Symmes's Theory of Concentric Spheres / Demonstrating that the Earth is hollow, habitable within, and widely open about the poles

by James McBride; John Cleves Symmes

The experiments made on the density of the globe, by observations with the plum-line, at the foot of a mountain, are very ingenious; but they must be subject to great uncertainty. The true deviation of the plum-line, the exact quantity of matter in the mountain, or, indeed, the quantity of matter between the plummet and the centre of gravity, are points difficult, if not impossible, to be ascertained with mathematical precision.

If the attraction of the sun is just sufficient to keep the earth in its orbit, what can give the tendency to retain Jupiter and Saturn in theirs, each of which, if solid, contains such a vast quantity more than the earth, and removed to so great a distance from the sun, that his influence upon either must be greatly lessened by both?

2d. As to the objections that a hollow sphere of the dimension of the earth cannot exist in nature, I can discover no sound reason to warrant such a conclusion. Many hollow cylinders and spherical figures, we know do exist on the surface of the earth; and notwithstanding their own gravity, which the different parts exert on each other, as well as the gravity of the earth, they retain their shape and position; and had the matter in the earth originally been thrown by a centrifugal force into the form of a hollow sphere, or had the first creating power originally given it that shape,—I can discover no good reason for a change; neither should I entertain any apprehensions of the particles of matter coalescing at the centre.

3d. The force of this objection I cannot appreciate; for if all the planetary orbs in the universe are composed of hollow concentric spheres, they must exert the same relative influence on each other, which they would if they were solid orbs, as they would each contain the same proportion of matter as respects each other. Hence no good reason appears why a system of hollow concentric spheres might not do just as well, and perform their revolutions with the same regularity, as a system of solid ones.

4th. This great and alarming objection comes next:—that we are about placing a world in eternal darkness, cut off from all the comforts and pleasures of refined life, for the enjoyment of which we are so eminently qualified. Let us examine the force of this objection; and if we cannot show that the interior is, at least in some degree, illuminated, we must then conclude that it is a very dreary abode, and unfitted for the residence of beings so fond of light as we profess to be.

According to the new theory, the northern polar opening is about four thousand one hundred and fifty miles in diameter, and the axis of the earth is at an angle of about twelve degrees with the axis of the plane of the polar opening; consequently, as the sphere revolves on its axis, one side of the verge of the polar opening will extend considerably further north than the other. The verge of the north polar opening on the low side, is laid down at about fifty degrees of latitude, and the verge of the high side at about sixty-eight degrees.

Now, supposing the sun to be exactly of the same diameter as the earth, and placed directly over the equator, when the low side of the verge was turned towards the sun, the direct rays from his northern limb, independent of refraction, would pass the edge of the lower part of the verge, and fall on the inner part of the sphere, on the concave part of the high side opposite, as far as eighteen degrees, or upwards. When the sun would be on the tropic of Cancer, in June, he must then throw the rays from his centre twenty-three and a half degrees further within the sphere, or within twenty-six and a half degrees of the equator; but the diameter of the sun being so much greater than the earth, the rays from his northern limb, would fall about thirty-three minutes further within the sphere, and leave not quite twenty-six degrees between that and the equator to be excluded from his direct rays. This relates to the northern polar opening; as to that of the south, which is believed to be much larger, we will make a few remarks. The lower side of the south polar opening, is laid in about latitude thirty-four degrees, and the higher side, in about latitude forty-six degrees. Were the sun of the same diameter with the earth, as above premised, and placed on the equator, his direct rays would be thrown into the south polar opening when the low side was towards him, about twelve degrees, or to within thirty-four degrees of the equator, and when on the tropic of Capricorn, in December, twenty-three and a half degrees further, that is, the inner part of the southern hemisphere of the sphere, on the high side, would be lighted thirty-five and a half degrees within the verge; and the direct rays of the sun would shine within ten and a half degrees of the inner centre of the sphere or equator. These observations, you will observe, are made in the most unfavourable point of view. It is well known, that the diameter of the sun, is vastly greater than that of the earth; consequently, his rays would pass into the polar opening so much further, in proportion as the angle of his diameter, and that of the earth, differ, which would be about thirty-three minutes further, bringing his direct rays in the south, within less than ten degrees of the equator; and this would be the case as the sphere revolved on its axis, once in every twenty-four hours. When the sphere turned, with its high side towards the sun, it would be night, or twilight, and when the low side was next the sun, it would be day; at all events, the direct rays of the sun would fall on a space of about thirty-six and a half degrees in breadth; the reflection from which would light the whole of the remaining portion of the inner part of the sphere, to a greater degree, than any moon-light with which we are acquainted. But there is another circumstance which tends to throw the rays of the sun much further into the concave than we have yet got them; that is, the refractive power of the atmosphere. It is a well known fact that the rays of light are very much refracted when passing out of a rare into a denser medium; and about the poles of the earth it is believed, (and this belief is confirmed by navigators) that refraction increases very considerably, owing to the great density of the atmosphere. We have good reason then to believe that refraction throws the rays of the sun several degrees further within the sphere. But let us take the known refraction of the horizontal ray, at or near the equator (say one half of a degree) it would throw the rays of light so much further into the concave, and not leave quite thirty-seven degrees in the centre of the sphere deprived of the sun's rays. The motion of the earth causes the apparent motion of the sun to be about fifteen degrees in an hour, as the diurnal revolution of the earth causes the sun to move apparently through three hundred and sixty degrees in twenty-four hours. Now it is a well known fact to all that the sun gives us light sufficient to be called day-light, for about an hour after he descends below the horizon; consequently he must afford us light when he is fifteen degrees obscured from our view. Accordingly, the sun, though he might not be visible, would illuminate the concave part of the sphere fifteen degrees further than his direct rays fall, which reduces the space in the interior of the sphere to the breadth of not quite seven degrees which would still remain unlighted.

But this is making calculations on the most unfavorable premises possible. Considering the form of the earth, and the power of refraction, I have no doubt but the direct rays of the sun would fall on every part of the inner sphere. However, I have proceeded on such premises as, I conclude, the most sceptical must admit. Light, we know, is reflected from solid bodies on which it falls, and also from the atmosphere: the rays of the sun, then, which would pass the lower part of the verge and fall on the opposite concave surface, would be reflected back in all directions, and most probably light the whole of the interior of the sphere sufficient for the ordinary purposes of life. By way of further illustration, suppose a perpendicular wall were raised on a plain, one mile high, does any person believe that there would be no light on the side of the wall opposite to the sun; although his rays would have to form an angle of one hundred and forty, or one hundred and fifty degrees, to reach the earth on that side of the wall? No axiom is more evident than that the rays of light are communicated to other places than those on which the rays of the sun fall directly; for example, we all know that a close room, however large, with a north window, will be sufficiently lighted by refraction and reflection from the atmosphere, provided there is no obstruction opposite the window, although the rays of the sun would have to form an angle of one hundred and fifty degrees to enter it, and why might not the whole interior of the sphere be lighted in the same manner, even supposing the rays of the sun should never enter directly. The north polar opening being about four thousand one hundred and fifty miles in diameter, and the southern six thousand three hundred and fifty, with the whole force of the direct rays of the sun falling on and passing through the atmosphere at either polar opening, it would not require refraction, or reflection, to make an angle of ninety degrees to light the whole of the interior concave; and certainly the polar openings are sufficiently large for the purpose, when we compare a common window with the dimensions of an ordinary sized room.

It is believed, by the adherents of the new theory, that the atmosphere, within the concave, and about the polar openings, is much denser than our atmosphere; which appears inevitably to be the case, as the centrifugal force on the convex has the tendency to throw the atmosphere from the surface, and on the concave to force it from the centre of motion, and nearer to the surface. This admitted, the rays of the sun passing out of a rare medium into a denser, would be refracted much further into the sphere; and the sun-shine on the surface of one sphere would be reflected obliquely, according to the angle of incidence, to the next sphere, and in this manner might be extended even beyond the centre of the concave. It is also believed, that near the verges of the polar openings, and perhaps in many other parts of the unfathomable ocean, the spheres are water quite through, (at least all except the mid-plane-spaces, or cavities) which being the case, light would probably be transmitted between the spheres.