110 Geological Society of London. 
instituted a series of most curious experiments, and his success in 
producing imitations of fossil petrifactions has been very remarkable. 
I have only space to allude to one or two examples. He placed 
recent ferns between soft layers of clay, dried these in the shade, 
and then slowly and gradually heated them, till they were red hot. 
The result was the production of so perfect a counterpart of fossil 
plants as might have deceived an experienced geologist. According 
to the different degrees of heat applied, the plants were obtained in 
a brown or perfectly carbonized condition, and sometimes, but more 
rarely, they were in a black shining state, adhering closely to the 
layer of clay. If the red heat was sustained until all the organic 
matter was burnt up, only an impression of the plant remained. 
The same chemist steeped plants in a moderately strong solution 
of sulphate of iron, and left them immersed in it for several days: 
until they were thoroughly soaked in the liquid. They were then 
dried and kept heated until they would no longer shrink in volume, 
and until every trace of organic matter had disappeared, On cool- 
ing them he found that the oxide formed by this process had taken 
the form of the plants. Prof. Géppert then took fine vertical slices 
of the Scotch fir, Pinus sylvestris, and treated them in the same 
way ; and‘so well were they preserved, that, after heating, the dot- 
ted vessels so peculiar to this family of plants were distinctly visible. 
A variety of other experiments were made by steeping animal and 
vegetable substances in siliceous, calcareous, and metallic solutions, 
and all tended to prove that the mineralization of organic bodies can 
be carried much farther ina short time than had been previously 
sup 
These experiments seem to open a new field of inquiry, and will, 
I trust, soon be repeated in this country. In endeavoring, however, 
to verify them, the greatest caution will be required, or we may 
easily be deceived. We must ascertain, for example, with certainty 
that every particle of animal or vegetable matter is driven off before 
we attempt to determine the full extent to which mineralization 
may have proceeded. Prof. Géppert is doubtless aware that conif- 
erous wood may be burnt and reduced to charcoal, and after having 
been kept for some time at a red heat, will contintie to exhibit, on 
being cooled, the discs or reticulated structure to which he alludes. 
If, therefore, some small particles of carbon remain in the midst 
of the oxide of iron, such portions may retain traces of the vessels 
peculiar to coniferous wood ; and an observer not on his guard, might 
infer that the same structure was — the mass. 
