Sea-side and Way-side.LESSON I.EARTH-BUILDING.“Fair world! these puzzled souls of ours grow weakWith beating their bruised wings against the rimThat bounds their utmost flying, when they seekThe distant and the dim.“Contentment comes not therefrom; still there liesAn outer distance when the first is hailed;And still forever yawns before our eyesAn utmost that is veiled.”—Jean Ingelow,Honors.
Sea-side and Way-side.
EARTH-BUILDING.
“Fair world! these puzzled souls of ours grow weakWith beating their bruised wings against the rimThat bounds their utmost flying, when they seekThe distant and the dim.“Contentment comes not therefrom; still there liesAn outer distance when the first is hailed;And still forever yawns before our eyesAn utmost that is veiled.”
“Fair world! these puzzled souls of ours grow weakWith beating their bruised wings against the rimThat bounds their utmost flying, when they seekThe distant and the dim.“Contentment comes not therefrom; still there liesAn outer distance when the first is hailed;And still forever yawns before our eyesAn utmost that is veiled.”
“Fair world! these puzzled souls of ours grow weakWith beating their bruised wings against the rimThat bounds their utmost flying, when they seekThe distant and the dim.
“Fair world! these puzzled souls of ours grow weak
With beating their bruised wings against the rim
That bounds their utmost flying, when they seek
The distant and the dim.
“Contentment comes not therefrom; still there liesAn outer distance when the first is hailed;And still forever yawns before our eyesAn utmost that is veiled.”
“Contentment comes not therefrom; still there lies
An outer distance when the first is hailed;
And still forever yawns before our eyes
An utmost that is veiled.”
—Jean Ingelow,Honors.
The starry heavens do not exist merely for us or for our earth. Among the splendid orbs which roll in space, earth is but one, and it shines with pale and borrowed light.Unnumbered systems moved upon their courses before our globe was lighted by the sun. But, for us who live upon the earth the history of the Universe opens with this small planet, a part of which we see and know.
It seems to us, when we begin to inquire about our earth-home, that it must always have been a complete and finished world, just as it now is. Science denies this. Geology leads us far back, before time began to be reckoned here, and shows us some of the processes of world-building. Time was when this firm, beautiful, and life-filled earth was a vast sphere of gas, destitute of all its present order, and without germs of life. As the palace or the temple rises into beauty and harmony out of vast masses of material, such as wood, stone, brick, mortar, iron, and course after course is laid up in the building according to a definite pattern, so along the process of earth-building, force and matter, power and material, have been laying up the courses of the earth upon a uniform plan.
And is the earth now finished? That we cannot say; there may be many more astonishing changes yet in store for it. We are now apt to call it the “solid earth,” because those parts of it with which we are acquainted, the soil and the rocks, are the most solid things that we know; but in plain fact the earth may still be partly liquid, with the exception of a comparatively thin crust. The distance through this ball, our earth, is nearly eight thousand miles, and the surface, or crust, is perhaps nowhere over a hundred miles thick. Thus we might typify the world[1]bya metal ball, having a thin shell of solid metal, and filled with melted metal. But as this crust, thin as it is in comparison, has for many thousand years proved thick enough and safe enough for a dwelling-place for men, I think we need not feel any anxiety because it is not thicker.
To read the story of this earth-building, it has been necessary for science to begin at the end; that is, at the present time, which is the last chapter of the story. With long and patient care wise men have read back, page by page, the earth-building story; we cannot say to its beginning, but as far back as science has yet been able to go. Now we are able to take up the narrative at such beginning as has thus far been found, and read it forward to our present day like a plain story. Will this be interesting? It seems to me that it is like some magnificent fairy tale, more marvellous than the story of Aladdin’s Lamp, or Sinbad the Sailor, or The Caliph of Bagdad. The nights of Arabian story were not half so full of wonders as the days and nights, the vast periods, of geologic story.
Our earth is a globe in rapid motion. The motion is dual, i.e., double; it rolls over and over upon its axis as you might spin a ball round on a knitting-needle thrust through its centre; but the ball on the needle would stay in its place, no matter how many times it whirled over. The earth, as it whirls, rolls along a great path. Every time it turns over it measures off on this path a distance equal to its own circumference, but at the same time it sweeps on with the motion of the whole system, so that each day it travels over a million and a half of miles. The earth’s path is not in a straightline; it is nearly circular; it is what is called elliptical, or partly egg-shaped. As far back as we can trace earth-history, the twofold motion and the globe shape have belonged to our planet.
In the earliest state of which we can speak, our earth was a globe of gas at least two thousand times as large as it now is. Science has made a guess that, before this, our earth was a ring or layer of vapor around the sun. This ring, being spun off into space by the rapid motion of the sun, took, after a time, the sphere shape, and being held by the attraction of the sun from wandering farther off into space, has ever since whirled around in a great path about its ancient source. If this theory be true, then all the other planets of our system were probably once cast off in their order by the sun, as vast fiery rings. That must have been an age of grand and splendid fireworks indeed! If only one had been there to see!
Why cannot we imagine that we were there to see? Can we not fancy ourselves back, through all the wonderful ages, until we reach the beginning of all things? The Arabians have a kind of fanciful being, whom they call an Afrite, or Afreet. They say that this being is formed of pure heat, smokeless flame. Did any of you ever see, on a very scorching day, the air quivering above a dry, hot road? That quivering of hot air is often seen on the desert, and the Arabians say it is the waving of an Afrite’s robe. Let us fancy we were Afrites, gigantic flame-spirits, present when the earth, from a fiery ring, had just become a fiery ball.
Heat, such as we cannot imagine, is the chief characteristicof our globe at this stage. But being Afrites, and ourselves made of heat, we shall not mind that. We see that the whirling hot ball has in it all the atoms which will one day become solid rocks. But these atoms are kept apart by heat, and are in a state like gas. As we Afrites peer at the glowing, whirling ball, we see that there are two forces at work within it. Heat is one force, keeping all particles expanded, and not letting them come together; but there is another force called gravitation at work also. This is a force which causes all things to tend toward each other—to draw together. It is this force of gravitation which first gives the gaseous ring its globe shape, pulling its particles together; and as Afrites, we watch with interest the results of this force by long and slow degrees condensing the matter of the globe.
While this is going on, we perceive that two great changes are taking place. First, the sphere is growing cooler, by radiating, or throwing off its heat. Heat a poker red hot; wave it in the air, and it cools by giving off its heat to the air. Thus the hot globe throws off some of its heat as it whirls along its path in space. But as the sphere cools, the loss of heat allows the particles to shrink and come together and unite with each other. The uniting of some of these various simple substances produces other substances, and as the cooling and uniting go on, the great globe becomes smaller and smaller. As we are Afrites, and not afraid of heat, we wander into this fluid ball, and we find that by all this cooling, condensing, and uniting, the material for future rocks is forming.
Still imagining ourselves Afrites, the next change does not please us as well. We find that the outer particles of vapor in our great hot ball, as they ascend into space and cool, unite with each other and become a vapor like steam, and this steam cools and condenses into rain and mist. If a plate is held before the nose of a tea-kettle from which steam is rushing out, the steam condenses at once into drops of water. If the plate with the water-drops on it is set out in sharply cold winter air, it is at once covered with frost or ice. Thus it happened with the vapor about that hot sphere, our world; and the rain and mist fell back upon the glowing ball from which they had risen. They helped to cool it and to increase the hardening, but they were also reheated and sent off again as vapor, to cool once more in space.
If at that time we, as Afrites, had travelled to some other planet, and taken a seat there to watch our world from a distance, we should then have seen it in its greatest beauty as a heavenly body, because in that age it was at its greatest size, and was far larger than now: also it must have shone as a clear and lovely star, with a glory which has now almost passed away.
In the illustration at the head of this chapter the large ring represents the earth as a vast ball of hot vapor. The very small ring in the centre shows the present size of the globe as compared with its first expansion. The circle marked1shows the earth as a simple sphere of vapor, its earliest condition. The circle2shows us the stage where, by the force of gravity, and the cooling resulting from the radiation of heat, the sphere of gas began to have a fluid centre, or core.We must understand that the condensing particles in the centre were not rendered solid, but fluid, as you may see the molten glass or iron at a glass-works or iron-foundry. This fluid state probably still continues at the centre of the earth. Figure3shows us the condensation going on. As the globe cools, a solid crust, markedx, is formed around the fluid centre, and between the centre and the crust the matter of the globe is hardening, while the outer envelope beyond the crust is still gas.
Figure4shows another change. The vapor has cooled and condensed in space, and has fallen back upon the globe in rain and snow. These rains corrode and wash the surface of the crust, and finally by their excess cover the whole crust of the earth with an ocean, markedo. Thus the liquid centre and the solid crust are wrapped in a mantle of water. This universal ocean is not cold and clear as are the oceans of to-day. The intense heat of the globe has made these waters boil and send off dense clouds of steam, and thus the water-wrapped world is further enveloped in a veil of mist.
Would it then have been hidden from our sight if we had been Afrites, watching it as we sat on some far-off planet? No; we should have seen it still, grown smaller and paler perhaps, but the mist-veil would have caught and reflected the sunlight, as the clouds do at sunset.
This was the reign of the waters upon the surface of the globe, while the central fires were burning and rolling in the abyss beneath the waters and the hardened earth-crust. When we say fires, of this interior heat, we must not think of flames, but rather of such heat as that of molten metal ina furnace. The universal ocean that wrapped the world at this time was full of salt and earthy matter and was turbid, as a river in flood time. From the deposit of this matter upon the earth-crust, rock strata or layers were formed.
Figure5shows us still another stage of earth-building. The reign of the waters is disputed by the long-imprisoned heat. This heat exerts its force, and tugs and lifts at the earth-crust until it bulges and cracks and rises up, or, as we say, is elevated. Earthquakes and volcanoes alternately depress or upheave a part of the earth’s surface. Great depressions are formed, into which the waters gather, while the thick earth-crust is tilted up into mountain chains, markedz, which are reared above the waters. These wrinkling folds of the crust are the world’s first dry land.[2]
At that time we, as Afrites, would have flown from our distant planet back to the earth, and have laughed to see the fire or heat driving away part of the water from the surface. We should have danced with glee to see the volcanoes pouring out ashes and cinders, and to watch the cinders crumbling and changing and beginning to form new rocks and lighter soil. And so at last we should have seen our earth formed, a rude earth, rough and bare, its seas warm and muddy, its mountains treeless, its fields without a single blade of green, a veil of mist all about it. And how long did it take to complete all this? No one can answer. No one can number the years of creative ages. Earth-building is nota process that can be hastened. After the globe had reached the state which we have now indicated, vast successive changes took place until our own time. Science has divided the succession of these changes into periods or ages, and at these periods we shall now glance, as at some marvellous panorama.
FOOTNOTES:[1]This theory is not universally accepted; some consider that the interior of the earth by cooling and pressure may be in a much harder than molten state.[2]At the present time the interior of the earth has probably become much more solid than in the earlier building ages. We reallyknowlittle of it below a depth of a few miles from the surface.
[1]This theory is not universally accepted; some consider that the interior of the earth by cooling and pressure may be in a much harder than molten state.
[1]This theory is not universally accepted; some consider that the interior of the earth by cooling and pressure may be in a much harder than molten state.
[2]At the present time the interior of the earth has probably become much more solid than in the earlier building ages. We reallyknowlittle of it below a depth of a few miles from the surface.
[2]At the present time the interior of the earth has probably become much more solid than in the earlier building ages. We reallyknowlittle of it below a depth of a few miles from the surface.