The kinds of wood found fossil are very different: some are of a firmer
texture than others: and this too is according to the places wherein
they are deposited. Some I have seen so highly impregnated with a fine
stony and pyritical matter, as to bear a polish like a pebble; some,
tho’ quite reduced to stone, yet preserving the fibrous appearance of
the original state; and some which is found in boggy bottoms, being
not at all changed, except in color: this is called bog oak, or bog
deal, well known to country people in many places of these three
kingdoms, who light themselves about their business with slips of this
wood, cut on purpose instead of candles, as it burns with a clear and
durable flame. It is remarkable, that altho’ oak or fir shall lie ages
immersed in water under ground, it shall not putrify; but acquire
such sulphureous particles by lying in steep, in the bog-water, as to
qualify it for this use. Other wood, deposited in marly ground, is
found incrusted over, trunk and branches, with a white crust; the wood
remaining intire within. At other times, wood thus incrusted shall be
eroded by the matter which covers it, having something acrimonious in
its substance. We may add to these, clusters of the twigs of shrubs,
and small wood, which we find flakes of, incrusted with sparry or
calcarious matter, in many places; parts of which are totally changed
into that matter, whilst others are only inveloped with it.
BONES _of_ ANIMALS.
We see, by every day’s experience, that the human skeleton moulders
to dust in a very few years, when buried in mould: so it does even
in vaults, where the coffins are kept dry. In the first case, the
moisture and salts of the earth divide and dissolve the texture
of the bones; in the latter, those of the air, which gradually
insinuate themselves into them, and at length destroy them. How long
a skeleton whose bones are well dried and prepared, being totally
deprived of its medullary substance, will last, as we now order them
for anatomical purposes, we cannot say: but it may be reasonably
conjectured, that they will undergo the fate of the softer kinds of
wood, such as beech, which grows rotten in no great number of years;
because their internal substance is spungy and cellular, and their
crust is very thin, except about the middle of the bones of the arm
and thigh, I mean the humerus and fœmur. The same destruction would
happen, if bodies were deposited in a sandy soil; because water finds
its way either by dripping downwards, or by springs underneath. But
human skeletons have been found intire within a rock, where neither
moisture nor air could get at them. Mr. Minors, an eminent Surgeon
and Anatomist of the Middlesex-hospital, when he was in the Army, at
Gibraltar, saw an intire skeleton, standing upright, in a dry rock,
part of which had been blown up with gunpowder, in carrying on some
works in the fortifications, which left the skeleton quite exposed.
Indeed, the bones of Elephants have been found in Shepey-Island, but
much destroyed, several of which I have in my Collection; an account
of which we have in the last volume but one[206] of our Transactions;
their size and substance being so considerable, as to resist for a long
time that decay which those of the human could not withstand. To these
we may add the horns of large animals, as the elk, and others, which
have been found in bogs, preserved as the bog-oak, _&c._ mentioned.
TEETH _and_ PALATES _of_ FISHES _and other Animals_.
These are of so hard and firm a texture, as to suffer no great change,
wheresoever found; for we see, that no erosion appears in them, their
enamel and its polish being intirely preserved; yet sometimes their
roots will be found changed, especially in the yellow ones, having no
enamel to guard them in their roots.
_Parts of_ VEGETABLES.
The leaves of plants, whose fibres are firm and dry, will endure for a
long time; but those of a succulent nature never can, as they putrify
very soon. We see the leaves of ferns of several kinds, polypodium,
tricomanes, and other capillary plants, with nodules of stone formed
about them; flags, reeds, rushes, equisetum, and many such, of a firm
texture, are found in slate and stone; and even the iuli of trees are
said to have been found fossil as well as their leaves.
SEEDS _and_ FRUITS.
All seeds and the stones of fruits, having a firm texture, are also
capable of being strongly impregnated with stony and pyritical matter;
and I make no doubt but that the smaller seeds, if carefully looked
for, might be found fossil, as well as these before you; such, I mean,
as have a firmness in the covering; but being small, and mixt with
the dirt, sand, and the like, probably is the reason of their being
overlooked. Fruits of various kinds are found petrified; but this is
only in their green state, when they are hard enough to endure till
they are impregnated with stony or mineral particles. The rudiments
of fruits, when once well formed, and a little advanced, are firm and
acid: and the more remote they are from maturity, the more secure
from putrifaction; and their acid juice is no small help to their
preservation from growing soon rotten. But indeed, when the fruit
advances in growth, the texture grows gradually more lax; the acid
juices are now beginning to be replaced by saccharine or others more
soft; the fibres are driven farther asunder, and they now arrive at
their most ripe state: and the utmost maturity of fruits is the next
step to putrifaction. Hence they are destroyed before stony or other
particles can have time enough to impregnate them: and this is exactly
the case with the flesh of animals of every kind. The husks and hard
calyces of fruits, as well as their stones, are also susceptible of
petrifaction.
If these fruits, which I have the honour to lay before you, are
antediluvian, one would be apt to imagine they, in some measure, point
out, with Dr. Woodward, the time of year in which the deluge began;
which he thinks was in May: and yet this very opinion is liable to some
objections; because altho’ fruits capable of being petrified, from
their green state, may be pretty well formed in May here, as well as in
the same latitude elsewhere, in favour of this opinion; yet there are
the stones of fruits, found fossil, so perfect, as to make one imagine
they were very ripe, when deposited in the places where they are
discovered; which would induce one to think the deluge happened nearer
Autumn, unless we could think them the productions of more southern
latitudes, where perhaps their fruits are brought to perfection before
ours are well formed.
What follows is a catalogue of these fossil fruits &c. before you: and
I should be glad, if any of the gentlemen would take the trouble of
examining them, in order to assist in our conjectures about such of
them, as appear doubtful: but first beg leave to insert the following
remark:
I cannot omit an observation of Doctor Mason, Woodwardian professor,
in this place; which is well worth notice, and indeed which I never
attended to. It regards the impressions of fishes upon slate. Now
there are several kinds of slate, which have such impressions upon
them: in some there remains only the bare impression, without any
part of the fish; in others the scales only, but retaining the intire
form of the animal; and in others no part adheres to the slate, but
the skeleton, or part of it, most commonly the spine. He says that he
always observed, that the bones are never seen but upon the grey or
blue slate, or their impressions; and that the scales or skin are to be
found only upon the black stone or slate; which makes him conjecture,
that something erosive in the grey slate destroys every part but the
bony system; but that the black, being of a more soft and unctuous
nature, preserves the scales, and often the very skin. This, however,
must be referred to further observation.
[Illustration: _Philos. Trans. Vol. L._ TAB. XV. _p. 403_.