place wrestling instances, which we are also wont to call instances
of predominance. They are such as point out the predominance and
submission of powers compared with each other, and which of them is the
more energetic and superior, or more weak and inferior. For the motions
and effects of bodies are compounded, decomposed, and combined, no less
than the bodies themselves. We will exhibit, therefore, the principal
kinds of motions or active powers, in order that their comparative
strength, and thence a demonstration and definition of the instances in
question, may be rendered more clear.
Let the first motion be that of the resistance of matter, which exists
in every particle, and completely prevents its annihilation; so that
no conflagration, weight, pressure, violence, or length of time can
reduce even the smallest portion of matter to nothing, or prevent it
from being something, and occupying some space, and delivering itself
(whatever straits it be put to), by changing its form or place, or, if
that be impossible, remaining as it is; nor can it ever happen that it
should either be nothing or nowhere. This motion is designated by the
schools (which generally name and define everything by its effects and
inconveniences rather than by its inherent cause) by the axiom, that
two bodies cannot exist in the same place, or they call it a motion to
prevent the penetration of dimensions. It is useless to give examples
of this motion, since it exists in every body.
Let the second motion be that which we term the motion of connection,
by which bodies do not allow themselves to be separated at any point
from the contact of another body, delighting, as it were, in the
mutual connection and contact. This is called by the schools a motion
to prevent a vacuum. It takes place when water is drawn up by suction
or a syringe, the flesh by cupping, or when the water remains without
escaping from perforated jars, unless the mouth be opened to admit the
air, and innumerable instances of a like nature.
Let the third be that which we term the motion of liberty, by which
bodies strive to deliver themselves from any unnatural pressure or
tension, and to restore themselves to the dimensions suited to their
mass; and of which, also, there are innumerable examples. Thus, we have
examples of their escaping from pressure, in the water in swimming, in
the air in flying, in the water again in rowing, and in the air in the
undulation of the winds, and in springs of watches. An exact instance
of the motion of compressed air is seen in children’s popguns, which
they make by scooping out elder-branches or some such matter, and
forcing in a piece of some pulpy root or the like, at each end; then
they force the root or other pellet with a ramrod to the opposite end,
from which the lower pellet is emitted and projected with a report,
and that before it is touched by the other piece of root or pellet,
or by the ramrod. We have examples of their escape from tension, in
the motion of the air that remains in glass eggs after suction, in
strings, leather, and cloth, which recoil after tension, unless it be
long continued. The schools define this by the term of motion from the
form of the element; injudiciously enough, since this motion is to be
found not only in air, water, or fire, but in every species of solid,
as wood, iron, lead, cloth, parchment, etc., each of which has its own
proper size, and is with difficulty stretched to any other. Since,
however, this motion of liberty is the most obvious of all, and to be
seen in an infinite number of cases, it will be as well to distinguish
it correctly and clearly; for some most carelessly confound this with
the two others of resistance and connection; namely, the freedom from
pressure with the former, and that from tension with the latter, as if
bodies when compressed yielded or expanded to prevent a penetration of
dimensions, and when stretched rebounded and contracted themselves to
prevent a vacuum. But if the air, when compressed, could be brought to
the density of water, or wood to that of stone, there would be no need
of any penetration of dimensions, and yet the compression would be much
greater than they actually admit of. So if water could be expanded till
it became as rare as air, or stone as rare as wood, there would be no
need of a vacuum, and yet the expansion would be much greater than they
actually admit of.
We do not, therefore, arrive at a penetration of dimensions or a vacuum
before the extremes of condensation and rarefaction, while the motion
we speak of stops and exerts itself much within them, and is nothing
more than a desire of bodies to preserve their specific density (or,
if it be preferred, their form), and not to desert them suddenly, but
only to change by degrees, and of their own accord. It is, however,
much more necessary to intimate to mankind (because many other points
depend upon this), that the violent motion which we call mechanical,
and Democritus (who, in explaining his primary motions, is to be ranked
even below the middling class of philosophers) termed the motion of a
blow, is nothing else than this motion of liberty, namely, a tendency
to relaxation from compression. For in all simple impulsion or flight
through the air, the body is not displaced or moved in space, until its
parts are placed in an unnatural state, and compressed by the impelling
force. When that takes place, the different parts urging the other in
succession, the whole is moved, and that with a rotatory as well as
progressive motion, in order that the parts may, by this means also,
set themselves at liberty, or more readily submit. Let this suffice for
the motion in question.
Let the fourth be that which we term the motion of matter, and which
is opposed to the last; for in the motion of liberty, bodies abhor,
reject, and avoid, a new size or volume, or any new expansion or
contraction (for these different terms have the same meaning), and
strive, with all their power, to rebound and resume their former
density; on the contrary, in the motion of matter, they are anxious
to acquire a new volume or dimension, and attempt it willingly and
rapidly, and occasionally by a most vigorous effort, as in the example
of gunpowder. The most powerful, or at least most frequent, though not
the only instruments of this motion, are heat and cold. For instance,
the air, if expanded by tension (as by suction in the glass egg),
struggles anxiously to restore itself; but if heat be applied, it
strives, on the contrary, to dilate itself, and longs for a larger
volume, regularly passing and migrating into it, as into a new form (as
it is termed); nor after a certain degree of expansion is it anxious
to return, unless it be invited to do so by the application of cold,
which is not indeed a return, but a fresh change. So also water, when
confined by compression, resists, and wishes to become as it was
before, namely, more expanded; but if there happen an intense and
continued cold, it changes itself readily, and of its own accord, into
the condensed state of ice; and if the cold be long continued, without
any intervening warmth (as in grottoes and deep caves), it is changed
into crystal or similar matter, and never resumes its form.
Let the fifth be that which we term the motion of continuity. We do
not understand by this simple and primary continuity with any other
body (for that is the motion of connection), but the continuity of
a particular body in itself; for it is most certain that all bodies
abhor a solution of continuity, some more and some less, but all
partially. In hard bodies (such as steel and glass) the resistance to
an interruption of continuity is most powerful and efficacious, while
although in liquids it appears to be faint and languid, yet it is not
altogether null, but exists in the lowest degree, and shows itself in
many experiments, such as bubbles, the round form of drops, the thin
threads which drip from roofs, the cohesion of glutinous substances,
and the like. It is most conspicuous, however, if an attempt be made to
push this separation to still smaller particles. Thus, in mortars, the
pestle produces no effect after a certain degree of contusion, water
does not penetrate small fissures, and the air itself, notwithstanding
its subtilty, does not penetrate the pores of solid vessels at once,
but only by long-continued insinuation.
Let the sixth be that which we term the motion of acquisition, or the
motion of need.[151] It is that by which bodies placed among others
of a heterogeneous and, as it were, hostile nature, if they meet with
the means or opportunity of avoiding them, and uniting themselves with
others of a more analogous nature, even when these latter are not
closely allied to them, immediately seize and, as it were, select them,
and appear to consider it as something acquired (whence we derive the
name), and to have need of these latter bodies. For instance, gold, or
any other metal in leaf, does not like the neighborhood of air; if,
therefore, they meet with any tangible and thick substance (such as the
finger, paper, or the like), they immediately adhere to it, and are
not easily torn from it. Paper, too, and cloth, and the like, do not
agree with the air, which is inherent and mixed in their pores. They
readily, therefore, imbibe water or other liquids, and get rid of the
air. Sugar, or a sponge, dipped in water or wine, and though part of
it be out of the water or wine, and at some height above it, will yet
gradually absorb them.[152]
Hence an excellent rule is derived for the opening and dissolution of
bodies; for (not to mention corrosive and strong waters, which force
their way) if a body can be found which is more adapted, suited, and
friendly to a given solid, than that with which it is by some necessity
united, the given solid immediately opens and dissolves itself to
receive the former, and excludes or removes the latter.[153] Nor is the
effect or power of this motion confined to contact, for the electric
energy (of which Gilbert and others after him have told so many fables)
is only the energy excited in a body by gentle friction, and which does
not endure the air, but prefers some tangible substance if there be any
at hand.
Let the seventh be that which we term the motion of greater
congregation, by which bodies are borne toward masses of a similar
nature, for instance, heavy bodies toward the earth, light to the
sphere of heaven. The schools termed this natural motion, by a
superficial consideration of it, because produced by no external
visible agent, which made them consider it innate in the substances; or
perhaps because it does not cease, which is little to be wondered at,
since heaven and earth are always present, while the causes and sources
of many other motions are sometimes absent and sometimes present.
They therefore called this perpetual and proper, because it is never
interrupted, but instantly takes place when the others are interrupted,
and they called the others adscititious. The former, however, is in
reality weak and slow, since it yields, and is inferior to the others
as long as they act, unless the mass of the body be great; and although
this motion have so filled men’s minds, as almost to have obscured all
others, yet they know but little about it, and commit many errors in
its estimate.
Let the eighth be that which we term the motion of lesser congregation,
by which the homogeneous parts in any body separate themselves from
the heterogeneous and unite together, and whole bodies of a similar
substance coalesce and tend toward each other, and are sometimes
congregated, attracted, and meet, from some distance; thus in milk the
cream rises after a certain time, and in wine the dregs and tartar
sink; which effects are not to be attributed to gravity and levity
only, so as to account for the rising of some parts and the sinking
of others, but much more to the desire of the homogeneous bodies to
meet and unite. This motion differs from that of need in two points:
1st, because the latter is the stimulus of a malignant and contrary
nature, while in this of which we treat (if there be no impediment or
restraint), the parts are united by their affinity, although there be
no foreign nature to create a struggle; 2dly, because the union is
closer and more select. For in the other motion, bodies which have no
great affinity unite, if they can but avoid the hostile body, while in
this, substances which are connected by a decided kindred resemblance
come together and are molded into one. It is a motion existing in all
compound bodies, and would be readily seen in each, if it were not
confined and checked by the other affections and necessities of bodies
which disturb the union.
This motion is usually confined in the three following manners: by
the torpor of the bodies; by the power of the predominating body; by
external motion. With regard to the first, it is certain that there
is more or less sluggishness in tangible bodies, and an abhorrence of
locomotion; so that unless excited they prefer remaining contented with
their actual state, to placing themselves in a better position. There
are three means of breaking through this sluggishness--heat; the active
power of a similar body; vivid and powerful motion. With regard to
the first, heat is, on this account, defined as that which separates
heterogeneous, and draws together homogeneous substances; a definition
of the Peripatetics which is justly ridiculed by Gilbert, who says it
is as if one were to define man to be that which sows wheat and plants
vineyards; being only a definition deduced from effects, and those but
partial. But it is still more to be blamed, because those effects, such
as they are, are not a peculiar property of heat, but a mere accident
(for cold, as we shall afterward show, does the same), arising from
the desire of the homogeneous parts to unite; the heat then assists
them in breaking through that sluggishness which before restrained
their desire. With regard to the assistance derived from the power of
a similar body, it is most conspicuous in the magnet when armed with
steel, for it excites in the steel a power of adhering to steel, as a
homogeneous substance, the power of the magnet breaking through the
sluggishness of the steel. With regard to the assistance of motion,
it is seen in wooden arrows or points, which penetrate more deeply
into wood than if they were tipped with iron, from the similarity
of the substance, the swiftness of the motion breaking through the
sluggishness of the wood; of which two last experiments we have spoken
above in the aphorism on clandestine instances.[154]
The confinement of the motion of lesser congregation, which arises
from the power of the predominant body, is shown in the decomposition
of blood and urine by cold. For as long as these substances are filled
with the active spirit, which regulates and restrains each of their
component parts, as the predominant ruler of the whole, the several
different parts do not collect themselves separately on account of the
check; but as soon as that spirit has evaporated, or has been choked by
the cold, then the decomposed parts unite, according to their natural
desire. Hence it happens, that all bodies which contain a sharp spirit
(as salts and the like), last without decomposition, owing to the
permanent and durable power of the predominating and imperious spirit.
The confinement of the motion of lesser congregation, which arises from
external motion, is very evident in that agitation of bodies which
preserves them from putrefaction. For all putrefaction depends on the
congregation of the homogeneous parts, whence, by degrees, there ensues
a corruption of the first form (as it is called), and the generation of
another. For the decomposition of the original form, which is itself
the union of the homogeneous parts, precedes the putrefaction, which
prepares the way for the generation of another. This decomposition,
if not interrupted, is simple; but if there be various obstacles,
putrefactions ensue, which are the rudiments of a new generation. But
if (to come to our present point) a frequent agitation be excited by
external motion, the motion toward union (which is delicate and gentle,
and requires to be free from all external influence) is disturbed, and
ceases; which we perceive to be the case in innumerable instances.
Thus, the daily agitation or flowing of water prevents putrefaction;
winds prevent the air from being pestilent; corn turned about and
shaken in granaries continues clean: in short, everything which is
externally agitated will with difficulty rot internally.
We must not omit that union of the parts of bodies which is the
principal cause of induration and desiccation. When the spirit or
moisture, which has evaporated into spirit, has escaped from a porous
body (such as wood, bone, parchment, and the like), the thicker parts
are drawn together, and united with a greater effort, and induration
or desiccation is the consequence; and this we attribute not so much
to the motion of connection (in order to prevent a vacuum), as to this
motion of friendship and union.
Union from a distance is rare, and yet is to be met with in more
instances than are generally observed. We perceive it when one bubble
dissolves another, when medicines attract humors from a similarity of
substance, when one string moves another in unison with it on different
instruments, and the like. We are of opinion that this motion is very
prevalent also in animal spirits, but are quite ignorant of the fact.
It is, however, conspicuous in the magnet, and magnetized iron. While
speaking of the motions of the magnet, we must plainly distinguish
them, for there are four distinct powers or effects of the magnet which
should not be confounded, although the wonder and astonishment of
mankind has classed them together. 1. The attraction of the magnet to
the magnet, or of iron to the magnet, or of magnetized iron to iron.
2. Its polarity toward the north and south, and its variation. 3. Its
penetration through gold, glass, stone, and all other substances.
4. The communication of power from the mineral to iron, and from iron
to iron, without any communication of the substances. Here, however, we
only speak of the first. There is also a singular motion of attraction
between quicksilver and gold, so that the gold attracts quicksilver
even when made use of in ointment; and those who work surrounded by
the vapors of quicksilver, are wont to hold a piece of gold in their
mouths, to collect the exhalations, which would otherwise attack their
heads and bones, and this piece soon grows white.[155] Let this suffice
for the motion of lesser congregation.
Let the ninth be the magnetic motion, which, although of the nature of
that last mentioned, yet, when operating at great distances, and on
great masses, deserves a separate inquiry, especially if it neither
begin in contact, as most motions of congregation do, nor end by
bringing the substances into contact, as all do, but only raise them,
and make them swell without any further effect. For if the moon raise
the waters, or cause moist substances to swell, or if the starry
sphere attract the planets toward their apogees, or the sun confine
the planets Mercury and Venus to within a certain distance of his
mass;[156] these motions do not appear capable of being classed under
either of those of congregation, but to be, as it were, intermediately
and imperfectly congregative, and thus to form a distinct species.
Let the tenth motion be that of avoidance, or that which is opposed
to the motion of lesser congregation, by which bodies, with a kind of
antipathy, avoid and disperse, and separate themselves from, or refuse
to unite themselves with others of a hostile nature. For although this
may sometimes appear to be an accidental motion, necessarily attendant
upon that of the lesser congregation, because the homogeneous parts
cannot unite, unless the heterogeneous be first removed and excluded,
yet it is still to be classed separately,[157] and considered as a
distinct species, because, in many cases, the desire of avoidance
appears to be more marked than that of union.
It is very conspicuous in the excrements of animals, nor less, perhaps,
in objects odious to particular senses, especially the smell and
taste; for a fetid smell is rejected by the nose, so as to produce a
sympathetic motion of expulsion at the mouth of the stomach; a bitter
and rough taste is rejected by the palate or throat, so as to produce
a sympathetic concussion and shivering of the head. This motion is
visible also in other cases. Thus it is observed in some kinds of
antiperistasis, as in the middle region of the air, the cold of which
appears to be occasioned by the rejection of cold from the regions
of the heavenly bodies; and also in the heat and combustion observed
in subterranean spots, which appear to be owing to the rejection of
heat from the centre of the earth. For heat and cold, when in small
quantities, mutually destroy each other, while in larger quantities,
like armies equally matched, they remove and eject each other in
open conflict. It is said, also that cinnamon and other perfumes
retain their odor longer when placed near privies and foul places,
because they will not unite and mix with stinks. It is well known that
quicksilver, which would otherwise reunite into a complete mass, is
prevented from so doing by man’s spittle, pork lard, turpentine and
the like, from the little affinity of its parts with those substances,
so that when surrounded by them it draws itself back, and its
avoidance of these intervening obstacles is greater than its desire of
reuniting itself to its homogeneous parts; which is what they term the
mortification of quicksilver. Again, the difference in weight of oil
and water is not the only reason for their refusing to mix, but it is
also owing to the little affinity of the two; for spirits of wine,
which are lighter than oil, mix very well with water. A very remarkable
instance of the motion in question is seen in nitre, and crude bodies
of a like nature, which abhor flame, as may be observed in gunpowder,
quicksilver and gold. The avoidance of one pole of the magnet by iron
is not (as Gilbert has well observed), strictly speaking, an avoidance,
but a conformity, or attraction to a more convenient situation.