Symmes's Theory; comprehending his description of the form of the earth, and of the other orbs in the Universe; his principles of gravity, and the points wherein he differs from the old or generally received theories.

According to Symmes's Theory, the earth, as well as all the celestial orbicular bodies existing in the universe, visible and invisible, which partake in any degree of a planetary nature, from the greatest to the smallest, from the sun, down to the most minute blazing meteor or falling star, are all constituted in a greater or less degree, of a collection of spheres, more or less solid, concentric with each other, and more or less open at their poles; each sphere being separated from its adjoining compeers by space replete with aerial fluids; that every portion of infinite space, except what is occupied by spheres, is filled with an aerial elastic fluid, more subtile than common atmospheric air; and constituted of innumerable small concentric spheres, too minute to be visible to the organ of sight assisted by the most perfect microscope, and so elastic that they continually press on each other, and change their relative situations as often as the position of any piece of matter in space may change its position: thus causing a universal pressure, which is weakened by the intervention of other bodies in proportion to the subtended angle of distance and dimension; necessarily causing the body to move towards the points of decreased pressure.

It is a sound principle of philosophy, that the particles of the common air of our atmosphere are of a repellant quality, and mutually repulse each other. The whole system of pneumatics goes to prove that air presses equally in all directions. Not a single experiment in this branch of natural science can be performed that does not depend on such a property. This being the case, if the boundless extent of the universe, beyond the limits of our atmosphere, be an entire vacuum, why should the atmosphere be retained in its present circumscribed form, and not expand, by virtue of its repellant quality, far beyond its known height? To prevent this, Symmes believes universal space to be filled with an elastic fluid, inconceivably rare, and uniformly distributed throughout; differing from common air, and from the elastic fluids (which also are known to be repellant) existing in our atmosphere. This tendency is what Symmes believes should be understood by the term gravity; the laws of action governing which he holds to be true, as defined by Newton: and he moreover holds that the application of the laws of gravity, as laid down by Newton, leads a reasoning mind to the belief of concentric spheres, with open poles, as all planetary bodies are in his opinion formed.

In regard to the effects of gravity, he pretends not to differ from the generally received opinion of the age; but the application of them, as to the inner parts of insulated bodies, has enabled him to improve in a knowledge of the formation of planets; and finally led him to form a correct idea of what constitutes gravity.

The author of the new theory entertains a belief that the principles of planetary orbicular forms, developed by him, extend as well to the molecules of the most subtile fluids, as to the innumerable stars or suns of the universe, and all their planetary trains: he contends that though he may not have discovered any new principles in physics, yet that he has made interesting advances in a knowledge of the application of what was heretofore known.

According to him, the planet which has been designated the Earth, is composed of at least five hollow concentric spheres, with spaces between each, an atmosphere surrounding each; and habitable as well upon the concave as the convex surface. Each of these spheres are widely open at their poles. The north polar opening of the sphere we inhabit, is believed to be about four thousand miles in diameter, and the southern above six thousand.[1] The planes of these polar openings are inclined to the plane of the ecliptic at an angle of about twenty degrees; so that the real axis of the earth, being perpendicular to the plane of the equator, will form an angle of twelve degrees with a line passing through the sphere at right angles with the plane of the polar openings; consequently the verge of the polar openings must approach several degrees nearer to the equator on one side than on the other. The highest north point, or where the distance is greatest from the equator to the verge of the opening in the northern hemisphere, will be found either in the northern sea, near the coast of Lapland, on a meridian passing through Spitsbergen, in about latitude sixty-eight degrees, or somewhat more eastwardly in Lapland; and the verge would become apparent, to the navigator proceeding north, in about latitude ninety degrees.

The lowermost point, or the place where the distance is least from the equator to the verge of the northern polar opening, will be found in the Pacific ocean, about latitude fifty degrees, near the north-west coast of America, on or near a meridian running through the mouth of Cook's river, being in about one hundred and sixty degrees west longitude, the real verge being in about latitude fifty degrees and becoming apparent to a person travelling northward at right angles with the magnetic equator, at the distance of about twelve hundred miles further. The verge varies progressively from the lowest to the highest point, crossing the north-west coast of America between latitude fifty-two and fifty-four, thence across the continent of North America, passing through Hudson's Bay and Greenland, near cape Farewell; thence by mount Hecla to the highest point; thence tending gradually more to the south, across the northern parts of Asia, at or near the volcanoes of Kamtschatka, and along the extinguished volcanoes of the Fox Islands, to the lowermost point again, near the northwest coast.

In the southern hemisphere, the highest point, or place where the distance is greatest from the equator to the verge of the polar opening, will be found in the southern Pacific ocean, in about latitude forty-six degrees south, and perhaps about longitude one hundred and thirty degrees west; and the lowermost point, or place where the distance is least from the equator to the verge of the opening, will be found on a meridian south or south-east of the island of Madagascar, in about latitude thirty-four degrees south, and longitude about fifty degrees east; thence passing near the cape of Good Hope, across the Atlantic ocean, and southern part of the continent of America, through a chain of active volcanoes, to the highest point; thence bearing regularly toward the lowest point, passing between the two islands of New-Zealand, or across the most southerly one, and the northernmost part of Van Dieman's land, to the lowest point, which is south or south-east of Madagascar; the apparent verge being several hundred miles beyond the real verge.[2] Consequently, according to this formation of the sphere, the degrees of latitude, on different meridians, will vary according to their distance from the polar openings; and the magnetical equator, which encircles the sphere, parallel to the plane of the polar openings, would cut the real equator at an angle of twelve degrees. A person standing on the highest part of the apparent verge would appear to be under the polar star, or nearly so, and at the ninetieth degree of latitude. The meridians all converge to the highest point of the verge, or the ninetieth degree; consequently, in tracing a meridian of longitude, you would pursue a direction at right angles to the equator, until you arrived in the neighbourhood of the real verge of the polar opening, when the meridians would change their direction and turn along between the real and apparent verges towards the highest point, until they all terminated at the ninetieth degree of latitude; this being the direction a person would travel in order to have his back to the sun always at 12 o'clock, the time of his greatest altitude. Although the particular location of the places where the verges of the polar openings are believed to exist, may not have been ascertained with absolute certainty, yet they are believed to be nearly correct; their localities having been ascertained from appearances that exist in those regions; such as a belt or zone surrounding the globe where trees and other vegetation (except moss) do not grow; the tides of the ocean flowing in different directions, and appearing to meet; the existence of volcanoes; the "ground swells" in the sea being more frequent; the Aurora Borealis appearing to the southward; and various other phenomena existing in and about the same regions, mark the relative position of the real verges.

The heat and cold of the different climates are governed by their distance from the verge of the polar opening, and do not depend on their nearness to or remoteness from the equator. The natural climates are parallel to the planes of the polar openings, and cut the parallels of latitude at an angle of twelve degrees. When the sun is on the tropic of Capricorn, the circle of greatest cold would be about twenty-three and a half degrees south of the apparent verge, and when the sun is on the tropic of Cancer this circle would probably be just under the umbrage of the real verge: hence it follows, if this doctrine be correct, that the climate of forty degrees north latitude on the plains of Missouri, in the western part of the continent of America, will be as cold in winter, as the latitude of fifty or fifty-two degrees in Europe; and observation has fully confirmed such to be the fact.

The magnetic principle which gives polarity to the needle, is believed to be regulated by the polar openings, and that the needle always points directly to the opening, and of course parallel to a line drawn perpendicular to the plane of the opening. And when the apparent verge shall be passed, the needle will seem to turn nearly round, so as to point in an opposite direction; having the contrary end north on the interior of the sphere, that was north on the exterior, the same end being north on the interior which was south on the exterior. Hence, when navigators arrive in the neighbourhood of the apparent verge, the variation of the needle becomes extreme; and when the verge is passed, the variation is more or less reversed. The meridians run from the highest northern to the highest southern point on the verges; hence, in tracing a meridian, or sailing due north, we would pursue that line which would conduct us directly from the sun at his greatest altitude; and when we come to the verge, the meridian would vary, and wind along the vicinity of the edge of the real verge, until it brought us to the highest point of the apparent verge. The magnetic needle, on arriving at the verge would appear to cease to pursue the same direction, but would in reality continue to maintain it, and lead directly into the polar opening.

According to this formation of the sphere, a traveller or navigator might proceed true north any where west of the highest point of the verge, say on the continent of America, until he come to the verge. The meridian on which he was travelling would then wind along the verge to the right, until he arrived at the ninetieth degree; and by proceeding south, in the same direction, he would arrive at the coast of Siberia, without going far into the concavity of the sphere, and without knowing that he had been within the verge. Should such a journey be effected, it would appear to confirm the old theory of the form of the earth, and put the subject at rest; although pursuing the needle might have directed the traveller into the interior, and enabled him to discover those fine countries which Captain Symmes alleges to exist there.

Each of the spheres composing the earth, as well as those constituting the other planets throughout the universe, is believed to be habitable both on the inner and outer surface; and lighted and warmed according to those general laws which communicate light and heat to every part of the universe. The light may not, indeed, be so bright, nor the heat so intense, as is indicated in high northern latitudes (about where the verge is supposed to commence) by the paleness of the sun, and darkness of the sky; facts, which various navigators who have visited those regions confirm; yet they are no doubt sufficiently lighted and warmed to promote the propagation and support of animal and vegetable life.

The different spheres constituting our planet, and the other orbs in creation, most probably do not revolve on axes, parallel to each other, nor perform their revolutions in the same periods of time; as is indicated by the spots on the belts of Jupiter, which move faster on one belt than another.

The atmosphere surrounding the sphere is probably more dense on the interior than the exterior surface, the increased pressure of which must increase the force of gravity; as the power of gravity must increase in proportion as we approach nearer the poles.—Clouds formed in the atmosphere of the convexity of the sphere, probably float in through the polar openings, and visit the interior, in the form of rain and snow. And the long continuation of winds, or regular monsoons, which occur in some parts of the earth, may be supplied by winds sucked into one polar opening and discharged through the other, thus performing the circuit of the sphere; without which supposition, it would be difficult to account for the long continued winds which, at certain seasons, are known to blow constantly for several months, more or less obliquely to and from the poles.

The disciples of Symmes believe that each sphere has a cavity, or mid-plane space near the centre of the matter composing it, filled with a very light, subtile, elastic substance, partaking somewhat, perhaps, of the nature of hydrogen gas; which aerial fluid is composed of molecules greatly rarified in comparison with the gravity of the extended or exposed surfaces of the sphere. This mid-plane space tends to give the sphere a degree of lightness and buoyancy. Besides this large mid-plane space, perhaps numerous other interstices exist in the sphere nearer the surface, and of more limited extent. The gas escaping from these spaces is, no doubt, the cause of earthquakes; and supply the numerous volcanoes. This gas becoming rarified and escaping, must occasion most of those great revolutions and phenomena in nature, which we know to have occurred in the geology of the earth. This aerial fluid with which the mid-plane spaces are filled, may possibly be adapted to the support of animal life; and the interior surfaces of the spheres formed by them, may abound with animals, with organs only adapted to the medium which they are destined to inhabit.

In many parts of the unfathomable ocean there may be communications or passages from the surface of the sphere on the outer side to the surface of the inner, at least all except the great mid-plane space, through which liquid apertures, light and heat may be communicated, perhaps, to the interior surface of the sphere.