Physiologia Kircheriana Experimentalis

[...in which] the center of the earth is more easily revealed than under this line. But if it were moved under the line A B, I say that a bird would undergo nothing but a violent motion; for from D it would be carried upward into A, or into B, along a straight line, which is most violent for birds; but the most violent of all is that which occurs along a perpendicular line, such that there is hardly a bird that could sustain it; hence, by a certain instinct of nature, all birds in flight prefer a helical path, whether they are veering upward or downward. Thus, a bird would remain fixed at the very center of the earth, since there is nothing so contrary to birds as upward perpendicular motion; but at the center of the earth, since no ascent is possible from any side except along a perpendicular, it would remain stuck, held fast both by the difficulty of the ascent and by its own center of gravity.

PARADOX IX.

If the seed of any plant were cast into the center of the earth, it would bloom in all directions in the form of a radiant star.

If the seeds of any plant were placed into the masses of the earth and cast into the center of the earth, they could bloom in no other way than in the form of a radiant sphere. For since individual plants naturally, as Kircher said in Book 1, proposition 7 of the Mundus Subterraneus, are carried upward along a line of direction, and since the lines at the center of the earth veer upward on all sides and from every direction, the budding seeds would raise their stalks spherically under those lines, since they could not achieve their end in any other position.

A small six-petaled floral ornament or woodcut flower used as a divider.

PARADOX X.

Fire ignited at the center of the earth is spherical.

For since fire by its nature is carried upward, and at the center it is conceived as being directed upward on all sides and from every direction, it will necessarily, being diffused on all sides, affect a radiant body.

PARADOX XI.

On instituting perpetual motion at the center of the earth.

In this place, I cannot omit the vain contrivances and notable fallacies of certain people who think, or rather strive to demonstrate, that artificial perpetual motion can be achieved in a certain way at the center of the earth, and they endeavor to show this by the following reasoning.

Let there be placed, first, two fulcra G K and H I, together with an axis G H, around which a gnomon A B C, with a leaden ball C attached, is so applied that its vertebra A can be turned around the axis. This being posited, they say it will come to pass that the gnomon A B C, once set in motion, will perpetuate its circular movement around the axis G H, agitated into the circle B D F E. They assign the reason for this as the fact that the leaden ball attached to the gnomon, since it cannot descend along the line of direction C A because it is hindered toward the center A, is perpetually urged by gravity toward D; and thus, having been moved from D toward F, and from F toward E, and from there toward B, since, burdened by weight, it can rest nowhere, it is always about to repeat the circle with new and ever-newer circumvolution, in perpetual motion. And so, they falsely persuade themselves that perpetual motion can occur in this way around the center of the earth.

A geometric diagram illustrating a mechanical paradox. It shows a circular path labeled B, D, F, E with a central axis G-H supported by vertical posts G-K and I-L. A weighted arm (gnomon) A-B-C with a lead ball at C is shown within the circular frame, intended to demonstrate a theoretical perpetual motion machine at the Earth's center.

Having observed this device, which seems plausible at first glance, again and again, I could not help but laugh at the deceptive illusions of the human imagination. Therefore, I have decided to declare how contrary this is to the propositions we have delivered in this book, lest in the future