CAVE (Latin cavea), a hollow extending beneath the surface of the earth. Caves have excited the awe and wonder of mankind in all ages, and have been the centres round which have clustered many legends and superstitions. They were the abode of the sibyls and the nymphs in Roman mythology, and in Greece they were the temples of Pan, Bacchus, Pluto, and the Moon, as well as the places where the oracles were delivered at Delphi, Corinth, and Mount Cithaeron. In Persia they were connected with the obscure worship of Mithras. Their names frequently are survivals of the superstitious ideas of antiquity, as for example, the Fairy, Dragon’s, or Devil’s Caves of France and Germany. Long after the Fairies and Little Men had forsaken the forests and glens of Germany, they dwelt in their palaces deep in the Hartz Mountains, in the Dwarfholes, <kc., whence they came from time to time into the upper air.
Caves have been used in all ages by mankind for habitation, refuge, and burial. In the Old Testament we read that when Lot went up out of Zoar he dwelt in a cave with his two daughters. The five kings of the Canaanites took refuge from Joshua, and David from Saul, in the caves of Palestine, just as the Aquitani fled from Caesar to those of Auvergne, and the Arabs of Algeria to those of Dahra, where they were suffocated by Marshal Pelissier in 1845. In Central Africa Dr Livingstone tells us that there are vast caves in which whole tribes find security with their cattle and household stuff....
The cave of Machpelah may be quoted as an example of their use as sepulchres, and the rock-hewn tombs of Palestine and of Egypt, and the Catacombs of Rome probably owe their existence to the ancient practice of burial in natural hollows in the rock. We might therefore expect to find in them most important evidence as to the ancient history of mankind, which would reach long beyond written record; and since they have always been used by wild beasts as lairs we might reasonably believe also that their exploration would throw light upon the animals which have in many cases disappeared from the countries which they formerly inhabited. The labours of Buckland, Pengelly, Falconer, Lartet, and Christy, and Dawkins, carried on during the last fifty years in the caves, have added an entirely new chapter to the history of man in Europe, as well as established the changes that have taken place in the European fauna. The physical history of caves will be taken first, and we shall then pass on to the discoveries relating to man and the lower animals which have been made in them of late years.
Physical History. — The most obvious agent in hollowing out caves is the sea. The set of the currents, the force of the breakers, the grinding of the shingle inevitably discover the weak places in the cliff, and leave caves as one of the results of their work, modified in each case by the local conditions of the rock. Those formed in this manner are easily recognized from their floors being rarely much out of the horizontal; their entrances are all in the same plane, or in a succession of horizontal and parallel planes, if the land has been elevated at successive times. From their inaccessible position they have been rarely occupied by man. Among them Fingal’s Cave, on the island of Staffa, off the south-west coast of Scotland, hollowed out of columnar basalt, is 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 expansion of steam and gases in the lava while it was in a molten state. They have been observed in the regions round Vesuvius and Etna, in Iceland and Teneriffe. We may take as an example the Grotto del Cane (cave of the dog), near Pozzuoli, a few miles to the south-west of Naples, remarkable for the flow of carbonic acid from crevices in the floor, which fills the lower part of the cave and suffocates any small animal, such as a dog, immersed long enough in it.
The most important class of caves, however, and that which immediately demands our notice, is that composed of those which have been cut out of calcareous rocks by the action of carbonic acid in the rain-water, combined with the mechanical friction of the sand and stones set in motion by the streams which have, at one time or another, flowed through them. They occur at various levels, and are to be met with wherever the strata are sufficiently compact to support a roof. Those of Brixham and Torquay, and of the Eifel are in the Devonian limestone; those of Wales, Somerset, the central and northern counties of Belgium, Saxony, and Westphalia, of Maine and Anjou, of Virginia and Kentucky, are in that of the Carboniferous age. The cave of Kirkdale in Yorkshire, and most of those in Franconia and Bavaria, penetrate Jurassic limestones. The compact Neocomian and cretaceous limestones of Central France contain most of the caverns of Perigord, rendered famous by the discovery of the remains of the Eskimos along with the animals which they hunted; as well as those of Northern Italy,’ Sicily, Greece, Dalmatia, Carniola, and Palestine. The cave of Lunelviel near Montpellier is the most important of those which have been hollowed in limestones of the Tertiary age. They are also met with in rocks composed of gypsum; in Thuringia, for example, they occur in the saliferous and gypseous strata of the Zechstein, and in the gypseous Tertiary rocks of the neighbourhood of Paris, as for example at Montmorency.
Caves formed by the action of carbonic acid, and the action of water are distinguished from others by the following characters. They open on the abrupt sides of valleys and ravines at various levels, and are arranged round the main axes of erosion, just as the branches are arranged round the trunk of a tree. In a great many cases the relation of the valley to the ravine, and of the ravine to the cave, is so intimate that it is impossible to deny that all three have been produced by the same causes. The caves themselves ramify in the same irregular fashion as the valleys, and are to be viewed merely as the capillaries in the general valley system through which the rain passes to join the main channels. Sometimes, as in the famous caves of Adelsberg, Kentucky, Wookey Hole in Somersetshire, the Peak in Derbyshire, and in many in the Jura, they are still the passages of subterranean streams; but very frequently the drainage has found an outlet at a lower level, and the ancient watercourses have been deserted. These in every case present unmistakable proof that they have been traversed by water in the sand, gravel, and clay which they contain, as well as in the worn surfaces of the sides and bottom. In all districts where there are caves there are funnel-shaped depressions of various sizes called pot-holes or swallow-holes, or bêtoires, “chaldrons du diable,” “marmites des géants,” or “kata-vathra,” in which the rain is collected before it disappears into the subterranean passages. They are to be seen in all stages, some being mere hollows which only contain water after excessive rain, while others are profound vertical shafts into which the water is continually falling. That known as Helln Pot in Yorkshire, 300 feet deep, is an example of the latter class. The cirques described by Μ. Desnoyers belong to the same class as the swallow-holes.
The history of swallow-holes, caves, ravines, and valleys in calcareous strata may be summed up as follows. The calcareous rocks are invariably traversed by joints or lines of shrinkage, which are lines of weakness by which the direction of the drainage is determined; and they are composed to a large extent of carbonate of lime, which is readily exchanged into soluble bicarbonate by the addition of carbonic acid. The rain in its passage through the air takes up carbonic acid, and it is still further charged with it in percolating through the surface soil in which there is decomposing vegetable matter. As the rain drops converge towards some one point, determined by some local accident on the surface, and always in a line of joint, the carbonic acid attacks the carbonate of lime with which it comes into contact, and thus a funnel is gradually formed ending in the vertical joint below. Both funnel and vertical joint below are being continually enlarged by this process. This chemical action goes on until the free carbonic acid is used up. The subterranean passages are enlarged in this manner, and what was originally an insignificant net-work of fissures is developed into a series of halls, sometimes as much as from 80 to 100 feet high. These results are considerably furthered by the mechanical friction of the pebbles and sand hurried along by the current, and by falls of rock from the roof produced by the removal of the underlying strata. In many cases the results of this action have produced a regular subterranean river system. The thick limestones of Kentucky, for example, are traversed by subterranean waters which collect in large rivers, and ultimately appear at the surface in full power. The River Axe, near Wells, the stream flowing out of the Peak Cavern at Castleton, Derbyshire, that at Adelsberg (see Adelsberg, vol. i. p. 151) in Carniola, flow out of caverns in full volume. The River Styx and the waters of Acheron disappear in a series of caverns which were supposed to lead down to the infernal regions.
If the direction of the drainage in the rock has been altered, either by elevations such as those with which the geologist is familiar, or by the opening out of new passages at a lower level, these watercourses become dry, and present us with the caves which have afforded shelter to man and the wild animals from the remotest ages, sometimes high up on the side of a ravine, at other times close to the level of the stream at the bottom.
Caves, as a general rule, are as little effected by disturbances of the rock as the ravines and valleys, which have been formed, in the main, irrespective of the lines of fault or dislocation.
We must now examine what happens to the bicarbonate of lime which has been formed by the action of the acid on the limestone. If a current of air play upon the surface of the water, the carbonic acid, which floats up the lime, so to speak, is given off and the insoluble carbonate is deposited, and as a result of this action we have the elaborate and fantastic stony incrustations termed stalactites and stalagmites. The water percolating through the rock covers the sides of the cavern with a stalactitic drapery, and if a line of drops persistently falls from the same point to the floor, the calcareous deposit gradually descends from the roof, forming in some cases stony tassels, and in others long columns which are ultimately united to the calcareous boss, formed by the plash of the water on the floor. The surface also of the pools is sometimes covered over with an ice-like sheet of stalagmite, which shoots from the sides, and sometimes forms a solid and firm floor when the water on which it was supported has disappeared. Sometimes the drops form a little calcareous basin, beautifully polished inside, which contains small pearl-like particles of carbonate of lime, polished by friction one against the other. The most beautiful stalactitic caves in Great Britain are those of Cheddar in Somerset, Caldy Island, and Poole’s Cavern at Buxton. A portion only of the carbonate of lime is thus deposited in the hollows of the rock from which it was taken; the rest is carried into the open air by the streams, in part deposited on the sides and bottom, forming tufa and the so-called petrifactions, and partly being conveyed down to the sea to be ultimately secreted in the tissues of the Mollusca, Echinodermata, and Foraminifera. Through these it is again collected in a solid form, and in the long course of ages it is again lifted up above the level of the water as limestone rock, and again undergoes the same series of changes. Thus the cycle of carbonate of lime is a never-ending one from the land to the ocean, from the ocean to the land, and so it has been ever since the first stratum of limestone was formed out of the exuviae of the inhabitants of the sea. The rate of the accumulation of stalagmite in caverns is necessarily variable, since it is determined by the presence of varying currents of air. In the Inglebor∩ugh cavern a stalagmite, measured in 1839 and in 1873, is growing at the rate of ’ 2946 inches per annum. It is obvious, therefore, that the vast antiquity of deposits containing remains of man underneath layers of stalagmite cannot be inferred from a thickness of a few inches or even of a few feet.
The intimate relation which exists between caves and ravines renders it extremely probable that many of the latter have been originally subterranean watercourses, which have been unroofed by the degradation of the rock. In all limestone districts ravines are to be found continued in the same direction as the caves, and the process of atmospheric erosion may be seen in the fallen blocks of stone which generally are to be met with at the mouths of the caverns. In illustration of this the valley and caves of Weather-cote, in Yorkshire, may be quoted, or the source of the Axe at Wookey; and the ravine formed in this way has very frequently been widened out into a valley by the action of subaerial waste, or by the grinding of glaciers through it during the glacial stage of the Pleistocene period.
Pleistocene Caves in Europe. — The caves which have offered shelter to man and the wild animals are classified according to their contents. 1⅛i, Those containing the extinct animals, such as the mammoth, woolly rhinoceros, or Palaeolithic man (see Archaeology), are termed Pleistocene. These are sometimes called Quaternary, under the mistaken idea that they belong to an age succeeding the Tertiary period. 2d, Those which contain the remains of the domestic animals in association with the remains of man either in the Neolithic, Bronze, or Iron stages of civilization are termed Prehistoric. 3√, The third group consists of those which can be brought into relation with the historic period, and are therefore termed Historic.
The search after ebur fossile or unicorns’ horn, or in other words the fossil bones which ranked high in the materia medica of the 16th and 17th centuries, led to the discovery of the ossiferous caverns of the Hartz Mountains, and of Hungary and Franconia. The famous cave of Gailenreuth in the last of these districts was explored by Dr Goldfuss in 1810. The bones of the hyaena, lion, wolf, fox, and stag, which it contained, were identified by Baron Cuvier, and some of the skulls have been recently proved by Professor Busk to belong to the grizzly bear. They were associated with the bones of the reindeer, horse, and bison, as well as with those of the great cave bear. These discoveries were of very great interest, because they established the fact that the above animals had lived in Germany in ancient times. The first bone cave systematically explored in England was one at Orreston near Plymouth in the year 1816, which proved that an extinct species of rhinoceros (R. Megarhinus) lived in that district. Four years later the famous hyaena den at Kirkdale in Yorkshire was explored by Dr Buckland. He brought forward proof that it had been inhabited by hyaenas, and that the broken and gnawed bones of the mammoth, rhinoceros, stag, bison, and horse belonged to animals which had been dragged in for food. He pointed out that all these animals had lived in Yorkshire in ancient times, and that it was impossible for the carcases of the rhinoceros, hyaena, and mammoth to have been floated from tropical regions into the places where he found their bones. He subsequently investigated bone caves in Derbyshire, South Wales, and Somerset, as well as in Germany, and published his Religuiae Diluvianae in 1822, a work which laid the foundations of the new science of cave-hunting in this country. The well-known cave of Kent’s Hole near Torquay, furnished the Rev. J. McEnery, between the years 1825 and 1841, with the first flint implements discovered in intimate association with the bones of extinct animals. He recognized the fact that they proved the existence of man in Devonshire while those animals were alive, but the idea was too novel to be accepted by his contemporaries. His discoveries have since been verified by the subsequent investigations carried on by Mr Godwin Austen, and ultimately by the committee of the British Association, which has been at work for several years under the guidance of Mr Pengelly. There are four distinct strata in the cave. 1sZ, The surface is composed of dark earth, and contains mediaeval remains, Roman pottery, and articles which prove that it was in use during the Iron, Bronze, and Neolithic ages. 2d, Below this is a stalagmite floor, varying in thickness from 1 to 3 feet, and covering (3cZ) the red earth, which contained bones of the hyaena, lion, mammoth, rhinoceros, and other animals, in association with flint implements and an engraved antler, which proved man to have been an inhabitant of the cavem during the time of its deposition. ⅛th, Filling the bottom of the cave is a hard breccia, with the remains of bears and flint implements, in the main ruder than those found above; in some places it was no less than 12 feet thick. The most remarkable animal found in Kent’s Hole is the sabre-toothed carnivore, Mackairodus latidens of Owen. While the value of Mr McEnery’s discoveries was in dispute the exploration of the cave of Brixham near Torquay in 1858 proved that man was coeval with the extinct mammalia, and in the following year additional proof was offered by the implements that were found in Wookey Hole. Similar remains have been met with in the caves of Wales, and in England as far north as Derbyshire (Creswell), proving that over the whole of southern and middle England men, in precisely the same stage of rude civilization, hunted the mammoth and rhinoceros and other extinct animals.
Cave-dwellers allied to Eskimos. — The caves and rock shelters of Perigord, explored by the late Μ. Lartet and our countryman Mr Christy, in 1863-4, have not only afforded accumulative proof of the co-existence of man with the extinct mammalia, but have given us a clue as to the race that so existed. They penetrate the sides of the valleys of the Dordogne and Vezère, and offer as vivid a picture of the life of the period as that revealed of Italian manners in the 1st century by the buried cities of Herculaneum and Pompeii. The old floors of human occupation consist of broken bones of animals killed in the chase, mingled with rude implements and weapons of bone and unpolished stone, and with charcoal and burnt stones, which indicate the position of the hearths. Flakes without number, awls, lance-heads, hammers, and saws made of flint rest pele-mele with bone needles, sculptured reindeer antlers, arrowheads, and harpoons, and bones of the reindeer, bison, horse, ibex, Saiga antelope, and musk sheep. These singular accumulations of debris mark the places where the ancient hunters lived, and are merely the refuse cast aside. The reindeer formed by far the greater portion of the food, and must have lived in enormous herds at that time in the centre of France. From this, as well as from the presence of the most arctic of the herbivores, the musk sheep, we may infer the severe climate of that portion of France at that time. Besides these animals the cave bear and lion have been met with in one, and the mammoth in five localities, and their remains bear marks of cutting or scraping which showed they fell, a prey to the hunters. The most remarkable remains left behind in these refuse heaps are the sculptured reindeer antlers and figures engraved on fragments of schist and on ivory. A well-defined outline of an ox stands out boldly from one piece of antler; a second represents a reindeer kneeling...
