Chevreul's Report on the Mysterious Oscillations of the Hand-Held Pendulum

The preceding facts and the interpretation I made of them led me to link them with others that we can observe every day. By that concatenation, the analysis of the latter becomes at once simpler and more precise than it was, at the same time they form an ensemble of facts whose general interpretation is susceptible to a wider extension. But before going any further, let us recall that my observations present two main components:

1. To think that a hand held pendulum may move, and that it may move without the holder having any consciousness of the muscular organs giving any impulse whatsoever; that is the first fact.

2. To see the pendulum oscillate, and that these oscillations become more extended through the influence of sight upon the muscular organs, still without any consciousness of the process; that is the second fact.

The tendency toward movement, determined in us by the sight of a moving body, is to be found in several other cases, for example:

1. When attention is entirely directed toward a bird in flight, a stone thrown slicing through the air, running water, the body of a spectator directs itself in a more or less marked manner toward the line of movement;

2. When a player of bowling or billiards follows with his eyes the body he has set in motion, he moves his own body in the direction he wants that moving body to follow, as if he were still able to direct it toward the goal at which he had aimed.

When we walk on a slippery surface, everyone knows how quickly we throw ourselves to the side opposite from that where our body is impelled by a loss of balance; but an occurrence less generally known is that a tendency toward movement manifests itself even when it is impossible for us to move in the direction of that tendency; for example, in a carriage, fear of overturning makes you stiffen in a direction opposite to the threat, and as a result your efforts grow more exhausting and anxiety and irritability increase. I believe that in ordinary falls, letting fall causes less inconvenience than the effort made to prevent the fall. It is in that sense that I understand the truth of the proverb: There is a god for children and for drunkards.

The instance I just cited leads naturally to the case where, being placed on a mountain ledge whose width offers a much broader path than would be strictly necessary if one were walking on a highway, one suddenly comes to realize the depth of the drop below. At the same instant, so to speak, one irresistibly throws oneself to the side opposite the abyss, pushed by the survival instinct that struggles against the tendency to movement in the opposite direction, determined by the sight of the sheer drop. That tendency is also noted when one is on a bridge with no railing, set above a deep gorge; the gorge, looked at from one side, makes you throw yourself to the opposite side, thus subjecting you to the same anxious state as the one you were just attempting to elude. Thus successively stressed in two opposite ways, you are transfixed and reduced to immobility unless the excessive fear of falling on the side where you are makes you run the risk of throwing yourself off the opposite side. Such is, in the case we are discussing, the case of a man who has not been trained to walk on narrow paths overlooking vertical drops, whereas the man who is accustomed to it walks in such places with as sure a foot as on a wide road, because, free of fear, he does not think of the danger that rattles the inexperienced man. Lastly, the latter's position could become even more critical, if he were to discover the depth of the abyss in a situation where, because he was following the flight of bird or a thrown stone, etc., he had already followed up to a certain point that tendency drawing us toward any moving body. [1]