FOOTNOTES:
[10] For example: Take two rooms and heat one as hot as the sun now is what must the cold in the next room be to equalize the heat to 300° below zero?
[11] We do not inquire how the original nebula came into being; our history must commence with the actual existence of this nebula. There is, let it be confessed, a great deal of obscurity still clinging to the subject. Though we may be sure, that the great nebula once existed we cannot with much confidence trace out the method by which the planets were actually formed.
Sir Robert Ball, “In Starry Realms,” p. 348.
CHAPTER V.
THE EARTH’S CRUST.
Were earth’s crust no thicker in comparison than the skin of an apple or peach, or 1/100 of its radius even, still man has never penetrated to one-twentieth of that depth; for I know of no place where he has as yet reached one mile below earth’s general level, unless it be in ocean-soundings. In most places the mines or gorges have been in the mountains high above the valleys, consequently we know little of what is far beneath the earth’s surface. How could we judge of the inside of nuts, fruits, grains, or vegetables if we had penetrated to but one-twentieth of their coverings?
Take, for instance, a chestnut that all boys are familiar with, and see what we may learn from it. We find that it is covered with a tough, brown shell which in turn is enclosed in a large prickly burr ten times the size of the nut. This protects it until ripened and then opens to let the nut fall. The burr is fastened to a large forest tree whose roots are deep in the ground; a tree that had been growing for years before the chestnut was produced, and first started from another nut of its kind. From the time its growth began there was nothing in root, trunk, limb, or leaves for years that in any way resembled a chestnut; nor in the blossom or burr even, until the nut ripened and fell to the ground. Could one think, who had never before seen the nut, that from such a tree a chestnut could be produced?
The same is true of all manner of nuts, fruits, and vegetables. It is even true of animals, for they are enclosed in such varied coverings that their nature is often quite concealed from us. We may as well believe there is something in earth’s interior, away from winds and cold, as precious over and above its crust as the chestnut is better than the burr that encloses it; the fruit better than its rind; or fish, birds, and animals better than their skins. Knowing this, man, while he would grasp the greatness of the universe, may somewhat under-rate the contents of his own earth.
Dr. Winchell in speaking of cold has said; “It has been demonstrated that an ice-cap resting several thousand years over any considerable portion of the surface would so reduce the subjacent temperature of the earth that for many centuries after the disappearance of the ice, a decrease of temperature would be discovered in penetrating downward. Even centuries later, so much cold would still remain within the earth, that the rate of increase of temperature would be less than if the ice-cap had not existed; and after 3,600 years, that rate would be only half the normal rate.”[12]
Now if the earth’s crust will thus retain the cold why may it not as well retain the heat? In that case any excess of heat escaping from earth, over and above the heat it constantly receives from the sun, may be readily accounted for. It is claimed that the earth has large quantities of sunlight and heat stored in a liquid state, as petroleum; in a gaseous state, as natural gas; and in a solidified form, as coal; some of which are found at a depth of 1600 or more feet, although coal is sometimes found near the surface, and even upon the mountains. If these are all stored sunlight, why do they not accumulate over earth’s entire surface as well as in certain localities,—especially in the torrid zone where great heat exists,—and accumulate to-day as well as in former ages?
When we remember that the Mesozoic aeon was preceded by the long Palæozoic, and earlier by the Eozoic,—whose aeon has been laid down at eleven million years, with a strata at least 50,000 feet thick of hardest rock,—what could have been the cause of the submerging of the lands where these gases and coal lay? For millions of years the Eozoic strata had upheld the oceans that were two or more miles in depth, and of enormous weight. If the earth was cooling all those years the crust must have been hardening, and what added weight could have been at so late a period to cause the submerging of those lands? It has been thought that in the glacial period when the accumulation of ice over a portion of earth’s surface lay 5,000 feet thick that its weight might have depressed the terrestrial crust.[13] But ice being lighter than water, even though it were of that thickness, would not have had the weight of water a mile in depth; whereas more than twice that depth of water rested upon three-fourths of the globe. Moreover the ice-period was many millions of years later than the Palæozoic and Eozoic ages, and had the earth all this time been growing colder its crust must have been thickening, making it capable of enduring almost any pressure. Any crust, as ice upon water or the shell upon an egg, will bear more than its whole weight before it will sink into the substance upon which it rests.
It might be thought that earth, while cooling, would shrink beneath its crust and leave a vacuum, as ice sometimes does upon a small surface. This could not happen as the vast surface of extended crust, by the enormous pressure of air upon it, would be held closely pressed to whatever was beneath. For, although earth’s surface is convex, it is still 25,000 miles around it, a distance so great that its crust would have almost the same pressure as if the surface were level.
