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Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 8 "Germany" to "Gibson, William"

Fossil Contents of the Genista Cave

age. Professors A. C. Ramsay

and James Geikie (_Quarterly Journal of the Geological Society_, London, August 1878) found also in the superficial formations of the Rock various features of interest to the students of Pleistocene geology, including massive accumulations of limestone breccia or agglomerate, bone breccias, deposits of calcareous sandstone, raised beaches and loose sands. The oldest of these superficial formations is the limestone breccia of Buena Vista, devoid of fossils and apparently formed under the stress of hard frosts, indicating conditions of climate of great severity. To account for frosts like these, it is suggested that the surface of the Rock must have been raised to an elevation much greater than its present height. In that case Europe and Africa would probably have been connected by an isthmus across some part of the present site of the Straits, and there would have been a wider area of low ground round the base of the Rock. The low ground at this, and probably at a later period, must have been clothed with a rich vegetation, necessary for the support of a varied mammalian fauna, whose remains have been found in the Genista caves. After this there would seem to have been a subsidence to a depth of some 700 ft. below the existing level. This would account for the ledges and platforms which have been formed by erosion of the sea high above the present sea-level, and for the deposits of calcareous sandstone containing sea shells of existing
Mediterranean species. The extent of some of these eroded ledges shows that pauses of long duration intervened between the periods of depression. The Rock seems after this to have been raised to a level considerably above that at which it now stands; Europe and Africa would then again have been united. At a later date still the Rock sank once more to its present level.

Many caves, some of them of great extent, penetrate the interior of the rock; the best known of these are the Genista and St Michael's caves. St Michael's cave, about 1100 ft. above sea-level at its mouth, slopes rapidly down and extends over 400 ft. into the Rock; its extreme limits have not, however, been fully explored. It consists of a series of five or more chambers of considerable extent, connected by narrow and crooked passages. The outermost cave is 70 ft. in height and 200 in length, with massive pillars of stalactite reaching from roof to floor. The second cave was named the Victoria cave by its discoverer Captain Brome; beyond these are three caves known as the Leonora caves. "Nothing," writes Captain Brome, "can exceed the beauty of the stalactites; they form clusters of every imaginable shape--statuettes, pillars, foliages, figures," and he adds that American visitors have admitted that even the Mammoth cave itself could not rival these giant stalactites in picturesque beauty.

The mammalian remains of the Genista cave have been described by G. Busk ("Quaternary Fauna of Gibraltar" in _Trans. of Zool. Soc._ vol. x. p. 2, 1877). They were found to contain remains of a bear, probably _Ursus fossilis_ of Goldfuss; of a hyena, _H. crocuta_ or _spelaea_; of cats varying from a leopard to a wild cat in size; of a rhinoceros, resembling in species remains found in the Thames valley; two forms of ibex; the hare and rabbit. No trace has been found as yet of _Rhinoceros tichorinus_, of _Ursus spelaeus_ or of the reindeer; and of the elephant only a molar tooth of _Elephas antiquus_.

Further details may be found in the _Quarterly Journ. of Geol. Soc._ (James Smith of Jordanhill), vol. ii. and in vol. xxi. (_Fossil Contents of the Genista Cave_, G. Busk and Hugh Falconer; reprinted in _Palaeontological Memoirs_, H. Falconer, London, 1868).

_Flora._--The upper part of the Rock is in summer burnt up and brown, but after the first autumn rains and during the winter, spring and early summer, it abounds in wild flowers and shrubs. In the public and other gardens on the lower ground, where there is a greater depth of soil, the vegetation is luxuriant and is only limited by the supply of water available for summer irrigation. Dr E. F. Kelaart (_Flora Calpensis_, London, 1846) enumerates more than four hundred varieties of plants and ferns indigenous to Gibraltar, and about fifty more which have been introduced from abroad. Of the former a few are said to be species peculiar to the Rock. The stone-pine and wild-olive are perhaps the only trees found growing in a natural state. In the public and private gardens and by the roadside may be seen the pepper tree, the plane, the white poplar, the acacia, the bella-sombra (_Phytolacca dioica_), the eucalyptus or blue gum tree, and palms of different species; and, of fruit trees, the orange, lemon, fig, pomegranate, loquat and almond. The aloe, flowering aloe and prickly pear are common, and on the eastern side of the Rock the palmito or dwarf palm (_Chamaerops humilis_) is abundant.

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