Facts tending to illustrate and prove the existence of a mid-plane-space, situated between the concave and convex surfaces of the sphere.

According to Symmes's Theory, each sphere has an intermediate cavity, or mid-plane-space, of considerable extent, situated between the convex and concave surfaces of the sphere, filled with a very light and elastic fluid, rarified in proportion to the gravity, or condensing power of the exposed surfaces of the respective spheres: and also, various other less cavities or spaces between the larger or principal one, and the outer and inner surfaces of the spheres, each filled with a similar fluid or gas, most probably partaking much of the nature of hydrogen. This fluid is lighter than that in which the sphere floats; and has a tendency to poise it in universal space. The spheres, in many parts of the unfathomable ocean, is believed to be water quite through from the concave or convex surfaces to the great mid-plane-space, and probably the earthy or solid matter of the sphere, may in many places extend quite through from one surface to the other, tending, like ribs or braces, to support the sphere in its proper form. Such a formation of spheres appears to be supported by various facts and phenomena; amongst the most prominent of which are Volcanoes and Earthquakes. Many volcanic mountains burst out and burn for ages, discharging from the bowels of the earth immense quantities of lava, pumice, and various substances of various kinds. Some of these mountains have been burning for thousands of years, at least as far back as the records of history have been made known to us.

Had the earth, at its formation, been a solid globe, four times as hard as hammered iron at the centre, and gradually lessening in density towards the surface, we must admit that it would still be solid matter. Governing ourselves by these principles, how can we imagine that such immense caverns, filled with combustible matter, as would be necessary to supply those volcanoes from time immemorial, could have existed? However, that they do exist is certain, which I think is in no way more easily accounted for, than on the plan of a mid-plane-space, or of spaces, filled with a certain hydrogenous gas, which being much lighter than atmospheric air, if there should be any small aperture or crevice extending from the surface to the space beneath, the gravity of the outer part of the sphere pressing on it would occasion a portion of this gas to escape through the aperture; and as it comes in contact with the oxygen of the atmosphere would take fire and occasion those tremendous explosions which we know do sometimes take place and cause those mountains to burn for years, until the cavity which supplied the volcanic matter, becomes exhausted; or until some shock or convulsion consequent on the burning, may have loosened rocks or earth of the denser part of the sphere, which falling into the aperture, choke it up. Hence the gas ceasing to escape, the volcano would cease to burn, until some shock or accident should again open the aperture.

The elastic fluid, with which the mid-plane cavities are filled, being forced out into the common atmosphere, the greater degree of gravity would condense and set free its latent heat or caloric, and be resolved into its original base, somewhat as coal-gas, out of the tube of a gas-light apparatus, yields up its latent heat by condensation. Hence steam burns when mixed with coal-gas.

If the earth be a solid globe, I am at a loss to account for the principles on which earthquakes occur. Long before I heard of Symmes's theory, or perhaps before it had an existence in the mind of man, when reading accounts of earthquakes, it appeared to me altogether unaccountable, that such violent concussions could take place in one part of the world, and not be felt throughout the globe. It appears altogether inconsistent, that one part of a solid piece of matter, would be shaken so violently, without affecting the whole mass. We are informed by authentic history, that whole islands, and vast sections of country, have been sunk by earthquakes, and never more heard of. On the other hand, islands which are now inhabited, and productive, have been raised, apparently, from the bottom of the unfathomable ocean. How such things occur, I am unable to divine. If the globe be solid, on what principle could a large portion of its surface, which is said to be lighter than the parts beneath, sink into a dense medium? How could a heavy mass, lying a thousand fathoms deep at the bottom of the ocean, rise, and be suddenly elevated above the surface of the water, when all below is so compact, and governed by an opposite and immutable tendency? It appears to be a solecism in nature.

The writer had once an opportunity of witnessing some of the effects of earthquakes. It was his fortune to be on the Mississippi river in the year 1812, at the time when that country was so violently convulsed with an earthquake. He saw and heard innumerable explosions, as though a large quantity of air had been confined in the bowels of the earth, and, seeking vent, rushed out with a tremendous sound; forcing up considerable quantities of sand through the apertures, in many instances mixed with black muddy water, and a substance resembling stone coal, or carbonated wood, which emitted a strong bituminous odour, when exposed to fire.

At one place the river was stopped in its course a short time: the water rose to a considerable height above its common level; and, on the west side of the channel of the river, there was a counter-current for a few minutes of an astonishing velocity. So great was its force, that for some distance the cotton wood and willows on the margin of the river, were either prostrated or bent up the stream; and their branches looked as if they had been dragged a long way on the ground. The waters of the river soon subsided, and flowed in their natural direction.

So tremendous were those explosions, that when happening under large trees, the tenacity of their texture yielded at once to their force; and the largest in the forest were split and fractured from root to top. During these convulsions, the ground on which the town of New-Madrid is situated, together with the country for several miles round, sunk about five feet below its former elevation; in which situation it has remained. Eight years afterwards the writer was again on the same spot. The desolate aspect, which the country presented at the time he witnessed those scenes, was measurably obliterated: but the banks of the river were still in their sunken situation.

How could all those violent convulsions take place at this point, and not be felt at New-Orleans, along the sea coast of the United States, and other places? Whence came this water and air, which issued from those apertures in the earth? And why did the river for a few minutes flow in a contrary direction, and then resume its natural course? If the earth be a compact and solid globe, I can account for none of these things; but admitting the formation of the sphere to be such as I contend for, they are all resolved into the most simple principles; and what would otherwise be impenetrable mystery, is made as plain as noon-day. If the sphere be formed as I allege, those concussions were doubtless occasioned by the gas or fluid in the mid-plane or some intermediate space, near the surface, which, by being suddenly rarified, would make it expand, and cause the upper part of the sphere to be suddenly elevated in the neighbourhood of the Little Prairie; and hence the waters of the river, pursuing the laws of gravity, would flow in a contrary direction. This sudden expansion, and elevation of the surface, would cause apertures, through which the rare gas would escape, and the surface would then settle down again, not only to its former level, but, as a considerable portion of this gas had escaped, the remaining part would occupy less space; hence the surface of the country, around New-Madrid, would be below its former situation.[31]

The fluid, or gas, which fills the mid-plane and intermediate cavities, is most probably the same, or partaking of the same nature, (though perhaps in a purer state,) with that which oozes out of fissures in the earth, at the bottom of deep mines, called by chemists, hydro-carbonate; which being highly inflammable, takes fire from the lamps used by workmen, and explodes with such violence as to destroy both men and horses employed in the mine. This is a frequent occurrence in the deep coal mines of England; and great numbers annually have lost their lives in this way, before the introduction of Sir Humphrey Davy's lamp. I am also informed, from good authority, that the miners, in some of the deep coal mines in England, once felt, or heard an earthquake, which happened in Italy, whilst those on the surface of the ground had no knowledge of it. This would be the case, if the intermediate cavity, which caused the earthquake, extended in that direction, and near the bottom of the mine; as it is presumed the rare gas with which those spaces are filled, is better adapted to the conveyance of sound, or vibratory motion, than the more solid parts of the sphere, or even the atmosphere around us.

On the supposition that the globe is solid, and the matter composing it at rest, as respects itself, on what principle can boiling and hot springs be accounted for; some of which issue out several thousands of miles distant from where any volcano or subterranean fire is known to exist; particularly as to those on the waters of Red river, in the state of Louisiana, which are sufficiently hot to cook meat in a few minutes.

Phenomena which occur in various lakes in Europe, may be adverted to in support of this theory. The waters of lake Zirchnitzer, in the Dutchy of Carniola, in Germany, flow off, and leave the basin empty; and again fill it, in an extraordinary and impetuous manner; bringing up with its waters fish and even sometimes wild water fowl.[32] In the same country, there is a subterranean lake, in the Grotto Podspetschio, of considerable extent; the whole of this vast body of water, at certain times, will disappear in a few minutes, and leave the basin dry; and after a few weeks, it again suddenly returns, with a frightful noise. The lake of Geneva, and some others in Switzerland, at certain times rise and fall several feet without any cause, which has as yet been satisfactorily explained; and some writers inform us, that those lakes, particularly Geneva, send forth, at times, a grumbling noise. In the Saian mountains, near the source of the Yenisei, is a lake, called Boulamy-Koul, which, at the approach of winter, emits strange sounds, somewhat similar to those which precede the eruption of a volcano, and which are compared by the neighbouring inhabitants to howling. The inhabitants on the borders of Baikal, also state, that they have often heard dreadful and terrific howlings proceed from that lake.[33] The lake, Agnano, in Italy, sometimes, especially when the waters are high, appears to boil at its borders. This ebullition is supposed to be occasioned by some gaseous fluids, discharged into the bottom, which traverse the waters of the lake.[34] These various phenomena, which cannot be easily accounted for, might be best explained perhaps, on the principles of mid-plane-spaces. In various parts of the north, thick strata of ice are found, under a thick soil; and on ice-bergs, floating in the ocean, have been discovered masses of earth, of granite, and of other rocks.[35]

On the shores of Greenland the ebb tide flows towards the coast, apparently as though it passes under the land, and the flood tide recedes from the shore; and in those regions the sea is almost universally found deeper as you approach the shore.[36] When the whales become scarce, experience has taught the whalers to seek for them near the shore, as if at certain seasons they retired to it, and then disappeared. Captain Symmes imagines that the sea extends quite through the spheres, about Greenland, and that the whales suddenly migrate either to the mid-plane-space, or to the seas on the opposite side; which he alleges to be the case with several other species of fish, as well as seals; all of which, he supposes, breed in the mid-plane-space. The reasons that induce him to adopt this conclusion are various; such as, that fish have been thrown up by the eruption of a volcano in South America[37]—herring appearing in such immense numbers at certain seasons of the year—the whales seeming to pass under Greenland—two seals having been once caught in Lake Ontario, which is said to be unfathomable, although this lake is many degrees south of where the seals have ever before been known to come—and the various species of fish in our northern lakes which appear and disappear at certain periods. That the exterior seas in some places communicate with the interior seas, is rendered probable by various other circumces; such as currents running continually into the Mediterranean, and no visible outlet to the water thus continually flowing in. It is scarcely probable that evaporation could carry off all the water supplied by the straits of Gibraltar—the white sea being more salt at the head than at the foot—the tides being higher in the Baltic than the Mediterranean—white foxes having been forced up by the waters of the sea (as Symmes undertakes to prove) in the northern regions—the peculiarities of the tremendous whirlpool on the coast of Norway, called the Maalstroom, which sucks in, and discharges the waters of the sea with great violence—and those observable in the Bay of Biscay, which are said to be unfathomable.