28 



unknown to our botanists ; the existing plants, to which 

 the others seem to approximate, are some of those of the 

 warmer climates. 



III. CUPREOUS FOSSIL WOOD. 



1. PyriticaL This fossil is distinguishable from the 

 ferruginous pyritical wood, by the pyrites being of rather 

 a darker colour, but chiefly by the blue or green colour 

 which partially pervades the fossil. 



In some specimens, in which the general appearance is 

 that of bituminous wood, the metallic impregnation can 

 only be detected by the weight of the fossil and the blue or 

 green hue on its surface. 



2. Wood converted into carbonate and hydrate of copper. 

 Cupreous wood in this state forms very beautiful spe- 

 cimens, displaying, not only on its surface, but in its sub- 

 stance, mingled with the charred wood, the most vivid 

 blue and green colours, with patches of the carbonate in the 

 state of malachite. 



The finest specimens of cupreous wood are obtained 

 from the copper mines of Siberia. 



3. Wood mineralized by lead. Specimens of wood con- 

 taining galena, the sulphuret of lead, have been chiefly 

 discovered in Derbyshire. 



The leaves of plants, except those of gramina, junci, and 

 of the cryptogamia, are seldom found in a mineralized state. 

 The lobes and pinnulae of ferns, as has been before men- 

 tioned, are frequently found in a bituminized state in 

 nodules of ironstone, and in immense quantities with the 

 remains of gramina and succulent plants in the schistose 

 and slaty coverings of coal. 



Among the numerous remains of plants very few are 

 found which agree in their specific characters with any 

 known species, and many indeed differ so much as to render 

 it difficult to determine even the genus under which they 

 should be placed. 



