It is very probable that the store of cold laid up in these caves, as in an ice-house, has been ultimately derived from the great refrigeration of climate in Europe in the Glacial Period. _Conclusion._ In this chapter we have examined the physical history of caves, their formation, and their relation to pot-holes, cirques, and ravines; and we have seen that they are not the result of subterranean disturbance, but of the mechanical action of rain-water and the chemical action of carbonic acid, both operating from above. We have seen that cave-hunting is not merely an adventurous amusement, but also a quest that brings us into a great laboratory, so to speak, in which we can see the natural agents at work that have carved out the valleys and gorges, and shaped the hills wherever the calcareous rocks are to be found. The rest of this treatise will be devoted to the evidence which they offer as to the former inhabitants, both men and animals, of Europe. CHAPTER III. HISTORIC CAVES IN BRITAIN. Definition of Historic Period.--Wild Animals in Britain during the Historic Period.--Animals living under the care of Man.-- Classificatory value of Historic Animals.--The Victoria Cave, Settle, Yorkshire.--History of Discovery.--The Romano-Celtic or Brit-Welsh Stratum.--The Bones of the Animals.--Miscellaneous Articles.--The Coins.--The Jewelry, and its Relation to Irish Art.--Similar Remains in other Caves in Yorkshire.--These Caves used as Places of Refuge.--The evidence of History as to Date.--Britain under the Romans.--The Inroads of the Picts and Scots.--The English Conquest.--The Neolithic Stratum.--The approximate Date of the Neolithic Occupation.--The Grey Clays. --The Pleistocene Occupation by the Hyænas.--The probable Preglacial Age of the Pleistocene Stratum.--The Kirkhead Cave. --Poole’s Cave, near Buxton.--Thor’s Cave, near Ashbourne.-- Historic value of Brit-Welsh Group of Caves.--Principal Animals and Articles.--The use of Horse-flesh.--The Cave of Long-berry Bank. _Definition of Historic Period._ In the preceding chapter the origin of caves has been discussed, as well as their relation to the physical geography of the districts in which they are found. We must now pass on to the biological division of the subject, which relates to the animals that they contain and the inferences that may be drawn from their occurrence. The caves will be divided into historic, prehistoric, and pleistocene, according to the principles laid down in the first chapter.