Archæology, also, by the use of strictly inductive methods, has grown from a mere antiquarian speculation into a science; and its students have proved the truth of the three divisions of human progress familiar to the Greek and Roman philosopher, and expressed in the pages of Hesiod and Lucretius--the Ages of Stone, Bronze and Iron. The subdivision of the first of these into the older, or palæolithic, and newer, or neolithic, by Sir John Lubbock, is the only refinement which has been made in this classification. Sir Charles Lyell has discussed the various problems offered by the general consideration of the first of these divisions in “The Antiquity of Man;” while Sir John Lubbock, in “Prehistoric Man,” has followed Dr. Keller and others in working out the past history of mankind by a comparison of the habitations, tombs, implements and weapons found in Europe, with those of modern savages. This work is intended to be to a considerable extent supplementary to theirs,--to treat of the formation of caves, and of the light thrown by their contents on the sojourn of man in Europe, on the wild animals, and on the changes in climate and geography. In treating of the caves of the historic period, I have given considerable prominence to the exploration of the Victoria Cave, near Settle, which has led to the discovery that many caverns were inhabited in this country during the fifth and sixth centuries, and that they contain works of art of a high order. In the difficult task of bringing them into relation with British history and art, I have to acknowledge the kind assistance of Mr. E. A. Freeman, the Rev. J. R. Green, and Mr. A. W. Franks. In the neolithic division of the prehistoric period, I have published at length my recent discoveries in the sepulchral caves of Denbighshire, and am allowed by my friend, Professor Busk, to reprint his description of the human bones. To his suggestive essay on the Gibraltar caves, as well as to the works of the late Dr. Thurnam, and of Professors Broca and Huxley, I am indebted for the clue to the identification of the neolithic dwellers in caves with the ancient Iberians or Modern Basques. That portion of the evidence which relates to France I have verified by a personal examination of the human remains from caves and tombs in the Museums of Bordeaux, Toulouse, Lyons and Paris. The results of the exploration of the Hyæna-den of Wookey Hole have been given in greater detail in the portion of the work devoted to the palæolithic age than they would have been, had they been before fully recorded. And in this division of the subject I have largely made use of the “Reliquiæ Aquitanicæ,” which embodies the discoveries in Auvergne of my late friends Professor E. Lartet and Mr. Christy. To the editors of that work I am indebted for permission to use some of the plates and letterpress.