LESSON XIII.
WRITTEN IN ROCKS.
“There rolls the deep where grew the tree,O earth, what changes thou hast seen!There where the long street roars, hath beenThe eternal stillness of the sea.“The hills are shadows, and they flowFrom form to form, and nothing stands;They melt like mist, these solid lands,Like clouds they shape themselves and go.”
“There rolls the deep where grew the tree,O earth, what changes thou hast seen!There where the long street roars, hath beenThe eternal stillness of the sea.“The hills are shadows, and they flowFrom form to form, and nothing stands;They melt like mist, these solid lands,Like clouds they shape themselves and go.”
“There rolls the deep where grew the tree,O earth, what changes thou hast seen!There where the long street roars, hath beenThe eternal stillness of the sea.
“There rolls the deep where grew the tree,
O earth, what changes thou hast seen!
There where the long street roars, hath been
The eternal stillness of the sea.
“The hills are shadows, and they flowFrom form to form, and nothing stands;They melt like mist, these solid lands,Like clouds they shape themselves and go.”
“The hills are shadows, and they flow
From form to form, and nothing stands;
They melt like mist, these solid lands,
Like clouds they shape themselves and go.”
—Tennyson,In Memoriam.
We have been studying for some time about earth-building. We have learned a little of how the rocks and the soil of our globe were formed. What is that study of earth-building called? It is called Ge-ology, which means earth-lore or history, for the old Greeks called the earth Ge, and ge-ology just means the story of earth-making.
But in these lessons we have been talking not of the rocks and earth-beds, but of the gnome-treasures hidden therein, the bones, patterns, stone images, burial cases of things that lived long ago. This is a new study, and is a very important branch of geology; for unless we learn about these old organisms and understand what they tell us, we cannot well learn our geology. These fossils shut up in the rocks are the writings or pictures which keep the story of the long ago. This study has been given the long name of Palæontology—it merely means the study or lore of fossils.
But pray what are fossils? We have heard much aboutthem. What are they? The word fossil really means a thing “dug up.” Once it was applied to any kind of mineral substance. Now we mean by fossil organized substances or their imprints, which have been preserved in any natural fashion, that is, not by the art of man, but by nature.
The study of fossils embraces the study of all forms, from the most ancient here in the rocks of the Dawn, or first period, to those which may have only been buried for a few score of years.
Thus you may see in a cabinet a bit of limestone full of ancient foraminiferæ, and near it a fossil clam from some bed in southern New Jersey, which was producing living clams one or two hundred years ago.
The study of fossils does not assert any limit as to the grade of an organism. A fossil may be some large and curious fish, a rare bird, a beautiful stone lily, or merely a lump of resin which long ago dropped from some tree of the coal period.
So also, we have fossil leaves, fruits, roots, fossil rain-marks, fossil footprints, fossil worm-casts and burrows, and little fossil cases of caddis-worms. Some very valuable fossils are called coprolites; these are the droppings of digested or partly-digested food of animals, and they are valuable because they often contain traces or portions of plants or animals, upon which these other creatures fed, and which now would be entirely unknown unless preserved in this way.
The vulture has a habit of swallowing mice, little birds, and similar prey, with small ceremony of breaking or tearing; they go into the vulture’s maw feathers, fur, bones, and all.When fully gorged, the vulture sits in a meditative manner on a tree, and finally, in the process of digestion, the food parts of what it has eaten separates from the bone and feather refuse, and this latter is rolled into a ball and disgorged by the vulture. I have found such balls, probably a year or two old, bleached white and dry, and unrolling them have laid bare tiny skeletons, perfect, and white as ivory, of the feet and heads of mice. Now if mice had disappeared, it is evident that their skeletons, found in portions in such remains would be valuable, affording us a knowledge of an otherwise unknown creature. So the coprolites tell us their tale of the smaller fauna of the ancient lands and oceans.
The term fossil is not limited to any especial method or state of preservation. In regard to preservation there are three principal varieties of fossils. First: All or nearly all the animal matter may have disappeared, and mineral matter may have taken its place; so that the organism is mineralized or petrified. This is the condition of the majority of fossils. Second: It may have happened that the entire organism has decayed, and as the animal matter when it perished was not rebuilt with mineral deposit, only a cast or natural lithograph of the former living thing remains in the rock. Third: The animal or plant may have been preserved unchanged for hundreds or thousands of years, so that the very creature, with its bones, flesh, hair, even the soft portions of the body, as the brain and eye-ball, may remain complete. This has happened in a few instances, as where ice or frozen mud has been the preserving agent, so that in Siberia certain animals, as the mammoth, have been disentombed after a burial ofthousands of years. Of course as soon as these frozen fossils have been exposed to air and moisture, they begin to fall to pieces, and speedily only the hard parts, as the bones, are left.
In most animal fossils only the bony or shelly portions, which consist largely of lime, have been petrified. Thus we find many fossil skeletons. Sometimes there has been a change on this wise: the action of water has carried off, grain by grain, the lime as well as the animal matter of the organism, and while it thus took the object to pieces, it rebuilt it in a similar way, adding grain by grain of flinty matter, or even of metal, so that in countries where silver abounds, fossil plants have been found cased in silver. I have seen some fossil bones of recent origin, as they were taken from an ancient burial-mound, and the marrow of the bones had been carried off by the action of water and replaced by delicate, shining crystals, so that the hollow or marrow portions of the bones shone as if filled with broken glass.
The chief agents in the decay of animal and plant organisms are air, rain-water, and atmospheric moisture, as dew, mist, and frost. We can see the destructive effects of air in the case of canned meats or fruits. If the sealing of the can is imperfect, the air penetrates, and carries some germ which corrupts the contents. All the vegetable remains that cover the ground each autumn, do not accumulate year after year, but speedily decay and become soil. The animals and insects, large and small, that die in the fields and woods each year, do not long remain where they fell; carnivorous birds and small animals, especially ants and beetles, devour the softportions, and a few years of exposure to air and moisture reduce the bony skeletons to powder. As the thing that is, is generally the thing that hath been, and shall be, we may conclude that nearly all the animals and plants of each age perished with their age, and that what remain as fossils are but a small fragment of the whole, and have been preserved in unusually favorable circumstances.
DONE IN STONE.
DONE IN STONE.
Ice, as we have seen, has served as a wonderful preservative, but the instances where animals or plants have been subjected to the ice-process are naturally few. Next to ice, peat mosses have exhibited remarkable preserving qualities, and have kept entire remains, as deer, bison, oxen, buried in them. Heavy beasts becoming mired in the peat, have sunk into it to a great depth, and were hermetically sealed from the oxygen of the air, and from spores calledbacteria[29]which are the chief agents of decay. Many fossil organisms are preserved in the silt or débris at the mouths of rivers, where the deposit of earthy matter carried down the stream is rapid, and speedily buries up whatever is dropped upon it. On the floors of lakes also, there are often deep deposits of marl, peat, and sand, and these sometimes bury and preserve the bodies of birds or other animals, and the seeds, branches, or entire plants, that have been swept into the water. Caverns, especially those in limestone or chalk rock, have proved famous treasure-houses of fossils. Where, in these caverns, there is a dripping of water charged with lime or chalk, it speedily encloses objects in a safe case which effectually preserves them. Sometimes also these bone caves, ancienthomes of wild beasts, have been closed up by silt or earth-falls, and have retained many specimens of large, ancient fauna now extinct.
But no place has proved so favorable for fossil remains as the bed of the sea. The rapid deposit of sediment on the ocean floor and the remoteness from changes of heat and cold, have made the old ocean beds, such as we visited in our mountain of fossils, a wonderful storehouse of the life-forms of distant ages. The mollusks, corals, and crinoids furnish us the most varied and beautiful fossil remains, and in some cases the preservation is so perfect, that traces are retained of even the former colorings of the shells of mollusks and the scales of fishes that lived in the remotest times.
The grand march of life has been an ascending series, andfor our knowledge of this line of ascent we are indebted to fossils, which tell in successive strata of the earth the history, not only of the changes in the earth’s crust, but of the animal and vegetable life of different periods.
No doubt only a very, very few of the fossils that are hidden in the treasure-houses of earth and sea, have ever been found. There are millions of strange and beautiful things that have never met mortal eye.
Let us sleep and dream. Let us dream that we have built a great and splendid museum, and lined it with shelves and cases. Let us dream that we have found a ring that once belonged to King Solomon, which gives us power over all gnomes and genii. Let us dream that we open wide all the doors and windows of our museum and stand in the midst and clap our hands, and command the genii and gnomes to bring us the treasures hidden in rock, sand, and sea, in lake and river and peat moss and earth beds.
They come! They come! They fly through the air, gnomes, pixies, afrites, fairies, genii, and they fill every shelf and case of our museum with fossil forms and pictured rocks and sands, and give us examples of every animal and vegetable that lived so long ago. How rich and happy now are we! We wake: our dream has fled: the airy walls and shelves and cases of our museum are gone: the gnomes and their brethren, the treasures untold, are vanished with our sleep. What have we left? Nothing? Yes, the best that we can have; industry and observation—these are better than the magic ring and seal of Solomon.
FOOTNOTES:[29]Bac-tee-re-a. These are really unicellular plants.
[29]Bac-tee-re-a. These are really unicellular plants.
[29]Bac-tee-re-a. These are really unicellular plants.