Part 7 (1/2)
THE ATMOSPHERE.
”And G.o.d said, Let there be an expanse between the waters; and let it separate the waters from the waters. And G.o.d made the expanse, and separated the waters which are under the expanse from the waters which are over the expanse: and it was so. And G.o.d called the expanse Heaven. And the evening and the morning were the second day.”--Genesis i. 6-8.
At the opening of the period to which we are now introduced the earth was covered by the waters, and these were in such a condition that there was no distinction between the seas and the clouds. No atmosphere separated them, or, in other words, dense fogs and mists everywhere rested on the surface of the primeval ocean. To understand as far as possible the precise condition of the earth's surface at this period, it will be necessary to notice the present const.i.tution of the atmosphere, especially in its relations to aqueous vapor.
The regular and constant const.i.tuents of the atmosphere are the elements oxygen and nitrogen, which, at the temperature and pressure existing on the surface of our globe, are permanently aeriform or gaseous. Beside these gases, the air always contains a quant.i.ty of the vapor of water in a perfectly aeriform and transparent condition. This vapor is not, however, permanently gaseous. At all temperatures below 212 degrees it tends to the liquid state; and its elastic force, which preserves its particles in the separated state of vapor, increases or diminishes at a more rapid rate than the increase or diminution of temperature. Hence the quant.i.ty of vapor that can be suspended in clear air depends on the temperature of the air itself. As the temperature of the air rises, its power of sustaining vapor increases more rapidly than its temperature; and as the temperature of the air falls, the elastic force of its contained vapor diminishes in a greater ratio, until it can exist as an invisible vapor no longer, but becomes condensed into minute bubbles or globules, forming cloud, mist, or rain. Two other circ.u.mstances operate along with these properties of air and vapor. The heat radiated from the earth's surface causes the lower strata of air to be, in ordinary circ.u.mstances, warmer than the higher; and, on the other hand, warm air, being lighter than that which is colder, the warm layer of air at the surface continually tends to rise through and above the colder currents immediately over it. Let us consider the operation of the causes thus roughly sketched in a column of calm air. The lower portion becomes warmed, and if in contact with water takes up a quant.i.ty of its vapor proportioned to the temperature, or in ordinary circ.u.mstances somewhat less than this proportion. It then tends to ascend, and as it rises and becomes mixed with colder air it gradually loses its power of sustaining moisture, and at a height proportioned to the diminution of temperature and the quant.i.ty of vapor originally contained in the air, it begins to part with water, which becomes condensed in the form of mist or cloud; and the surface at which this precipitation takes place is often still more distinctly marked when two ma.s.ses or layers of air at different temperatures become intermixed; in which case, on the principle already stated, the mean temperature produced is unable to sustain the vapor proper to the two extremes, and moisture is precipitated. It thus happens that layers of cloud acc.u.mulate in the atmosphere, while between them and the surface there is a stratum of clear air. Fogs and mists are in the present state of nature exceptional appearances, depending generally on local causes, and showing what the world might be but for that balancing of temperature and the elastic force of vapor which const.i.tutes the atmospheric firmament.[68]
The quant.i.ty of water thus suspended over the earth is enormous. ”When we see a cloud resolve itself into rain, and pour out thousands of gallons of water, we can not comprehend how it can float in the atmosphere.”[69] The explanation is--1st, the extreme levity of the minute globules, which causes them to fall very slowly; 2d, they are supported by currents of air, especially by the ascending currents developed both in still air and in storms; 3dly, clouds are often dissolving on one side and forming on another. A cloud gradually descending may be dissolving away by evaporation at the base as fast as new matter is being added above. On the other hand, an ascending warm current of air may be constantly depositing moisture at the base of the cloud, and this may be evaporating under the solar rays above.
In this case a cloud is ”merely the visible form of an aerial s.p.a.ce, in which certain processes are at the moment in equilibrium, and all the particles in a state of upward movement.”[70] But so soon as condensation markedly exceeds evaporation, rain falls, and the atmosphere discharges its vast load of water--how vast we may gather from the fact that the waters of all the rivers are but a part of the overflowings of the great atmospheric reservoir. ”G.o.d binds up the waters in his thick cloud, and the cloud is not rent under them.” It is thus that the terrestrial waters are divided into those above and those below that expanse of clear air in which we live and move, exempt from the dense, dark mists of the earth's earlier state, yet enjoying the benefits of the cloudy curtain that veils the burning sun, and of the cloudy reservoirs that drop down rain to nourish every green thing.
We have no reason to suppose that the laws which regulate mixtures of gases and vapors did not prevail in the period in question. It is probable that these laws are as old as the creation of matter; but the condition of our earth up to the second day must have been such as prevented them from operating as at present. Such a condition might possibly be the result of an excessive evaporation occasioned by internal heat. The interior of the earth still remains in a heated state, and includes large subterranean reservoirs of melted rock, as is proved by the increase of temperature in deep mines and borings, and by the widely extended phenomena of hot springs and volcanic action. At the period in question the internal temperature of the earth was probably vastly greater than at present, and perhaps the whole interior of the globe may have been in a state of igneous fluidity. At the same time the external solid crust may have been thin, and it was not fractured and thickened in places by the upheaval of mountain chains or the deposition of great and unequal sheets of sediment; for, as I may again remind the reader, the primitive chaos did not consist of a confused acc.u.mulation of rocky ma.s.ses, but the earth's crust must then have been more smooth and unbroken than at any subsequent period. This being the internal condition of the earth, it is quite conceivable, without any violation of the existing laws of nature, that the waters of the ocean, warmed by internal heat, may have sent up a sufficient quant.i.ty of vapor to keep the lower strata of air in a constant state of saturation, and to occasion an equally constant precipitation of moisture from the colder strata above. This would merely be the universal operation of a cause similar to that which now produces fogs at the northern limit of the Atlantic Gulf Stream, and in other localities where currents of warm water flow under or near to cooler air. Such a state of things is more conceivable in a globe covered with water, and consequently dest.i.tute of the dry and powerfully radiating surfaces which land presents, and receiving from without the rays, not of a solar orb, but of a comparatively feeble and diffused luminous ether. The continued action of these causes would gradually cool the earth's crust and its inc.u.mbent waters, until the heat from without preponderated over that from within, when the result stated in the text would be effected.
The statements of our primitive authority for this condition of the earth might also be accounted for on the supposition that the permanently gaseous part of the atmosphere did not at the period in question exist in its present state, but that it was on the second day actually elaborated and caused to take its place in separating the atmospheric from the oceanic waters. The first is by far the more probable view; but we may still apply to such speculations the words of Elihu, the friend of Job:
”Stand still and consider the wonderful works of G.o.d.
Dost thou know when G.o.d disposes them, And the lightning of his cloud s.h.i.+nes forth?
Dost thou know the poising of the dark clouds, The wonderful works of the Perfect in knowledge?”
We may now consider the words in which this great improvement in the condition of the earth is recorded. The Hebrew term for the atmosphere is _Rakiah_, literally, something expanded or beaten out--an expanse.
It is rendered in our version ”firmament,” a word conveying the notion of support and fixity, and in the Septuagint ”_Stereoma_,” a word having a similar meaning. The idea conveyed by the Hebrew word is not, however, that of _strength_, but of _extent_; or as Milton--the most accurate of expositors of these words--has it:
”The firmament, expanse of liquid, pure, Transparent, elemental air, diffused In circuit to the uttermost convex Of this great round.”
That this was really the way in which this word was understood by the Hebrews appears from several pa.s.sages of the Bible. Job says of G.o.d, ”Who alone _spreadeth_ out the heavens.”[71] David, in the 104th Psalm, which is a poetical paraphrase of the history of creation, speaks of the Creator as ”_stretching_ out the heavens as a curtain.”
In later writers, as Isaiah, Jeremiah, Ezekiel, similar expressions occur. The notion of a solid or arched firmament was probably altogether remote from the minds of these writers. Such beliefs may have prevailed at the time when the Septuagint translation was made, but I have no hesitation in affirming that no trace of them can be found in the Old Testament. In proof of this, I may refer to some of the pa.s.sages which have been cited as affording the strongest instances of this kind of ”accommodation.” In Exodus xxiv., 10, we are told, ”And they saw the G.o.d of Israel, and under his feet as it were a paved work of sapphire, and as it were the heaven itself in its clearness.” This is evidently a comparison of the pavement seen under the feet of Jehovah to a sapphire in its color, and to the heavens in its transparency. The intention of the writer is not to give information respecting the heavens, or to liken them either to a pavement or a sapphire; all that we can infer is that he believed the heavens to be clear or transparent. Job mentions the ”pillars of heaven,” but the connection shows that this is merely a poetical expression for lofty mountains. The earthquake causes these pillars of heaven to ”tremble.” We are informed in the book of Job that G.o.d ”ties up his waters in his thick cloud, and the cloud is not rent under them.” We are also told of the ”treasures of snow and the treasures of hail,” and rain is called the ”bottles of heaven,” and is said to be poured out of the ”lattices of heaven.” I recognize in all these mere poetical figures, not intended to be literally understood. Some learned writers wish us to believe that the intention of the Bible in these places is actually to teach that the clouds are contained in skin bottles, or something similar, and that they are emptied through hatches in a solid firmament. To found such a belief, however, on a few figurative statements, seems ridiculous, especially when we consider that the writers of the Scriptures show themselves to be well acquainted with nature, and would not be likely on any account to deviate so far from the ordinary testimony of the senses; more especially as by doing so they would enable every unlettered man who has seen a cloud gather on a mountain's brow or dissolve away before increasing heat to oppose the evidence of his senses to their statements, and perhaps to reject them with scorn as a barefaced imposture. But, lastly, we are triumphantly directed to the question of Elihu in his address to Job:
”Hast thou with him stretched out the sky, Which is firm and like a molten mirror?”
But the word translated sky here is not ”_rakiah_,” or ”_shamayim_,”
but another signifying the _clouds_, so that we should regard Elihu as speaking of the apparent firmness or stability, and the beautiful reflected tints of the clouds. His words may be paraphrased thus: ”Hast thou aided Him in spreading out those clouds, which appear so stable and self-sustaining, and so beautifully reflect the sunlight?”[72] The above pa.s.sages form the only authority which I can find in the Scriptures for the doctrine of a solid firmament, which may therefore be characterized as a modern figment of men more learned in books but less acquainted with nature than the Scripture writers.
As a contrast to all such doctrines I may quote the sublime opening of the poetical account of creation in Psalm civ., which we may also take here as elsewhere as the oldest and most authoritative commentary on the first chapter of Genesis:
”Bless the Lord, O my soul!
O Lord, my G.o.d, thou art very great: Thou art clothed with honor and majesty, Who coverest thyself with light as with a garment, Who stretchest out the heavens like a curtain (of a tent), _Who layest the beams of thy chambers in the waters, Who makest the clouds thy chariots, Who walkest upon the wings of the wind_.”
The waters here are those above the firmament, the whole of this part of the Psalm being occupied with the heavens; and there is no place left for the solid firmament, of which the writer evidently knew nothing. He represents G.o.d as laying his chambers on the waters, instead of on the supposed firmament, and as careering in cloudy chariots on the wings of the wind, instead of over a solid arch. For all the above reasons, we conclude that the ”expanse” of the verses under consideration was understood by the writers of the book of G.o.d to be _aerial_, not _solid_; and the ”establishment of the clouds above,” as it is finely called in Proverbs, is the effect of those meteorological laws to which I have already referred, and which were now for the first time brought into operation by the divine Legislator. The Hebrew theology was not of a kind to require such expedients as that of solid heavenly arches; it recurred at once to the will--the decree--of Jehovah; and was content to believe that through this efficient cause the ”rivers run into the sea, yet the sea is not full,” for ”to the place whence the rivers came, thither they return again,” through the agency of those floating clouds, ”the waters above the heavens,” which ”pour down rain according to the vapor thereof.”
G.o.d called the expanse ”Heaven.” In former chapters we have noticed that heaven in the popular speech of the Hebrews, as in our own, had different meanings, applying alike to the cloudy, the astral, and the spiritual heavens. The Creator here sanctions its application to the aerial expanse; and accordingly throughout the Scriptures it is used in this way; _rakiah_ occurs very rarely, as if it had become nearly obsolete, or was perhaps regarded as a merely technical or descriptive term. The divine sanction for the use of the term heaven for the atmosphere is, as already explained, to indicate that this popular use is not to interfere with its application to the whole universe beyond our earth in verse 1st.
The poetical parts of the Bible, and especially the book of Job, which is probably the most ancient of the whole, abound in references to the atmosphere and its phenomena. I may quote a few of these pa.s.sages, to enable us to understand the views of these subjects given in the Bible, and the meaning attached to the creation of the atmosphere, in very ancient periods. In Job, 38th chapter, we have the following:
”In what way is the lightning distributed, And how is the east wind spread abroad over the earth?
Who hath opened a channel for the pouring rain, Or a way for the thunder-flash?
To cause it to rain on the land where no man is, In the desert where no one dwells; To saturate the desolate and waste ground, And to cause the bud of the tender herb to spring forth.”
Here we have the unequal and unforeseen distribution of thunder-storms, beyond the knowledge and power of man, but under the absolute control of G.o.d, and designed by him for beneficent purposes.
Equally fine are some of the following lines:
”Dost thou lift up thy voice to the clouds, That abundance of waters may cover thee?
Dost thou send forth the lightnings, and they go, And say unto thee, Here are we?