Southern Europe.—In southern Europe the bone-caves of Sicily, worked in 1829 for the sake of the animal remains to be used in sugar refining, were scientifically examined by Dr. Falconer in 1859; those of Malta by Captain Spratt in the same year; and those of Gibraltar by Captain Broome in the years 1862–8. They established the existence of the serval and the African elephant, and other characteristic African species, in Europe, and offer as we shall see in this work, important testimony as to the geography of the Mediterranean area in the Pleistocene age.
In this outline of the history of cave-exploration it will be seen, that the additions to our knowledge of the past have been neither few nor insignificant, nor in one line of inquiry. And if the attention which is now being directed to the subject be due to the general development of scientific thought, it is equally true, that the results have reacted on scientific thought in general, and have especially benefited the sciences of geology, archæology, and history. A rich field of investigation lies before the cave-hunter, in Greece, Palestine, Lycia, Persia, and the limestone plateaux of central Asia; and since these discoveries have been so valuable in central and north-western Europe, what may we not recover from the grasp of oblivion, of the infancy and early culture of mankind in the very birth-place and “pathway of the nations”?
CHAPTER II.
PHYSICAL HISTORY OF CAVES.
Caves formed by the Sea and by Volcanic Action.—Caves in Arenaceous Rocks.—Caves in Calcareous Rocks of various ages.—Their Relation to Pot-holes, “Cirques,” and Ravines.—The Water-cave of Wookey Hole.—The Goatchurch Cave.—The Water-caves of Derbyshire.—Of Yorkshire.—The Ingleborough Cave.—The Rate of Deposit of Stalagmite.—The Descent into Helln Pot.—The Caves and Pots round Weathercote.—The Formation of Caves, Pot-holes, and Ravines.—Caverns not generally formed in line of Faults.—Of various Ages.—Their Filling-up.—The Cave of Caldy.—The Blackrock Cave.—Great quantity of Carbonate of Lime dissolved by Atmospheric Water.—The Circulation of Carbonate of Lime.—The Temperature of Caves.—Conclusion.
Caves formed by the Sea and by Volcanic Action.
In this chapter we shall treat of the origin of caves and of their place in physical geography. The most obvious agent in hollowing out caves is the sea. The set of the current, the tremendous force of the breakers, and the grinding of the shingle, inevitably discover the weak places in the cliff, and leave caves as the results of their work, modified in each case by the local conditions of the rock. Caves formed in this manner have certain characters which are easily recognized. Their floors are very rarely much out of the horizontal, their outlook is over the sea, and they very seldom penetrate far into the cliff. A general parallelism is also to be observed in a group in the same district, and their entrances are all in the same horizontal plane, or in a succession of horizontal and parallel planes. In some cases they are elevated above the present reach of the waves, and mark the line at which the sea formerly stood. From their generally inaccessible position sea-caves have very rarely been occupied by man, and the history of their formation is so obvious that it requires no further notice. Among them the famous Fingal’s Cave, off the north coast of Ireland, and that of Staffa, on the opposite shore of Scotland, hollowed out of columnar basalt, are perhaps the most remarkable in Europe.
In volcanic regions also there are caves formed by the passage of lava to the surface of the ground, or by the imprisoned steam and gases in the lava while it was in a molten state: but these are of comparatively little importance so far as relates to the general question of caves, from the very small areas which are occupied by active volcanoes in Europe. They have been observed in Vesuvius, Etna, Iceland, and Teneriffe.