68 
ELEMENTS OF GEOLOGY. 
slowly; as in the familiar example of wooden piles or other 
buried timber. Now, if as fast as each particle is set free by 
putrefaction in a fluid or gaseous state, a particle equally mi¬ 
nute of carbonatp of lime, flint, or other mineral, is at hand 
ready to be precipitated, we may imagine this inorganic mat¬ 
ter to take the place just before left unoccupied by the or¬ 
ganic molecule. In this manner a cast of the interior of cer¬ 
tain vessels may first be taken, and afterwards the more sol¬ 
id walls of the same may decay and suffer a like transmuta¬ 
tion. Yet when the whole is lapidified, it may not form one 
homogeneous mass of stone or metal. Some of the original 
ligneous, osseous, or other organic elements may remain min¬ 
gled in certain parts, or the lapidifying substance itself may 
be differently colored at different times, or so crystallized as 
to reflect light differently, and thus the texture of the orig¬ 
inal body may be faithfully exhibited. 
The student may perhaps ask whether, on chemical princi¬ 
ples, we have any ground to expect that mineral matter will 
be thrown down precisely in those spots where organic de¬ 
composition is in progress ? The following curious experi¬ 
ments may serve to illustrate this point: Professor Goppert 
of Breslau, with a view of imitating the natural process of 
petrifaction, steeped a variety of animal and vegetable sub¬ 
stances in waters, some holding siliceous, others calcareous, 
others metallic matter in solution. He found that in the pe¬ 
riod of a few weeks, or sometimes even days, the organic 
bodies thus immersed were mineralized to a certain extent. 
Thus, for example, thin vertical slices of deal, taken from the 
Scotch fir [Pimis sylvestris)^ were immersed in a moderately 
strong solution of sulphate of iron. When they had been 
thoroughly soaked in the* liquid for several days they were 
dried and exposed to a red-heat until the vegetable matter 
was burnt up and nothing remained but an oxide of iron, 
which was found to have taken the form of the deal so ex¬ 
actly that casts even of the dotted vessels peculiar to this 
family of plants were distinctly visible under the microscope. 
The late Dr. Turner observes, that when mineral matter is 
in a “ nascent state,” that is to say, just liberated from a pre¬ 
vious state of chemical combination, it is most ready to unite 
with other matter, and form a new chemical compound. 
Probably the particles or atoms just set free are of extreme 
minuteness, and therefore move more freely, and are more 
ready to obey any impulse of chemical affinity. Whatever 
be the cause, it clearly follow's, as before stated, that where 
organic matter newly imbedded in sediment is decomposing^ 
there will chemical changes take place most actively. 
