The Cohesion of Things

⁵⁹ Not rarely the cohesion of things—at least a secondary one that arises from and presupposes another—can and indeed ought to arise from the gravity of the air. For it is established by experience that 2 planes can hardly be pulled apart if they fit together exactly, because the weight of the incumbent atmosphere must be overcome by the one who would lift it.

The same reasoning applies to 2 curved surfaces—indeed to all surfaces—which touch each other beyond a single point, so that they cannot be pulled apart along a line non-parallel to the congruent surface unless the weight of an aerial cylinder of equal base, subtended by the congruent plane, is overcome.

Because when two things move away from each other so that at the first moment of departure they leave more interval than the air can fill in the same time—because, that is, the entry of the surface is initially smaller than the departure of the surface (which happens whenever the contact is more than at a single point)—there is in the meantime more space empty of air, and consequently more aether enters; and in the meantime the atmosphere must be lifted…

[61]

…lifted or compressed by a certain concurrence of gravity and elasticity: for whichever you call upon, it is the same. And so it is credible that in hard or thin bodies a secondary consistency very often arises, since it is probable that most things fit together more broadly than at mere points. But nevertheless, this consistency presupposes another prior one, as I said. For when a surface is to be torn away from a surface in a line not parallel to the congruence, it is manifest that this is done not by a push, but by traction—that is, by the pulsing of a thing connected elsewhere, namely through a handle or some other prominence curved in the opposite direction. But this connection already presupposes consistency.

For example, if you wish to separate two highly polished tablets in a way other than by a parallel push (which is easy), it is necessary that a handle connected to it, or something else by which you can grasp it, should project from the overlying one. The reason why it is connected must be given. The ultimate reason for consistency, therefore, cannot be sought with Democritus from that congruence, or—as some of another school speak—from a flight from a vacuum (which nevertheless arises least from the thing itself, but rather from gravity and elasticity); much less with Descartes from rest alone, but from the motion of the thing (see above sections 2 & 11). Even if sensible consistencies from composites of this kind—tablets of every shape—are seen to arise not rarely except by the departure [of surfaces] overcoming the gravity and elasticity of the air impressed by that [motion]. Certainly, from the principle of gravity and elasticity…

[62] …the restorative force in bodies, the explanation of compression; the reduction of things drawn apart to themselves must be led partly by spontaneous sense, partly by things remembered, and partly by things to be noted. We perceive this force not only in liquids in closed vessels, such as water, air, etc., but also in those things which are vessels unto themselves—that is, in consistencies of such a kind that are neither absolutely hard nor absolutely soft, but hold a certain middle ground.

• Liquid is that which receives its limits from any other thing, lacks its own, and is separable and transfigurable with the greatest ease.

• Hard (Durum) is that which holds the opposite.

• Flexible is the medium between liquid and hard, which is separable or transfigurable, but not most easily.

• Its species are Glomerable, which even if very easily transfigured, cannot be dissolved with the greatest ease, like a linen or silk thread and others of that kind.

• Soft (Molle) is that which yields for a short time to a transfiguring force, but does not react against it.

• Tenacious (Tenax) is that which strongly resists a transfiguring force but does not react against it.

• Tense (Tensum) is that which resists a transfiguring force and reacts against it, and even restores itself when dismissed.

The notion of a liquid is easy by itself, since its parts are freely mixed together. Of a hard body: when it is composed like flat, congruent boards at every sensible point or surface, from which a board is not lifted at all from another board, or if it is lifted a little, the whole board is lifted. Similarly, hard things either are not bent perceptibly (although I would believe that a subtle bending exists in most of them), or when bent, they break completely.

Soft and tough differ in degree; therefore, the cause of both is the same.

Tough (or stretchable) is either self-restoring or merely simply ductile, like wax or pitch. Simple ductility consists of a perpetual interweaving and insertion into one another, at every sensible point, of little cords, little tubes, little pipes, little boxes, coils, vessels, and other such things, which indeed do not oppose being pulled apart, yet they differ—provided they do not resist due to excessive intertwining. In some things, one can understand this as the cause of hardness, like threads entangled in a mass, a knot having been made, so that soon they are loosened only by breaking.

But in simply ductile things, no confusion ever follows. When drawn out, ever smaller tubes are inserted into one another—equally in all directions, both concavely and convexly, through countless doublings—until, by excessive drawing and excessive thinning, a break occurs.

Nor should this insertion seem marvelous to anyone, since nearly every subtle growth occurs fiber-wise through these doublings and through internal tube-like absorption rather than through external application to the surface of what is being nourished.

Tension adds to the insertion…

[64]

…they are introduced, open: once this is done, they will perform the function of infinite pistons (piston-rods), for although the piston in this place is hollow and open, where it is turned toward the vessel exhausting air, it nevertheless suffices for it to be sealed on the part where it opposes the vessel.

Now that the thing is drawn apart and equipped with these tubes, it is necessary for that difficulty in drawing apart to be felt in proportion to what is felt in pulling out a piston while we exhaust air from pneumatic vessels.

When the force of the one drawing apart a tense thing relaxes, it is necessary for it to restore itself with the same force by which a piston, suddenly released during extraction, is pushed back into the vessel.

Nothing is clearer, nothing easier, nothing more agreeable to our hypothesis as the cause of this tension propagated through all the insensible pistons continuously inserted into one another—though unequally, according to distance.

In bodies, just as a force diffused circularly from broken bubbles occurs, so a force extended in length, breadth, or depth happens from these tubes or pistons. For every one of them is a tube to the preceding one and a piston to the following one.

Beyond what the state of the air allows, a circulation of aether follows, either as we have said, by being led out, or even by being pushed in from one side and led out from the other, just as happens in bows which are bent from concavity to convexity or vice versa. There, too, the effort of some fluid within the passages—already compressed on one side and dilated on the other—cannot fail to restore itself.

[Page 65]

To this also belong Glass Tears (Lacrymae vitri) and things similar to them from the most learned Johann Otto of Schaffhausen (who, with the most learned Heinrich Sereta, a companion in studies, recently illustrated those two most noble senses, sight and hearing).

These pertain to the observed filaments of glass; concerning which, although many hypotheses are extended, it is nevertheless certain that all can be reduced to the exhausted or distended—that is, the circulation of aether, which is our hypothesis.

Hobbes composes them from thin bows; Vossius says a vacuum or a quasi-vacuum is within; Honoratus Fabri prefers a certain tense spirit (like the little cord of Franciscus Linus); Huddenius and others prefer compression. Our hypothesis, with no small indication of truth, reconciles them all.

In a tense bow, there is compression on one side and distraction on the other; wherever air is drawn away, aether is collected. Therefore, when a hot Glass Tear is immersed in water and extinguished, the fire—which in every heated thing discusses and expels air—is conversely compressed by the water.

Or, what is the same thing, the fire being suddenly absorbed by the acid as if by an alkali, the aether—refilling the place—is drawn and collected into those bubbles and channels.

These pierce the whole glass with innumerable burrows, yet they all come together at the apex where the tear finally entered the water.

Whither the fire already receives itself from the beginning, just as when one end of an iron rod is glowing and extinguished, the other end grows hot. Therefore, all these burrows, by which the whole body of the glass is made porous as if by mines, are filled with aether…

[Page 66]

…as others might call it, they are full of vacuum or nothingness, just like exhausted glass, or like an aeolipile in which the air, rarefied and expelled by heat, leaves behind a great vacuum—that is, more than the fair share of collected aether—after the opening is blocked and it is cooled. Nothing is more consistent with this than the example of an aeolipile suddenly cooled and obstructed.

Therefore, when the apex is broken, or any other bubble communicating with the rest, the collected aether is seen to exit with great force and air enters; moreover, all the burrows, because they are so subtle and fragile, are ruptured.

Consequently, it is necessary for the glass to violently shatter into dust.

This is why:

• it becomes stronger when the cold is increased (as if buried in snow)
• the rupture becomes weaker if retracted by the heat of fire.

For the cold, which initially created the place (the sides of the glass vessels in this place contracting and diminishing), causes a sudden increase, therefore a vacuum in place of the air, therefore a collection of aether; and since the body is contracted, it increases the obstruction of the pores. When new fire fills the place, the aether is diminished, air is admitted, and the pores are opened. It is clear, therefore, that this miracle of nature is also owed to the Elater of Aether.

The motion of the blood, from which the rest of the animal functions proceed (for the heart owes its motion to the blood, not, as Descartes thought, the blood to the heart), must without doubt be sought from the reaction of a certain aerial nitre received through respiration. For it is credible that just as the sea is impregnated with salt, so the air is impregnated with a certain nitre…

[67]

…Once the air is drawn in, unless it is recently mixed, it is useless for a new draft; this is confirmed by Drebbel’s experiment, who prepared a certain essence of air which immediately provided a certain vivid refrigeration to air that was otherwise sluggish and unhealthy. Now, if vital motion is from reaction, it will be from the Elater, through the higher things, and therefore from the circulation of aether. It was said above that the motion of the Ocean in the earth is from the same cause, analogous to the circulation of blood in the body: the same is true of the motion of air, or wind.

Wind can be made by art from water dispersing itself by a fall; it is likewise credible that nature often does this in the caverns of mountains. Bellows create wind by compression; in the same way, clouds heavy with their descent strike the air between themselves and the earth. Any simple motion in the air makes wind because it strikes and compresses the air, and accordingly attracts other air to refill the place.

Fire makes wind, and any heat does so, because by rarefying everything it attracts something subtler, refilling the exhausted place, and that by the principle of the Elater so often inculcated.

Hence fire requires air, not for food (fuel), but to protect the place. From this, the winds within the Tropics immediately follow the sun; closed places, vaulted temples, and caverns attract air or wind in cold weather because they are warmer than the ambient air; in warm ambient weather, because they are then cold, they remit it. Hence the Winds of certain places and times are constant…

[Page 68]

…observations of [Poullet]. The sun does not properly attract vapors, and their ascent does not depend as much on the principle of the Elater as on gravity; for the reason that fire, smoke, vapor, or the “May dew” enclosed in an eggshell, and the sap in plants evoked by the sun, or anything sublimable or distillable ascends, is because they are so rarefied by the interposed aether that they become lighter than an equal space of air. However, the elastic force of displosion [explosion] in fire contributes most, so that when elevation is prohibited, as in distillation by descent, the heat nevertheless repels the distillable things from itself, but regularly pushes them upward because the heat or fire itself, being lighter than air, carries them away in its ascent.

If, therefore, the motion of the seas and winds, of vapors, the fermentation of blood, reactions, and restorations all proceed from the Elater, what more shall we add? For from this same principle, almost the whole of Music, a great part of the art of Ballistics, and a great part of the rest of mechanics can be sufficiently inferred to depend. Certainly, it is credible that nerves are nothing other than tense chords, whose violent pulling—the muscles on both sides being contracted—raises themselves and the limbs with them. Hence, for the explanation of sensation, there is no need to flee to some “nervous liquor,” since in a tense thing, a struck effort reaches from the beginning to the end, because the drawing apart pertains to every sensible point. And just as tense things move more slowly and are broken more easily when moistened, as the air within is thickened and accordingly less dilatable;

[Page 69]

…so the same thing happens in the nerves during sleep, so that sensation is, as it were, overwhelmed. Now, at every sensible point, and toward every sensible point, or in every sensible angle, and thus in a body continually tendible for sensation, if the causes of tension and friction are assumed, those many excellent Physico-Mathematical theorems can be demonstrated. These are ready for both the experimenter and the reasoner, and can unite into a certain new part of mixed Mathematics, which it will be permitted to call Elastica.

[These theorems concern] the decrease of motion, or the increase of power from a violent impulse of a thing; the increase of restoration relative to the inverse increase of the motion of heavy things; isochronous vibrations; restorations of the same even from different tensions being isochronous; the time and place of rupture; the proportion of elater to gravity; and the lines which a given point describes in restoration, specifically the tension of a straight line in a chord, a curve in a bow, a surface in a drum, and a solid in a vessel. These have been demonstrated or observed by most subtle men such as Galileo, Torricelli, Honoratus Fabri, Steno, Giovanni Alfonso Borelli, and others. And here one may admire the practice of God in the geometry of things. For even if by the nature of things it is impossible for any body to be entirely shining, transparent, fluid, heavy, soft, tendible, flexible, hard, hot, etc., or likewise for a motion to be continuous, uniform, and one…

[Page 70]

…uniformly accelerated or diminished, rectilinear, circular, reflected, refracted, or permuted, to be exact; for the effects of magnetism, light, and sound to reach every assignable point, and so forth.

It happens, however, that to our senses all these things appear to be so, even if they are not; and for our use, it is as if they were; and thus by the incredible benefit of God, Optics, Music, Elastic Statics, Pammachia (or the science of impetus and percussion), Myology (or the motion of muscles), even Pyrotechnics and Universal Mechanics, and whatever is mixed from Physico-Mathematical sciences, can be cultivated with theorems that do not fail the senses (except by accident) to the point of envy from the pure sciences. This could not be procured unless by an inimitable artifice directed toward the motions and structures of qualities and sensible motions causing them below every sensible point in the smallest parts, and in every sensible region.