389 



these crystallizations are, in general, only among those filaments 

 of wood which have entirely lost their original nature. The bark 

 is distinguishable, being about four lines in thickpess. There are 

 two layers, one of which is of an azure blue, the other of a pale 

 green, approaching to verdigris. This wood was taken from the 

 mines in the neighbourhood of Souxsons. Mons. D'Auteroche was 

 informed, on the spot, that they sometimes found, in the strata of 

 these mines, entire trees. The specimens he brought home, he took 

 from a collection which occupied the greatest part of a room, which 

 was more than twenty feet long. This wood, he observes, contains 

 more or less copper, according to the places where it has been 

 found ; and displayed various appearances, with respect to colour, 

 but always possesses either green, or azure blue*. 



An examination of the several specimens of fossil copper wood, 

 which I am happy in possessing, shows that the impregnation is 

 made by a carbonate of copper, which appears in several places in 

 its most beautiful form, that of malachite. The brilliance of their 

 colours, the completeness of the transmutation, and the perfect 

 preservation of their original forms, place these specimens among 

 the most beautiful and interesting of the vegetable secondary fossils. 

 One small specimen, described at Fig. 19 in Plate VI. is highly inte- 

 resting, on another account. On its surface, the charred wood, and 

 spots of malachite, are discernible, in several parts, whilst a trans- 

 verse section shows its substance is formed of copper pyrites, of a 

 metallic lustre, displaying, by the striae and circles with which it is 

 intersected, an indisputable ligneous structure. 



Whilst speaking of the impregnations of fossil wood with iron, I 

 spoke of those, which, although evidently containing that metal, 

 did not hold it in that proportion as to admit them to be distin- 

 guished by the epithet metallic. A specimen of fossil wood, which 



* Voyage en Siberie, en 1761, par M. 1'Abbe Chappe d'Auteroche. tome i. 2* partie, 

 p. 671. 



