DYNAMICAL GEOLOGY. 2O5 



exposed to subaerial weathering, and that some of the fine, 

 loose clays had afterwards sunk into the erosive and pitted 

 surface of the nagelflue rock. In many cases, however, the 

 sand or clay in the pipes undoubtedly represents the insoluble 

 residue left after the removal in solution of the calcareous 

 material in the conglomerate. 



Subterranean caverns always formed a subject of general 

 interest in literature, and have given rise to many traditions 

 and superstitions. The ancients held them to be entrances 

 into the lower world, and the home of nymphs and fauns. In 

 later centuries literature peopled them with all kinds of ima- 

 ginery beings, fairies, dragons, dwarfs, and evil spirits, and 

 ascribed their origin to earthquakes, inthrows of the Earth's 

 crust, subterranean fires and floods. 



Towards the close of the seventeenth century, Leibnitz gave 

 an accurate description of the Baumann cave in the Harz 

 district, and Valvasor examined the caves in Carniola. During 

 the following century, although the number of accurate descrip- 

 tions increased, little advance was made in the explanation of 

 their mode and origin. Kant's Text-book of Physical Geography 

 (1801) attributes the origin of caves partly to the erosion of 

 the rock by water, partly to outbreaks of fire. 



A new epoch in the literature of caves began with Esper's 

 investigation (1770-90) of fossil remains of mammalian bones 

 discovered in the French caves. Interest then centred in the 

 palaeontological significance of the remains in cave-deposits. 

 Cuvier's Recherches sur les ossements fossiles contains an able 

 summary of all existing knowledge on the subject of cave- 

 remains during the first two decades of the nineteenth century. 

 The two brothers Wagner, in Germany, and Buckland by 

 his standard work on the Diluvial Remains of England, 

 worthily followed Esper's example in collecting information 

 and examining ossiferous caverns. The work of Schmirling, in 

 Belgium, won well-merited fame on account of its splendid 

 illustrations ; it was descriptive of the caverns in the province 

 of Liege (1833-34). Marcel de Serres in 1838 published his 

 interesting Essay on the Causes which have contributed to the 

 Accumulation of Fossil Bones in Caves. 



There is now scarcely any difference of opinion regarding 

 the origin of caves. A few caves occur in crystalline or clastic 

 rocks ; they are the result either of tectonic disturbances, or 

 they represent spaces that have formed during the cooling of 



