4. The theory of the continued increase of heat, according to the ratio noticed as you sink a shaft a few hundred feet into the Earth’s crust, if it proves anything proves too much, and is therefore false. Experiments extensively made in the Virginia mines of Nevada, and particularly in the Foreman Shaft, show the increase to be very uneven; differing from one degree in twelve feet to one in two hundred feet. It even grows colder as you descend some kind of rock, a degree in one hundred feet. The degree of heat is always regulated and gauged by the rock you pass. If the rock will disintegrate readily, it gives out more heat; but if the rock may lie exposed in the sun and rain without disintegration, it throws out no heat in the shaft. Yet from experiments made in the Foreman Shaft, notwithstanding these varieties of rock, yet at the 2,100 foot level it is found that the average increase is one degree in twelve feet. At this rate, at twenty-five miles towards the center you would encounter heat above 4,300 deg. Fahr. Chemists will admit that, after due allowance for pressure at such a depth, yet the granite with all known substances would fuse at this heat. The Plutonic hypothesis makes the crust in Nevada less than twenty-five miles, perhaps the weakest on the continent. Experiments in Mexico, upon this line of reasoning, would make the crust twice as thick. Now from a well established law in philosophy, a pressure upon liquid on the inside of a cylinder imparts its pressure to every part of the cylinder at the same time. A pressure capable of breaking the crust in any place should, at least, cause all the openings to emit lava at the same time. But this is not the historic action of volcanoes; one emits while another sleeps. It is a historic fact observed within the present century, that a volcanic mountain rose up from a comparatively level plane in Mexico, in one night, to the height of 1,695 feet. On the assumption that lava comes from the center of the earth, why should not the above pressure have found the weaker crust, and Nevada have been the place of eruption instead of Mexico? and why should not the three hundred open vents of Earth have emitted lava at the same time? The theory will not bear philosophic tests. The Russian report of the increase of heat is only one-fourth that given in Nevada. Who believes, therefore, that the crust there is four times as thick as in Nevada? The whole subject shows that the increase of heat in the shaft proves nothing as to the interior of Earth, and nothing as to the thickness of its crust.