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land, and the 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,

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 Val di Roppa. Entirely without natural drainage, it is the receptacle of a large quantity of rain falling on the mountain sides adjacent. All this rain runs down into the valley, carrying with it abundant stones and mud from the hill sides. These gradually 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 waterfowl. 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 surrounding 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 Val di Roppa. În Santa Maura I have seen them exactly resembling 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

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down from the hills. They are in fact valleys produced by the sinking in of the strata into some great natural cavern formed or enlarged by the infiltration of the rain-water. They vary much in size, but none are too large to be thus explained.

As might be expected, caverns abound in districts so calcareous, and many of them have been described. They offer nothing remarkable, except indeed that in the island of Cerigo, which does not belong naturally to the Ionian group, the limestone fragments have formed a breccia with bones of extinct animals; but all of them illustrate the state of the rock. There is, however, a still more curious illustration of this in Cephalonia, close to the town of Argostoli. A large and broad gulf enters from the south to the western part of Cephalonia, and from this a small transverse bay opens to the east. A spit of comparatively low ground with hills behind marks the junction of these two bays. Part of the land here appears to have sunk in, and the naked limestone rock, much broken, forms a kind of reef, keeping the sea from the narrow low tract of sunken ground. At three or four places the reef is broken, and the sea enters narrow irregular fractures, and is swallowed up in the earth. Advantage has been taken of this curious inversion of the usual order of things, and two mills are worked by the power of the entering stream of salt water made to turn an undershot wheel. The mills worked by the rush of sea-water losing itself in the earth have long been a subject of great astonishment both to the inhabitants and to the few strangers who visit Argostoli. Certainly, that there should thus be a permanent rush of water into cavities in the rocks close to the sea, and considerably below the sealevel, and that this should go on permanently, or for an indefinite period, without filling the cavern, is an extraordinary phenomenon, and requires explanation. No doubt, the generally broken and cavernous state of the limestone, in all directions, suggests a clue to the mystery; but the full explanation is to be found in the climate, which is such that, during a great part of the year, the surface is always burnt up, so that the evaporation must exceed the natural supply from rain if any means exists of supplying the deficiency. The rock being split, and full of capillary fissures as well as more open cracks, there will always be evaporation from the pools or moist rock at whatever depth, so long as the surface is dry and heated. Thus, the water entering the broken rock finds its level in some subterranean caverns where the surface always remains below that of the sea, because more water is carried off by evaporation than is received from the sea and the rains together. The perfect dryness of the surface, combined with the presence of malaria in the Val di Roppa, and many others of the 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-aërial 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 their troublesome barking dogs, and also for the means nature provides for ridding oneself of the annoyance. Homer tells us that when poor Ulysses, disguised by Minerva, visited his old swineherd Eumæus 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, when 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 considerable 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 aş fast

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as one broken surface is cleared off another is ready, preserving the same general appearance, though with materials constantly changing.

It was an interesting point to discover, if possible, the time required for this destruction in any particular case, and though not easy in a single observation, there are means at hand in these islands which help greatly an estimate. Such are the ancient walls of cities celebrated in history, but of which absolutely nothing now remains but vast blocks of stone piled in regular order, and originally serving as a defence against the most approved mode of attack in their day. The latest period of the most complete work of this kind is more than two thousand years ago. No doubt at that time the walls of the ancient Samos in Cephalonia, attacked by the Romans and resisting for four months the most strenuous attacks of M. Fulvius, were in good condition; and therefore, in looking at their present state, we see the work of twenty centuries, or thereabouts, of weathering. Of the buildings enclosed within the walls, some may have been built, and all, no doubt, were covered in with tiles ; for the whole soil is so mixed up with fragments of burnt clay, that the stones, however abundant, are hardly noticed. The ground is literally covered with pale red fragments of burnt clay, and as brick is less liable to injury than limestone from weathering, there is good reason for this. But although a place where stone is so infinitely abundant, and in a country whose inhabitants were certainly familiar enough with the mode of working it, so that there was every possible reason for stone having been used for all kinds of constructive purposes, hardly one fragment of stone-work has been discovered either on the surface or buried, except the walls themselves. And there is but one explanation-everything else has been worn to powder by weathering. In the ruins below, where the Romans established themselves and remained for a long time, it is curious to see how well their work has been kept when consisting of bricks and mortar, or even terra-cotta of the commonest kind; but there also, except a fragment or two of statuary sheltered amongst the ruins, there are no worked stones.

The reason why the walls still remain, in spite of the absolute annihilation of every other sculptured stone, one has not far to seek. The whole design and construction of these walls is on a scale so gigantic as to have fairly resisted the efforts of decay in many parts, while in others it has partially yielded ; and it is this partial destruction which renders the whole in some measure a scale by which to estimate the rate of decay. The walls are of the kind called Cyclopean-composed of hewn stones of size so gigantic that no one in modern times has given a satisfactory account of the mechanical means by which they could have been · lifted into their places. Like those curious Druidical monuments in Western Europe and on our own island, they contain a mystery. The construction shows three stages of rough art. The earliest involves only the selection of large blocks, whose surface was dressed, but of which the natural shape was not altered. Marvellous ingenuity was shown in so selecting and placing these stones that the salient angles of one should fit the retiring angles of others, so that a solid and compact wall should be formed without mortar. The blocks of this work vary from one to five tons in weight. The second stage involved the use of larger stones cut to regular shapes, but not with right angles. The stones are polygons, perfectly worked and accurately fitted. Some of the larger stones must weigh ten tons, and there are few smaller than two tons, even to fill up gaps. Lastly, the stones are found regularly squared, like those still used, but of dimensions utterly beyond comparison. Single stones, sixteen feet long, four or five feet high, and three or four wide, are not unknown. Large stones have been raised to a height of ten or twelve feet; and the walls themselves that surrounded the town of Samos in Cephalonia, when it was attacked by the Romans, were not less than twenty-five feet in height. It is clear that the oldest work had failed from time to time, and had been replaced here and there by new work in the style of the day; and thus the same wall will contain portions of each style down to the Roman occupation. It is certain that from the time of the Romans to the present day there have not been inhabitants in the Ionian Islands to perform the utterly useless task of removing these heavy stones for any useful or mischievous purpose. No town or even village has been built near, except a few houses in the present century. Any injury the walls have suffered must be by the hand of time. When, therefore, we see them partially standing, partly fallen-when we find the ground on each side of the walls blocked up with fragments, shapeless and weather-worn, with trunks of trees grown into and enlarging the intervals between two stones, and thus dislodging the upper ones—we may be sure that nature alone has operated. The result is that of the whole length of a great wall, originally not less than twelve feet wide and upwards of twenty feet high, there now remain only the lower stones. These are much interrupted by large gaps ; the stones that are still in their place are almost without exception pierced through and through with large holes, in which, when incomplete, plants will invariably be found. The stones most recently overthrown are now being broken up into small fragments by similar action, and in many cases the very rock itself

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