7 
resembling decayed wood, about two feet in length, four 
inches in breadth, and varying from half to one inch in 
thickness. On the slightest force being applied, it shelled 
off the stone underneath in a similar way that bark comes 
off the boles of decayed trees. This singular covering did 
not extend around the whole of the stem which was em- 
bedded in the rock, but appeared only on the upper surface 
and reaching a short distance round the sides. It was 
lying parallel to the stratification, but whether it was a 
compressed stem or the bark of aii underlying stem, it is 
difficult to say, but at the time I was inclined to the former 
opinion. 
Bischof, in his Chemical and Physical Geology, vol. I., p. 
42, says that specular iron is a very remarkable petrifying 
material, and gives instances of fossil shells which consist 
entirely of crystalline laminae of specular iron, and that 
fibrous red iron ore was met with by G. Sandberger as a 
petrifying substance at a mine in the neighbourhood of 
Oberscheld, in Nassau. The same author also adds that 
these petrifactions are of no little importance in a geological 
point of view, for they furnish altogether decisive evidence 
that specular and fibrous red iron ores are formed in the wet 
way, whether the oxide of iron occurs in veins or as a 
pseudomorph. 
The same author also states that as the brown iron ore 
in displacement-pseudomorphs, and the material for its for- 
mation can only be furnished by the soluble -bicarbonate of 
iron, it is remarkable that such waters, though frequently 
so occurring, have not oftener caused the petrifaction of 
animal remains. However, according to Zippe (Jahrb. f. 
Mineral. 1843, p. 616), spathose iron ore occurs as a petrify- 
ing material of wood ajb the Postelberg in Bohemia. Wiser 
recently met with black oxide of manganese as the petrify- 
inof material of an ammonite from the mines at Gonzen 
near Sargaus, in Switzerland. 
