Philosophical transactions, Vol. L. Part I. For the year 1757. · Various
WOOD.
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.
Ideas discussed in this chapter
Text from Project Gutenberg, public domain in the United States.