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?