FOOTNOTES:
[12] Winchell, “Walks and Talks in the Geological Field,” p. 99.
[13] Winchell, “Walks and Talks in the Geological Field,” p. 275.
CHAPTER VI.
THE EARTH’S HEAT.
That the heat of the earth increases as we penetrate its surface has been learned from mining, tunneling, and the boring of wells. Yet on testing the wells they do not seem to show any uniform temperature. The deepest Artesian well is in St. Louis and has a depth of 3,843½ feet, while its water is found to be of a temperature of 105°.[14] This would seem to indicate that the earth is hotter as we descend into it; still, there may be reasonable causes therefore without its heat extending after all to any great depth. When we remember that the earth is 4,000 miles from surface to centre we find that this deep well is not even 1/5000 part of the distance, and what may be in the interior of the earth is yet quite uncertain. It may possess elements, that from earth’s swift revolutions on its axis, and far swifter flight through space, would supply any loss of heat over and above what is received from the sun. Heat may also penetrate earth’s surface more easily than it escapes, for earth is surrounded by an atmosphere that receives the sunlight readily, but not so readily lets it go; and prevents the outside cold of 200° below zero from falling upon it nightly.
Further it is said, with seeming reasonableness; “No rock has the requisite rigidity to resist the crushing weight of a mountain twenty miles high.” Whatever movements may take place in the earth’s crust, involve masses so great and forces so enormous that the resistances of ordinary matter are inconsiderable. The most solid rocks are essentially fluid or viscid. Now, such movements must necessarily result from two causes: First, a slow shrinkage of the earth through loss of heat; secondly, the attraction of the sun and moon, which cause tidal protuberances on the surface of the earth, however rigid it may be; and these, continually shifting their positions, as the oceanic tides do, result in daily motions adequate to develop a large amount of frictional heat.[15]
This last occasioning of heat we would especially notice, and, perhaps, amply account for the present known heat. If at the bottom of said Artesian well, two-thirds of a mile deep, the temperature is 105°, why is it at the bottom of the ocean, five miles toward earth’s centre, that the water is ice cold? It is admitted that the question concerning internal heat is imperfectly understood. “We neither know,” says Professor Winchell, “at what depth it exists, at what ratio it increases, nor what is its cause or source. Nor do we know whether the deep interior is in a solid or a liquid state. Assuming the rate of increase to be one degree for 60 feet of descent, we should obtain, in the latitude of New York, heat enough to boil water at a depth of about 9,000 feet.” We note that in proportion to the depth of the well it should have a temperature of at least 500°, or a heat that would cause the waters of the ocean overlying three-fourths of earth’s surface to boil; especially in deep waters where there is but little of earth’s sediment, and where its crust must be necessarily thinner than the elevated land.
Again; We are told that the moon is scarred all over with volcanic craters, some of which are 100 miles in diameter; but what volcanic crater on earth could be detected 240,000 miles away by any telescope that magnified 1,000 times, or even be seen by the naked eye at a distance of 240 miles? There are, to be sure, at the present day volcanoes that give evidence of great internal heat, as Etna and Vesuvius. These compared to earth’s vast surface of 200 millions of square miles, and vaster volume, would be no more than a burning leaf in a forest of trees. The many extinct ones show it must have been the same in past ages, but how soon these are seized upon by vegetation and hidden from view! We are told that masses of lava are very poor conductors of heat and have been found burning a century after their eruption.[16] This being the case how long might heat be imprisoned in earth, when it has been stated that cold might not all escape in 7,000 years? May not this imprisoned heat be the source of the escaping of any excessive heat over and above that which earth has received; and all these volcanoes—and the hot springs as well—be caused by smouldering under-ground fires of liquid, gaseous, or solidified heat; generated, we know not how, from either the sun’s or the earth’s heat? For if the sun’s heat can be stored in cold bodies to be used thousands, or even millions of years afterward, may not earth’s escaping heat be likewise returned to earth, and every particle of it be held by earth, as water and air are held by it?
The petroleum, natural gas, and coal that have been little known until the last fifty years, are all lying within one half mile of earth’s surface and of sufficient quantity to make several volcanoes, could oxygen be brought to fan them into a flame. What materials equally as combustible may be discovered when the earth is penetrated in other places, and for another half mile below its surface, we do not know; neither do we know what may be revealed as we descend deeper and deeper into earth’s every portion until reaching a depth of an hundred or a thousand miles. But who shall say there are not as wondrous things yet to come from beneath earth’s crust as have ever been found upon, or near, its surface? Man has already discovered over sixty elements some of which, were they in abundance, would give a very enduring flame. When we see chemists separating water for burning, or consuming steel files in combustion we may be prepared for other startling discoveries. What we already know, through cyclones and hurricanes, concerning the power of air, that is seemingly so subtle and still, should lead us to believe that we have as yet little understanding relative to the hidden truths of earth; and what its interior may possess of heat and other elements is not for us to say with any degree of certainty.
The thought we may now well entertain is this; it is remarkable that the earth’s surface where we are dwelling is well adapted for our existence. At present there is life here; that death was in the past, and destruction will be in the future, we may believe as we choose, but have no certainty of the fact; for the indestructibleness of every atom of ether in the universe would seemingly question the power of time to work destruction to our earth so minute in comparison.
