e botanist and chemist have as yet
been unable to explain fully the manner in which wood becomes petrified,
it is nevertheless ascertained that, under favorable circumstances, the
lapidifying process is now continually going on. A piece of wood was
lately procured by Mr. Stokes, from an ancient Roman aqueduct in
Westphalia, in which some portions were converted into spindle-shaped
bodies, consisting of carbonate of lime, while the rest of the wood
remained in a comparatively unchanged state.[1066] It appears that in
some cases the most perishable, in others the most durable, portions of
plants are preserved, variations which doubtless depend on the time when
the mineral matter was supplied. If introduced immediately, on the first
commencement of decomposition, then the most destructible parts are
lapidified, while the more durable do not waste away till afterwards,
when the supply has failed, and so never become petrified. The converse
of these circumstances gives rise to exactly opposite results.

Professor Goppert, of Breslau, has instituted a series of curious
experiments, in which he has succeeded in producing some very remarkable
imitations of fossil petrifactions. 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 cooling them he found that
the oxide formed by this process had taken the form of the plants. 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 in a short