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POPULAR SCIENCE REVIEW. 
of tlie kettle-shaped valleys, are further illustrations of the work 
of nature in this respect. 
The weathering of the limestones in the Ionian Islands 
affords some of the most interesting and remarkable examples 
of sub -aerial action that can anywhere be seen. It is worth 
travelling to Greece to see what can be done in this way. 
From time immemorial Greece and the Greek islands have 
been remarkable for them troublesome barking dogs, and also 
for the means nature provides for ridding oneself of the annoy- 
ance. Homer tells us that when poor Ulysses, disguised by 
Minerva, visited his old swineherd Eunmeus at the Rock of 
Corax, in Ithaca, he landed, and had no sooner approached 
the enclosure than he was attacked by his own dogs. So 
accustomed, however, are the dogs to be driven off by throwing 
at them the innumerable loose stones ever at hand, that one 
has only to stoop to ensure their running away. The history 
of these stones is not a little interesting, for they are the 
examples, proofs, and indications of destruction caused by the 
air and the weather. 
The loose stones are so predominant that it is not often one 
has an opportunity of seeing the actual solid rock beneath ; 
and in a majority of cases, w r hen compact rock is seen, it is a 
reconstructed mass or breccia of stones, either rounded or 
angular, which for some local reason has formed a capping 
and checked the atmospheric action. It is interesting to trace 
the history of destruction. Selecting a particular stone of 
large size, we shall find it pierced by numerous holes of various 
depth. Some run quite through, a passage having been bored 
whose size varies from an inch to a foot in diameter. In these 
the boring implement is no longer visible. Others are bored 
to a depth of a few inches, a foot, or even a yard. In the 
smaller bores are single plants, small or large, according to 
circumstances ; in the larger ones, a complete garden and a 
quantity of vegetable soil. I have seen at least a dozen kinds 
of wild plants at the bottom of one wide and deep hole. Nor 
are these holes all vertically downward. They slope at con- 
siderable angles. Some of them are so placed that they can 
hardly allow the rain to enter. Some are irregular ; some are 
imperfect ; but the connection of vegetation with the holes 
bored in the stone is quite unmistakeable. I have often seen 
and studied weathering in rocks of various degrees of hard- 
ness, but I know of no such examples of rapid and complete 
weathering. Riddled by these holes, which cross each other 
in various directions, the large detached rocks are rapidly 
converted into smaller ones, and these again, into mere stones. 
Ultimately, no doubt, the stones are rolled and ground down 
to powder and sand, or are carried into the valleys ; but as fast 
