If these valley deposits be compared with the contents of some of the bone caves, such, for example, as those of the Victoria Cave (compare Figs. 74 and 75 with Figs. 20, 21, 29), it will be seen that they present the same section. The pleistocene gravels and brick-earths of the one correspond with the lower strata of the other, and contain the same extinct animals. The prehistoric alluvium of the one is represented by the layer containing neolithic bronze or iron implements, as well as the same animals; while the historic strata are represented in both by the superficial accumulations. The only difference indeed between the one and the other is, that in the former the strata of the three periods are spread over a wide area, while in the latter they are super-imposed in vertical order, the pleistocene below, the prehistoric in the middle, and the historic on the surface. _Difference in Mineral Condition of Deposits in Caves._ The prehistoric, and the historic strata in caves differ from the pleistocene in their physical constitution. They are darker in colour, and more loosely stratified, and contain bones in a more friable and less mineralized condition, and are more free from stalagmite. _The Caves of Germany: Gailenreuth._ The use of fossil bones for medicinal purposes led, as I have already mentioned in the first chapter, to the exploration of caves, which were first scientifically examined in Germany towards the close of the eighteenth century. They abound in all the limestone plateaux, especially in the region of Franconia, and in that of the Hartz. Among them the most interesting, perhaps, is that of Gailenreuth, explored by Esper, Rosenmüller, Goldfuss, Buckland, Lord Enniskillen, and Sir Philip Egerton. It penetrates a lofty cliff, that forms a side of the deep gorge which the river Weissent has cut in the rock, at a point about three hundred feet above the water level. The entrance, Dr. Buckland[177] writes, is about seven feet high and twelve feet broad, and within it a short passage leads into two chambers (Fig. 76, A and B),[178] hung with stalactites, and with the floors covered by a dense stalagmitic pavement, that has been more or less broken up by repeated diggings. These floors are perfectly horizontal, the level of that of B being considerably below that of A. They rest on an accumulation of reddish grey loam, containing pebbles, and angular limestone blocks, and vast quantities of the bones and teeth of the animals formerly living in the district. The depth of this ossiferous deposit has not been ascertained, but in the further end of the chamber B, it has been proved to be more than twenty-five feet thick. [Illustration: FIG. 76.--Section of Gailenreuth Cave. (Buckland.)]