BASALTIC GROTTOES AND CAVES. 



Mirrabel, in the Yivarais, descending towards St. Jean 'le JSoir, 

 fiar. 38. 



Fig. 30. 



Ficr. 3.9. 



96. Grottoes, caves, and tunnels are often found in the midst of 

 these basaltic masses, and in those of trap rocks, which have a 

 close analogy to them. Examples of this may be seen in the Viva- 

 rais, on the borders of the Rhine, near Bertrich-Baden, between 

 Treves and Coblentz, where the columns forming the grotto con- 

 sist of rounded blocks superposed, resembling a pile of cheeses, 

 from whence the grotto has received the name of Kase Grotte, or 

 Cheese Grotto, fig. 39. But by far the most magnificent of these 

 basaltic grottoes is the celebrated Cave of Fingal, in the Island of 

 Staffa, fig. 37, p. 49. 



Fig. 39. The Kase Grotto of Bertrich-Baden. 



97. Another eruptive product of the terrestrial crust, still more 

 extensive than the basalt, is the trachytic rocks, which form the 

 celebrated Puy-de-d6me, in Auvergne, the Mont D'or, the Cantal, 



79 



