In this outline of the history of cave-exploration it will be seen, that the additions to our knowledge of the past have been neither few nor insignificant, nor in one line of inquiry. And if the attention which is now being directed to the subject be due to the general development of scientific thought, it is equally true, that the results have reacted on scientific thought in general, and have especially benefited the sciences of geology, archæology, and history. A rich field of investigation lies before the cave-hunter, in Greece, Palestine, Lycia, Persia, and the limestone plateaux of central Asia; and since these discoveries have been so valuable in central and north-western Europe, what may we not recover from the grasp of oblivion, of the infancy and early culture of mankind in the very birth-place and “pathway of the nations”? CHAPTER II. PHYSICAL HISTORY OF CAVES. Caves formed by the Sea and by Volcanic Action.--Caves in Arenaceous Rocks.--Caves in Calcareous Rocks of various ages. --Their Relation to Pot-holes, “Cirques,” and Ravines.-- The Water-cave of Wookey Hole.--The Goatchurch Cave.--The Water-caves of Derbyshire.--Of Yorkshire.--The Ingleborough Cave.--The Rate of Deposit of Stalagmite.--The Descent into Helln Pot.--The Caves and Pots round Weathercote.--The Formation of Caves, Pot-holes, and Ravines.--Caverns not generally formed in line of Faults.--Of various Ages.--Their Filling-up.-- The Cave of Caldy.--The Blackrock Cave.--Great quantity of Carbonate of Lime dissolved by Atmospheric Water.--The Circulation of Carbonate of Lime.--The Temperature of Caves.-- Conclusion. _Caves formed by the Sea and by Volcanic Action._