AN UNDERGROUND EXCURSION. 



147 



earth's crust has cracked the shaly roof ; the opposite sides 

 of the fissure have been moved to and fro over each other, 

 and under the mighty pressure the two opposing faces have 

 been beautifully polished. 



But probably different sights will greet our eyes. The 

 rocky ceiling is ornamented every where by the most ex- 

 quisite tracery — inim- 

 itable representations 

 of the delicate fronds 

 of ferns (Fig. 64). We 

 remove a scale of the 

 rock, and behind is 

 still another picture. 

 Remove a second, and 

 from the dark black 

 rock gleams forth an- 

 other form of grace 

 and beauty. The 

 whole mass of the 

 shaly roof is a port- 

 folio of inimitable 

 sketches. The sharp- 

 est outlines and mi- 

 nutest serratures of 

 the leaves are clearly 

 traced. The very 

 nerves, with their 

 characteristic bifurca- 

 tions, are accurately 

 depicted on this won- 

 derful lithograph. 

 Petioles, and buds, 

 and woody stems, and 

 cones, and fruits, slender grass-leaves, striated rushes, the 



