The beauty of the interiors of some of the caves could not fail to give rise to more graceful fancies than these. The fantastic shapes of the dripstone, with which they are adorned, now resembling Gothic pillars supporting a crystalline arcade, or jutting out in little spires and minarets, and very generally covering the floor with a marble-like pavement, and in some cases lining the pools of water with a fretwork of crystals that shine like the facets of a diamond, were fitting ornaments for the houses of unearthly beings, such as fairies. _The Physical Division of the Subject._ It is by no means my intention in this work to give a history of legends such as these, but to take my readers with me into some of the more important and more beautiful caves in this country. The exploration of the chambers and passages of which they are composed, the fording of the subterranean streams by which they are frequently traversed, or the descent into deep chasms which open in their floors, have the peculiar charm of mountaineering, not without a certain pleasurable amount of risk. But to physicist and geologist they offer far more than this. They give an insight into the wonderful chemistry by which changes are being wrought, at the present time, in the solid rock. Nor are the conclusions to which we are led by the investigation of these chemical changes merely confined to the interior of caves. They enable us to understand how some of the most beautiful scenery in Europe has been formed, and to realize the mode by which all precipices and gorges have been carved out of the calcareous rock. In the next chapter we shall see why it is that the combination of hill and valley, ravine and precipice, present the same general features in all limestone districts--why, for instance, the ravines of Palestine are the same as those of Greece, and both are identical with those in Yorkshire. The origin and the history of caves will be examined, as well as their relation to the general physical geography of the calcareous strata. All these subjects are comprehended in the first or the physical division of cave-hunting. _The Biological Division._ We must now proceed to the definition of the scope and object of the second, or Biological, division of the subject.