The Lives and Opinions of Eminent Philosophers
put themselves in opposition to facts, and lose sight of the bounds set
to human knowledge.
“The prognostics which are derived from the stars may, like those which
we borrow from animals, arise from a simple coincidence. They may also
have other causes, for example, some change in the air; for these two
suppositions both harmonize equally with facts; but it is impossible to
distinguish in what case one is to attribute them to the one cause or to
the other.
“The clouds may be formed either by the air condensed under the pressure
of the winds, or by the agency of atoms set apart for that end, or by
emanations from the earth and waters, or by other causes. For there are
a great number which are all equally able to produce this effect. When
the clouds clash with one another, or undergo any transformation, they
produce showers; and the long rains are caused by the motion of the
clouds when moved from places suitable to them through the air, when a
more violent inundation than usual takes place, from collections of some
masses calculated to produce these effects.
“Thunder possibly arises from the movement of the winds revolving in the
cavities of the clouds; of which we may see an image in vessels in our
own daily use. It may also arise from the noise of fire acted upon by the
wind in them, and from the tearings and ruptures of the clouds when they
have received a sort of crystaline consistency. In a word, experience
drawn from our senses, teaches us that all these phænomena, and that one
in particular, may be produced in many different manners.
“One may also assign different causes to the lightning; either the shock
and collision of the clouds produce a fiery appearance, which is followed
by lightning; or the lighting up of the clouds by the winds, produces
this luminous appearance; or the mutual pressure of the clouds, or that
of the wind against them, disengages the lightning. Or, one might say,
that the interception of the light diffused from the stars, arrested for
a time in the bosom of the clouds, is driven from them subsequently by
their own movements, and by those of the winds, and so escapes from their
sides; that the lightning is an extremely subtile light that evaporates
from the clouds; that the clouds which carry the thunder are collected
masses of fire; that the lightning arises from the motion of the fire,
or from the conflagration of the wind, in consequence of the rapidity
and continuousness of its motion. One may also attribute the luminous
appearance of lightning to the rupture of the clouds under the action of
the winds, or to the fall of inflammable atoms. Lastly, one may easily
find a number of other explanations, if one applies to sensible facts,
in order to search out the analogies which they present to the heavenly
phænomena.
“Lightning precedes thunder, either because it is produced at the same
moment that the wind falls on the cloud, while the noise is only heard
at the instant when the wind has penetrated into the bosom of the cloud;
or, perhaps, the two phænomena being simultaneous, the lightning arrives
among us more rapidly than the noise of the thunder-bolt, as is in fact
remarked in other cases when we see at a distance the clash of two
objects.
“The thunderbolt may be produced either by a violent condensation of
the winds, or by their rapid motion and conflagration. It may arise
from the fact of the winds meeting in places which are too dense, in
consequence of the accumulation of clouds, and then a portion of the
current detaches itself and proceeds towards the lower situations; or
else it may be caused by the fire which is contained in the bosom of the
clouds precipitating itself downwards. As one may suppose that an immense
quantity of fire being accumulated in the clouds dilates, violently
bursting the substance which envelops it, because the resistance of the
centre hinders it from proceeding further. This effect is especially
produced in the neighbourhood of high mountains; and, accordingly, they
are very frequently struck with the thunderbolts. In short, one may give
a number of explanations of the thunderbolt; but we ought, above all
things, to be on our guard against fables, and this one will easily be,
if one follows faithfully the sensible phænomena in the explanation of
these things, which are not perceived, except indirectly.
“Hurricanes (πρηστῆρες) may be caused either by the presence of a
cloud, which a violent wind sets in motion and precipitates with a
spiral movement towards the lower regions, or by a violent gust which
bears a cloud into the neighbourhood of some other current, or else by
the mere agitation of the wind by itself, when air is brought together
from the higher regions and compressed without being able to escape on
either side, in consequence of the resistance of the air which surrounds
it; when the hurricane descends towards the earth, then there result
whirlwinds in proportion to the rapidity of the wind that has produced
them; and this phænomenon extends over the sea also.
“Earthquakes may arise from the wind penetrating into the interior of the
earth, or from the earth itself receiving incessantly the addition of
exterior particles, and being in incessant motion as to its constituent
atoms, being in consequence disposed to a general vibration. That which
permits the wind to penetrate is the fact that falls take place in the
interior, or that the air being impressed by the winds insinuates itself
into the subterraneous caverns. The movement which numberless falls and
the re-action of the earth communicate to the earth, when this motion
meets bodies of greater resistance and solidity, is sufficient to explain
the earthquakes. One might, however, give an account of them in several
other ways.
“Winds are caused, either by the successive and regular addition of some
foreign matter, or else by the re-union of a great quantity of water; and
the differences of the winds may arise from the fact that some portions
of this same matter fall into the numerous cavities of the earth, and are
divided there.
“Hail is produced by an energetic condensation acting on the ethereal
particles which the cold embraces in every direction; or, in consequence
of a less violent condensation acting however on aqueous particles, and
accompanied by division, in such a manner as to produce, at the same
time, the re-union of certain elements and of the collective masses; or
by the rupture of some dense and compact mass which would explain at
the same time, the numerousness of the particles and their individual
hardness. As to the spherical form of the hail, one may easily account
for that by admitting that the shocks which it receives in every
direction make all the angles disappear, or else that at the moment when
the different fragments are formed, each of them is equally embraced on
all sides by aqueous or ethereal particles.
“Snow may be produced by a light vapour full of moisture which the clouds
allow to escape by passages intended for that end, when they are pressed,
in a corresponding manner, by other clouds, and set in motion by the
wind. Subsequently, these vapours become condensed in their progress
under the action of the cold which surrounds the clouds in the lower
regions. It may also be the case that this phænomenon is produced by
clouds of a slight density as they become condensed. In this case the
snow which escapes from the clouds would be the result of the contact, or
approximation of the aqueous particles, which in a still more condensed
state produce hail. This effect is most especially produced in the
air. Snow, again, may result from the collection of clouds previously
condensed and solidified; or from a whole army of other causes.
“Dew proceeds from a re-union of particles contained in the air
calculated to produce this moist substance. These particles may be
also brought from places which are moist or covered with water (for
in those places, above all others, it is that dew is abundant). These
then re-unite, again resume their aqueous form, and fall down. The same
phænomenon takes place in other cases before our own eyes under many
analogies.
“Hoar-frost is dew congealed by the influence of the cold air that
surrounds it.
“Ice is formed either by the detrition of round atoms contained in the
water, and the re-union at scalene and acute angles of the atoms which
exist in the water, or by an addition from without of these latter
particles, which penetrating into the water, solidify it by driving away
an equal amount of round atoms.
“The rainbow may be produced by the reflection of the solar rays on the
moist air; or it may arise from a particular property of light and air,
in virtue of which these particular appearances of colour are formed,
either because the shades which we perceive result directly from this
property, or because, on the contrary, it only produces one single shade,
which, reflecting itself on the nearest portions of the air, communicates
to them the tints which we observe. As to the circular form of the
rainbow, that depends either on the fact of the sight perceiving an equal
distance in every direction, or the fact of the atoms taking this form
when re-uniting in the air; or it may be caused by its detaching from the
air which moves towards the moon, certain atoms which, being re-united in
the clouds, give rise to this circular appearance.
“The lunar halo arises from the fact of the air, which moves towards the
moon from all quarters, uniformly intercepting the rays emitted by this
star, in such a way as to form around it a sort of circular cloud which
partially veils it. It may also arise from the fact of the moon uniformly
rejecting from all quarters, the air which surrounds it, in such a
manner as to produce this circular and opaque covering. And perhaps this
opaqueness may be caused by some particles which some current brings from
without; perhaps also, the heat communicates to the moon the property of
emitting by the pores in its surface, the particles by which this effect
is produced.
“Comets arise either from the fact, that in the circumstances already
stated, there are partial conflagrations in certain points of the heaven;
or, that at certain periods, the heaven has above our heads a particular
movement which causes them to appear. It may also be the case, that being
themselves endowed with a peculiar movement, they advance at the end of
certain periods of time, and in consequence of particular circumstances,
towards the places which we inhabit. The opposite reasons explain their
disappearance.
“Certain stars return to the same point in accomplishing their
revolutions; and this arises, not only as has been sometimes believed,
from the fact of the pole of the world, around which they move, being
immoveable, but also from the fact that the gyrations of the air which
surrounds them, hinder them from deviations like the wandering stars.
Perhaps also, this may be caused by the fact, that except in the route
in which they move, and in which we perceive them, they do not find any
material suitable to their nature. One may also explain this phænomenon
in many other manners, reasoning according to sensible facts; thus, it is
possible that certain stars may be wandering because that is the nature
of their movements, and, for the same reason, others may be immoveable.
It is also possible, that the same necessity which has originally given
them their circular movement, may have compelled some to follow their
orbit regularly, and have subjected others to an irregular progress; we
may also suppose that the uniform character of the centre which certain
stars traverse favour their regular march, and their return to a certain;
and that in the case of others, on the contrary, the differences of the