lake, 
and then a swamp, and is a favourite place for shooting - water- 
fowl. During spring it is cultivated. During summer it is the 
source of malaria, and helps, no doubt, to render the air of 
Corfu so insalubrious, that the population for many years past 
has been almost stationary, and the miserable villages sur- 
rounding the valley are kept constantly at the lowest point ; the 
men and. women dying young, and the children being seldom 
reared. 
This valley is only one of several. Immediately adjacent is 
another of the same kind. Not far off is another perfectly 
round, where the water remains so long on the ground that 
there is no cultivation. South of Santi Deca, in the other part 
of the island, there is one known as the lake of Corissia, shut 
in in a nearly similar manner, and almost as large as the Yal 
di Poppa. In Santa Maura I have seen them exactly resem- 
bling a vast artificial amphitheatre. In Cephalonia they are 
deep lakes. Wherever they are seen they are of a similar 
nature. They are great hollows with limestone bottoms, sur- 
rounded by limestone rocks. From the rate at which the 
water disappears through the bottom, it is certain that they have 
communication with some natural drainage, only checked by 
the deposit forming at the surface by what the rain brings 
