and particularly, whether the diurnal motion, by which the sun and
stars appear to us to rise and set, be a real motion of revolution in
the heavenly bodies, or only apparent in them, and real in the earth.
There may be an instance of the cross of the following nature. If there
be discovered any motion in the ocean from east to west, though very
languid and weak, and if the same motion be discovered rather more
swift in the air (particularly within the tropics, where it is more
perceptible from the circles being greater). If it be discovered also
in the low comets, and be already quick and powerful in them; if it
be found also in the planets, but so tempered and regulated as to be
slower in those nearest the earth, and quicker in those at the greatest
distance, being quickest of all in the heavens, then the diurnal motion
should certainly be considered as real in the heavens, and that of the
earth must be rejected; for it will be evident that the motion from
east to west is part of the system of the world and universal; since it
is most rapid in the height of the heavens, and gradually grows weaker,
till it stops and is extinguished in rest at the earth.
Again, let the required nature be that other motion of revolution,
so celebrated among astronomers, which is contrary to the diurnal,
namely, from west to east--and which the ancient astronomers assign
to the planets, and even to the starry sphere, but Copernicus and his
followers to the earth also--and let it be examined whether any such
motion be found in nature, or it be rather a fiction and hypothesis
for abridging and facilitating calculation, and for promoting that
fine notion of effecting the heavenly motions by perfect circles; for
there is nothing which proves such a motion in heavenly objects to be
true and real, either in a planet’s not returning in its diurnal motion
to the same point of the starry sphere, or in the pole of the zodiac
being different from that of the world, which two circumstances have
occasioned this notion. For the first phenomenon is well accounted for
by the spheres overtaking or falling behind each other, and the second
by spiral lines; so that the inaccuracy of the return and declination
to the tropics may be rather modifications of the one diurnal motion
than contrary motions, or about different poles. And it is most
certain, if we consider ourselves for a moment as part of the vulgar
(setting aside the fictions of astronomers and the school, who are
wont undeservedly to attack the senses in many respects, and to affect
obscurity), that the apparent motion is such as we have said, a model
of which we have sometimes caused to be represented by wires in a sort
of a machine.
We may take the following instances of the cross upon this subject. If
it be found in any history worthy of credit, that there has existed any
comet, high or low, which has not revolved in manifest harmony (however
irregularly) with the diurnal motion, then we may decide so far as to
allow such a motion to be possible in nature. But if nothing of the
sort be found, it must be suspected, and recourse must be had to other
instances of the cross.
Again, let the required nature be weight or gravity. Heavy and
ponderous bodies must, either of their own nature, tend toward the
centre of the earth by their peculiar formation, or must be attracted
and hurried by the corporeal mass of the earth itself, as being an
assemblage of similar bodies, and be drawn to it by sympathy. But if
the latter be the cause, it follows that the nearer bodies approach to
the earth, the more powerfully and rapidly they must be borne toward
it, and the further they are distant, the more faintly and slowly (as
is the case in magnetic attractions), and that this must happen within
a given distance; so that if they be separated at such a distance from
the earth that the power of the earth cannot act upon them, they will
remain suspended like the earth, and not fall at all.[130]
The following instance of the cross may be adopted. Take a clock moved
by leaden weights,[131] and another by a spring, and let them be set
well together, so that one be neither quicker nor slower than the
other; then let the clock moved by weights be placed on the top of
a very high church, and the other be kept below, and let it be well
observed, if the former move slower than it did, from the diminished
power of the weights. Let the same experiment be made at the bottom
of mines worked to a considerable depth, in order to see whether the
clock move more quickly from the increased power of the weights. But
if this power be found to diminish at a height, and to increase in
subterraneous places, the attraction of the corporeal mass of the earth
may be taken as the cause of weight.
Again, let the required nature be the polarity of the steel needle when
touched with the magnet. We have these two ways with regard to this
nature--Either the touch of the magnet must communicate polarity to
the steel toward the north and south, or else it may only excite and
prepare it, while the actual motion is occasioned by the presence of
the earth, which Gilbert considers to be the case, and endeavors to
prove with so much labor. The particulars he has inquired into with
such ingenious zeal amount to this--1. An iron bolt placed for a long
time toward the north and south acquires polarity from this habit,
without the touch of the magnet, as if the earth itself operating
but weakly from its distance (for the surface or outer crust of the
earth does not, in his opinion, possess the magnetic power), yet, by
long continued motion, could supply the place of the magnet, excite
the iron, and convert and change it when excited. 2. Iron, at a red
or white heat, when quenched in a direction parallel to the north
and south, also acquires polarity without the touch of the magnet, as
if the parts of iron being put in motion by ignition, and afterward
recovering themselves, were, at the moment of being quenched, more
susceptible and sensitive of the power emanating from the earth, than
at other times, and therefore as it were excited. But these points,
though well observed, do not completely prove his assertion.
An instance of the cross on this point might be as follows: Let a small
magnetic globe be taken, and its poles marked, and placed toward the
east and west, not toward the north and south, and let it continue
thus. Then let an untouched needle be placed over it, and suffered
to remain so for six or seven days. Now, the needle (for this is not
disputed), while it remains over the magnet, will leave the poles of
the world and turn to those of the magnet, and therefore, as long as it
remains in the above position, will turn to the east and west. But if
the needle, when removed from the magnet and placed upon a pivot, be
found immediately to turn to the north and south, or even by degrees
to return thither, then the presence of the earth must be considered
as the cause, but if it remains turned as at first, toward the east
and west, or lose its polarity, then that cause must be suspected, and
further inquiry made.
Again, let the required nature be the corporeal substance of the
moon, whether it be rare, fiery, and aërial (as most of the ancient
philosophers have thought), or solid and dense (as Gilbert and many
of the moderns, with some of the ancients, hold).[132] The reasons
for this latter opinion are grounded chiefly upon this, that the
moon reflects the sun’s rays, and that light does not appear capable
of being reflected except by solids. The instances of the cross will
therefore (if any) be such as to exhibit reflection by a rare body,
such as flame, if it be but sufficiently dense. Now, certainly, one
of the reasons of twilight is the reflection[133] of the rays of the
sun by the upper part of the atmosphere. We see the sun’s rays also
reflected on fine evenings by streaks of moist clouds, with a splendor
not less, but perhaps more bright and glorious than that reflected
from the body of the moon, and yet it is not clear that those clouds
have formed into a dense body of water. We see, also, that the dark
air behind the windows at night reflects the light of a candle in the
same manner as a dense body would do.[134] The experiment should also
be made of causing the sun’s rays to fall through a hole upon some dark
and bluish flame. The unconfined rays of the sun, when falling on faint
flames, do certainly appear to deaden them, and render them more like
white smoke than flames. These are the only instances which occur at
present of the nature of those of the cross, and better perhaps can
be found. But it must always be observed that reflection is not to
be expected from flame, unless it be of some depth, for otherwise it
becomes nearly transparent. This at least may be considered certain,
that light is always either received and transmitted or reflected by an
even surface.
Again, let the required nature be the motion of projectiles (such
as darts, arrows, and balls) through the air. The school, in its
usual manner, treats this very carelessly, considering it enough to
distinguish it by the name of violent motion, from that which they
term natural, and as far as regards the first percussion or impulse,
satisfies itself by its axiom, that two bodies cannot exist in one
place, or there would be a penetration of dimensions. With regard to
this nature we have these two crossways--The motion must arise either
from the air carrying the projected body, and collecting behind it,
like a stream behind boats, or the wind behind straws; or from the
parts of the body itself not supporting the impression, but pushing
themselves forward in succession to ease it. Fracastorius, and nearly
all those who have entered into any refined inquiry upon the subject,
adopt the first. Nor can it be doubted that the air has some effect,
yet the other motion is without doubt real, as is clear from a vast
number of experiments. Among others we may take this instance of the
cross, namely, that a thin plate or wire of iron rather stiff, or even
a reed or pen split in two, when drawn up and bent between the finger
and thumb, will leap forward; for it is clear that this cannot be
attributed to the air’s being collected behind the body, because the
source of motion is in the centre of the plate or pen, and not in its
extremities.
Again, let the required nature be the rapid and powerful motion of the
explosion of gunpowder, by which such vast masses are upheaved, and
such weights discharged as we observe in large mines and mortars, there
are two crossways before us with regard to this nature. This motion
is excited either by the mere effort of the body expanding itself when
inflamed, or by the assisting effort of the crude spirit, which escapes
rapidly from fire, and bursts violently from the surrounding flame as
from a prison. The school, however, and common opinion only consider
the first effort; for men think that they are great philosophers when
they assert that flame, from the form of the element, is endowed with
a kind of necessity of occupying a greater space than the same body
had occupied when in the form of powder, and that thence proceeds the
motion in question. In the meantime they do not observe, that although
this may be true, on the supposition of flame being generated, yet the
generation may be impeded by a weight of sufficient force to compress
and suffocate it, so that no such necessity exists as they assert. They
are right, indeed, in imagining that the expansion and the consequent
emission or removal of the opposing body, is necessary if flame be once
generated, but such a necessity is avoided if the solid opposing mass
suppress the flame before it be generated; and we in fact see that
flame, especially at the moment of its generation, is mild and gentle,
and requires a hollow space where it can play and try its force. The
great violence of the effect, therefore, cannot be attributed to this
cause; but the truth is, that the generation of these exploding flames
and fiery blasts arises from the conflict of two bodies of a decidedly
opposite nature--the one very inflammable, as is the sulphur, the
other having an antipathy to flame, namely, the crude spirit of the
nitre; so that an extraordinary conflict takes place while the sulphur
is becoming inflamed as far as it can (for the third body, the willow
charcoal, merely incorporates and conveniently unites the two others),
and the spirit of nitre is escaping, as far also as it can, and at
the same time expanding itself (for air, and all crude substances,
and water are expanded by heat), fanning thus, in every direction,
the flame of the sulphur by its escape and violence, just as if by
invisible bellows.
Two kinds of instances of the cross might here be used--the one of
very inflammable substances, such as sulphur and camphor, naphtha and
the like, and their compounds, which take fire more readily and easily
than gunpowder if left to themselves (and this shows that the effort
to catch fire does not of itself produce such a prodigious effect);
the other of substances which avoid and repel flame, such as all
salts; for we see that when they are cast into the fire, the aqueous
spirit escapes with a crackling noise before flame is produced, which
also happens in a less degree in stiff leaves, from the escape of
the aqueous part before the oily part has caught fire. This is more
particularly observed in quicksilver, which is not improperly called
mineral water, and which, without any inflammation, nearly equals the
force of gunpowder by simple explosion and expansion, and is said, when
mixed with gunpowder, to increase its force.
Again, let the required nature be the transitory nature of flame and
its momentaneous extinction; for to us the nature of flame does not
appear to be fixed or settled, but to be generated from moment to
moment, and to be every instant extinguished; it being clear that
those flames which continue and last, do not owe their continuance to
the same mass of flame, but to a continued succession of new flame
regularly generated, and that the same identical flame does not
continue. This is easily shown by removing the food or source of the
flame, when it at once goes out. We have the two following crossways
with regard to this nature:
This momentary nature either arises from the cessation of the cause
which first produced it, as in light, sounds, and violent motions,
as they are termed, or flame may be capable, by its own nature, of
duration, but is subjected to some violence from the contrary natures
which surround it, and is destroyed.
We may therefore adopt the following instance of the cross. We see
to what a height the flames rise in great conflagrations; for as the
base of the flame becomes more extensive, its vertex is more lofty.
It appears, then, that the commencement of the extinction takes place
at the sides, where the flame is compressed by the air, and is ill
at ease; but the centre of the flame, which is untouched by the air
and surrounded by flame, continues the same, and is not extinguished
until compressed by degrees by the air attacking it from the sides.
All flame, therefore, is pyramidal, having its base near the source,
and its vertex pointed from its being resisted by the air, and not
supplied from the source. On the contrary, the smoke, which is narrow
at the base, expands in its ascent, and resembles an inverted pyramid,
because the air admits the smoke, but compresses the flame; for let
no one dream that the lighted flame is air, since they are clearly
heterogeneous.
The instance of the cross will be more accurate, if the experiment can
be made by flames of different colors. Take, therefore, a small metal
sconce, and place a lighted taper in it, then put it in a basin, and
pour a small quantity of spirits of wine round the sconce, so as not to
reach its edge, and light the spirit. Now the flame of the spirit will
be blue, and that of the taper yellow; observe, therefore, whether the
latter (which can easily be distinguished from the former by its color,
for flames do not mix immediately, as liquids do) continue pyramidal,
or tend more to a globular figure, since there is nothing to destroy or
compress it. If the latter result be observed, it must be considered
as settled, that flame continues positively the same, while inclosed
within another flame, and not exposed to the resisting force of the air.
Let this suffice for the instances of the cross. We have dwelt the
longer upon them in order gradually to teach and accustom mankind to
judge of nature by these instances, and enlightening experiments, and
not by probable reasons.[135]
XXXVII. We will treat of the instances of divorce as the fifteenth of
our prerogative instances. They indicate the separation of natures of
the most common occurrence. They differ, however, from those subjoined
to the accompanying instances; for the instances of divorce point out
the separation of a particular nature from some concrete substance with
which it is usually found in conjunction, while the hostile instances
point out the total separation of one nature from another. They differ,
also, from the instances of the cross, because they decide nothing, but
only inform us that the one nature is capable of being separated from
the other. They are of use in exposing false forms, and dissipating
hasty theories derived from obvious facts; so that they add ballast and
weight, as it were, to the understanding.
For instance, let the acquired natures be those four which Telesius
terms associates, and of the same family, namely, heat, light, rarity,
and mobility, or promptitude to motion; yet many instances of divorce
can be discovered between them. Air is rare and easily moved, but
neither hot nor light; the moon is light but not hot; boiling water is
warm but not light; the motion of the needle in the compass is swift
and active, and yet its substance is cold, dense, and opaque; and there
are many similar examples.
Again, let the required natures be corporeal nature and natural action.
The latter appears incapable of subsisting without some body, yet may
we, perhaps, even here find an instance of divorce, as in the magnetic
motion, which draws the iron to the magnet, and heavy bodies to the
globe of the earth; to which we may add other actions which operate at
a distance. For such action takes place in time, by distinct moments,
not in an instant; and in space, by regular degrees and distances.
There is, therefore, some one moment of time and some interval of
space, in which the power or action is suspended between the two bodies
creating the motion. Our consideration, then, is reduced to this,
whether the bodies which are the extremes of motion prepare or alter
the intermediate bodies, so that the power advances from one extreme
to the other by succession and actual contact, and in the meantime
exists in some intermediate body; or whether there exists in reality
nothing but the bodies, the power, and the space? In the case of the
rays of light, sounds, and heat, and some other objects which operate
at a distance, it is indeed probable that the intermediate bodies
are prepared and altered, the more so because a qualified medium is
required for their operation. But the magnetic or attractive power
admits of an indifferent medium, and it is not impeded in any. But
if that power or action is independent of the intermediate body, it
follows that it is a natural power or action existing in a certain time
and space without any body, since it exists neither in the extreme nor
in the intermediate bodies. Hence the magnetic action may be taken as
an instance of divorce of corporeal nature and natural action; to which
we may add, as a corollary and an advantage not to be neglected, that
it may be taken as a proof of essence and substance being separate and
incorporeal, even by those who philosophize according to the senses.
For if natural power and action emanating from a body can exist at any
time and place entirely without any body, it is nearly a proof that
it can also emanate originally from an incorporeal substance; for a
corporeal nature appears to be no less necessary for supporting and
conveying, than for exciting or generating natural action.
XXXVIII. Next follow five classes of instances which we are wont to
call by the general term of instances of the lamp, or of immediate
information. They are such as assist the senses; for since every
interpretation of nature sets out from the senses, and leads, by a
regular fixed and well-established road, from the perceptions of
the senses to those of the understanding (which are true notions
and axioms), it necessarily follows, that in proportion as the
representatives or ministerings of the senses are more abundant and
accurate, everything else must be more easy and successful.
The first of these five sets of instances of the lamp, strengthen,
enlarge, and correct the immediate operations of the senses; the second
reduce to the sphere of the senses such matters as are beyond it; the
third indicate the continued process or series of such things and
motions, as for the most part are only observed in their termination,
or in periods; the fourth supply the absolute wants of the senses; the
fifth excite their attention and observation, and at the same time
limit the subtilty of things. We will now proceed to speak of them
singly.
XXXIX. In the sixteenth rank, then, of prerogative instances, we will
place the instances of the door or gate, by which name we designate
such as assist the immediate action of the senses. It is obvious,
that sight holds the first rank among the senses, with regard to
information, for which reason we must seek principally helps for that
sense. These helps appear to be threefold, either to enable it to
perceive objects not naturally seen, or to see them from a greater
distance, or to see them more accurately and distinctly.
We have an example of the first (not to speak of spectacles and the
like, which only correct and remove the infirmity of a deficient
sight, and therefore give no further information) in the lately
invented microscopes, which exhibit the latent and invisible minutiæ
of substances, and their hidden formation and motion, by wonderfully
increasing their apparent magnitude. By their assistance we behold
with astonishment the accurate form and outline of a flea, moss, and
animalculæ, as well as their previously invisible color and motion.
It is said, also, that an apparently straight line, drawn with a
pen or pencil, is discovered by such a microscope to be very uneven
and curved, because neither the motion of the hand, when assisted
by a ruler, nor the impression of ink or color, are really regular,
although the irregularities are so minute as not to be perceptible
without the assistance of the microscope. Men have (as is usual in
new and wonderful discoveries) added a superstitious remark, that
the microscope sheds a lustre on the works of nature, and dishonor
on those of art, which only means that the tissue of nature is much
more delicate than that of art. For the microscope is only of use for
minute objects, and Democritus, perhaps, if he had seen it, would have
exulted in the thought of a means being discovered for seeing his atom,
which he affirmed to be entirely invisible. But the inadequacy of these
microscopes, for the observation of any but the most minute bodies, and
even of those if parts of a larger body, destroys their utility; for
if the invention could be extended to greater bodies, or the minute
parts of greater bodies, so that a piece of cloth would appear like a
net, and the latent minutiæ and irregularities of gems, liquids, urine,
blood, wounds, and many other things could be rendered visible, the
greatest advantage would, without doubt, be derived.