The most important argument in favour of the pre-glacial age of the mammaliferous cave-earth is afforded by the range of the animals in Great Britain during the time that certain areas were occupied by glaciers. In a paper read before the Geological Society in 1869, I showed that those areas in Great Britain in which the marks of glaciers were the freshest and most abundant coincided with those which were barren of the remains of the pleistocene mammalia, and I therefore inferred that this was due to the fact, that the areas in question were covered by ice at the time that pleistocene animals were so numerous in the caves, and river-deposits of southern and eastern England, and on the continent. In a map published in 1871, Cumberland, Westmoreland, Lancashire, and the greater portion of Yorkshire are represented as being one of these barren areas, in which no pleistocene mammalia have been observed. It is obvious that the hyænas, bears, mammoths, and other creatures found in the pleistocene stratum, could not have occupied the district when it was covered by ice; and had they lived soon after the retreat of the ice-sheet, their remains would occur in the river-gravels, from which they are absent throughout a large area to the north of a line drawn between Chester and York, whilst they occur abundantly in the glacial river deposits south of that line. On the other hand, they belong to a fauna, that overran Europe, and must have occupied this very region before the glacial period, since their remains have been found in pre-glacial strata to the north in Scotland, to the south at Selsea, and to the east in Norfolk and Suffolk. It may, therefore, reasonably be concluded that they occupied the cave in pre-glacial times, and that the stratum in which their remains lie buried, was protected from the grinding of the ice-sheet, which destroyed nearly all the surface accumulations in the river-valleys, by the walls and roof of rock, which has since, to a great extent, been weathered away.[76] This view is also held by Mr. Tiddeman. The exploration of the Victoria Cave, which has hitherto yielded such interesting evidence of three distinct occupations--first by hyænas, then by neolithic men, and lastly by the Brit-Welsh, is by no means complete. The cave itself is of unknown depth and extent, and the mere removal of so much earth and clay as it is at present known to contain will be a labour of years. The results of the exploration, up to the present time, are of almost equal value to the archæologist, to the historian, and the geologist, and prove how close is the bond of union between three branches of human thought which at first sight appear remote from each other. The discussion of the problems connected with the neolithic and pleistocene strata must be referred to the fifth and following chapters. _The Kirkhead Cave._