Physiologia Kircheriana Experimentalis

[...and] others exhaust themselves in useless labor in demonstrating this.

First, therefore, they posit those two fulcrums G K and H I, together with the axis G H, and they think that the axis and the fulcrums have the same position relative to the center of the earth as they have on the surface of the same, which is ridiculous and a mockery of false imagination. For if the fulcrums could be arranged around the center of the earth, they would certainly not take on a position perpendicular, as on the surface of the earth, but rather the opposite, namely, oblique and verging upward. Just as one half of the axis, G A, would tend upward, and the other, H A, would likewise tend upward. If, therefore, there were affixed to the extreme parts of the axis, G and H, plumb lines equipped with leaden weights, it would certainly appear that they could by no means fall downward according to the position of the fulcrums, since they are outside the line of direction. They will fall, therefore, into the center A, where they will rest. Since the fulcrums, therefore, tend upward against nature, they cannot remain in place.

Having shown these things, let us now see whether a gnomon, rotatable around the axis G H, can achieve perpetual motion. Let it move, therefore, if it be possible, from C to D along the arc C D. But since this motion, being violent, consists outside the line of direction A C, it is impossible for the motion to continue without a new impulse. The gnomon will therefore stand with the sphere affixed to it at any point of the circle B D F E, which I demonstrate thus: Because the entire complex of the gnomon A B C behaves as a solid mass, according to definition 3 and canon 4, the center of gravity will be at I, and consequently, wherever it is placed, it will remain, because the center of gravity I perfectly coincides with the line of direction, as was demonstrated at length in the first section. But let it be moved of its own accord from C to D, and from here to F. I ask now, either this mass will be at rest, or it will not be at rest: if it is at rest, we have already obtained our intent; if it is not at rest, as the dealers in perpetual motion wish, then it will never obtain the end of its desire, which is contrary to definition 3, since every movable body moves only in so far as it intends the end of its desire, which is rest, acquired under the line of direction. The gnomon, therefore, will be fixed at every point of the circle B D F E, since for as many points as are conceived in it, there are as many lines of direction, all of which are drawn through I, the center of gravity of the gnomon; therefore, the gnomon will be at rest at whatever point of the circle it is placed upon, and consequently it cannot move of its own accord between the points unless it is drawn into them. Nor does it signify anything to the matter that a sphere is falsely imagined to preponderate and always strive toward the front; since such preponderation does not occur by a natural motion toward the front, but toward the center A, through the line of direction subjected to it; which is also openly clear from the preceding Paradoxes. For if a channel were made around the center of the earth, twisted into the circle B D F E, and a sphere were placed in it, it is certain that it would not be moved perpetually once set in motion, but would come to rest at any place in the channel. The same must be understood regarding water scattered within the channel, which would not flow, but would hold itself with rest under the lines of direction without motion. Therefore, what I had first assumed, that perpetual motion at the center of the earth in the stated manner is impossible, is what had to be demonstrated.