THE COMETS
SHOOTING STARS, BOLIDES, URANOLITHS OR METEORIC STONES
What marvels have been reviewed by our dazzled eyes since the outset of
these discussions! We first surveyed the magnificent host of stars that
people the vast firmament of Heaven; next we admired and wondered at
suns very differently constituted from our own; then returning from the
depths of space, crossing at a bound the abyss that separates us from
these mysterious luminaries, the distant torches of our somber night,
terrible suns of infinity, we landed on our own beloved orb, the superb
and brilliant day-star. Thence we visited his celestial family, his
system, in which our Earth is a floating island. But the journey would
be incomplete if we omitted certain more or less vagabond orbs, that
occasionally approach the Sun and Earth, some of which may even collide
with us upon their celestial path. These are in the first place the
comets, then the shooting stars, the fire-balls, and meteorites.
Glittering, swift-footed heralds of Immensity, these comets with golden
wings glide lightly through Space, shedding a momentary illumination by
their presence. Whence come they? Whither are they bound?
What problems they propound to us, when, as in some beautiful display of
pyrotechnics, the arch of Heaven is illuminated with their fantastic
light!
But first of all--what is a Comet?
If instead of living in these days of the telescope, of spectrum
analysis, and of astral photography, we were anterior to Galileo, and to
the liberation of the human spirit by Astronomy, we should reply that
the comet is an object of terror, a dangerous menace that appears to
mortals in the purity of the immaculate Heavens, to announce the most
fatal misfortunes to the inhabitants of our planet. Is a comet visible
in the Heavens? The reigning prince may make his testament and prepare
to die. Another apparition in the firmament bodes war, famine, the
advent of grievous pestilence. The astrologers had an open field, and
their fertile imagination might hazard every possible conjecture, seeing
that misfortunes, great or small, are not altogether rare in this
sublunar world.
How many intellects, and those not the most vulgar, from antiquity to
the middle of the last century cursed the apparition of these hirsute
stars, which brought desolation to the heart of man, and poured their
fatal effluvia upon the head of poor Humanity. The history of the
superstitions and fears that they inspired of old would furnish matter
for the most thrilling of romances. But, on the other hand, the volume
would be little flattering to the common-sense of our ancestors. Despite
the respect we owe our forefathers, let us recall for a moment the
prejudices attaching to the most famous comets whose passage, as
observed from the Earth, has been preserved to us in history.
[Illustration: FIG. 49.--Great Comet of 1858.]
* * * * *
Without going back to the Deluge, we note that the Romans established a
relation between the Great Comet of 43 B.C. and the death of Caesar, who
had been assassinated a few months previously. It was, they asserted,
the soul of their great Captain, transported to Heaven to reign in the
empyrean after ruling here below. Were not the Emperors Lords of both
Earth and Heaven?
We must in justice recognize that certain more independent spirits
emancipated themselves from these superstitions, and we may cite the
reply of Vespasian to his friends, who were alarmed at the evil presage
of a flaming comet: "Fear nothing," he said, "this bearded star concerns
me not; rather should it threaten my neighbor the King of the Parthians,
since he is hairy and I am bald."
In the year 837 one of these mysterious visitants appeared in the
Heavens. It was in the reign of Lewis the Debonair. Directly the King
perceived the comet, he sent for an astrologer, and asked what he was to
conclude from the apparition. As the answers were unsatisfactory he
tried to avert the augury by prayers to Heaven, by ordaining a general
fast to all his Court, and by building churches. Notwithstanding, he
died three years later, and the historians profited by this slender
coincidence to set up a correlation between the fatal star and the death
of the Sovereign. This comet, famous in history, is no other than that
of Halley, in one of its appearances.
This comet returned to explore the realms near the Sun in 1066, at the
moment when William of Normandy was undertaking the Conquest of England,
and was misguided enough to go across and reign in London, instead of
staying at home and annexing England, thus by his action founding the
everlasting rivalry between France and this island. A beneficial
influence was attributed to the comet in the Battle of Hastings.
A few centuries later it again came into sight from the Earth, in 1456,
three years after the capture of Constantinople by the Turks. Feeling
ran high in Europe, and this celestial omen was taken for a proof of the
anger of the Almighty. The moment was decisive; the Christians had to be
rescued from a struggle in which they were being worsted. At this
conjuncture, Pope Calixtus resuscitated a prayer that had fallen into
disuse, the _Angelus_; and ordered that the bells of the churches should
be rung each day at noon, that the Faithful might join at the same hour
in prayer against the Turks and the Comet. This custom has lasted down
to our own day.
Again, to the comet of 1500 was attributed the tempest that caused the
death of Bartholomew Diaz, a celebrated Portuguese navigator, who
discovered the Cape of Good Hope.
In 1528 a bearded star of terrific aspect alarmed the world, and the
more serious spirits were influenced by this menacing comet, which
burned in the Heavens like "a great and gory sword." In a chapter on
Celestial Monsters the celebrated surgeon Ambroise Pare describes this
awful phenomenon in terms anything but seductive, or reassuring, showing
us the menacing sword surrounded by the heads it had cut off (Fig. 50).
[Illustration: FIG. 50.--What our Ancestors saw in a Comet.
_After Ambroise Pare (1528)._]
[Illustration: FIG. 51.--Prodigies seen in the Heavens by our
Forefathers.]
Omens of battle, 1547.
Deer and warriors, July 19, 1550.
Cavalry, and a bloody branch crossing the sun, June 11, 1554.]
Our fathers saw many other prodigies in the skies; their descendants,
less credulous, can study the facsimile reproduced in Fig. 51, of the
drawings published in the year 1557 by Conrad Lycosthenes in his curious
Book of Prodigies.
So, too, it is asserted that Charles V renounced the jurisdiction of his
Estates, which were so vast that "the Sun never slept upon them,"
because he was terrified by the comet of 1556 which burned in the skies
with an alarming brilliancy, into passing the rest of his days in prayer
and devotion.
It is certain that comets often exhibit very strange characteristics,
but the imagination that sees in them such dramatic figures must indeed
be lively. In the Middle Ages and the Renaissance these were swords of
fire, bloody crosses, flaming daggers, etc., all horrible objects ready
to destroy our poor human race!
At the time of the Romans, Pliny made some curious distinctions between
them: "The Bearded Ones let loose their hair like a majestic beard; the
Javelin darts forth like an arrow; if the tail is shorter and ends in a
point, it is called the Sword; this is the palest of all the Comets; it
shines like a sword, without rays; the Plate or Disk is named in
conformity with its figure; its color is amber, the Barrel is actually
shaped like a barrel, as it might be in smoke, with light streaming
through it; the Horn imitates the figure of a horn erected in the sky,
and the Lamp that of a burning flame; the Equine represents a horse's
mane, shaken violently with a circular motion. There are bristled
comets; these resemble the skins of beasts with the fur on them, and are
surrounded by a nebulosity. Lastly, the tails of certain comets have
been seen to menace the sky in the form of a lance."
These hairy orbs that appear in all directions, and whose trajectories
are sometimes actually perpendicular to the plane of the ecliptic,
appear to obey no regular law. Even in the seventeenth century the
perspicacious Kepler had not divined their true character, seeing in
them, like most of his contemporaries, emanations from the earth, a sort
of vapor, losing itself in space. These erratic orbs could not be
assimilated with the other members of our grand solar family where,
generally speaking, everything goes on in regular order.
And even in our own times, have we not seen the people terrified at the
sight of a flaming comet? Has not the end of the world by the agency of
comets been often enough predicted? These predictions are so to speak
periodic; they crop up each time that the return of these cosmical
formations is announced by the astronomers, and always meet with a
certain number of timid souls who are troubled as to our destinies.
* * * * *
To-day we know that these wanderers are subject to the general laws
that govern the universe. The great Newton announced that, like the
planets, they were obedient to universal attraction; that they must
follow an extremely elongated curve, and return periodically to the
focus of the ellipse. From the basis of these data Halley calculated the
progress of the comet of 1682, and ascertained that its motions
presented such similarity with the apparitions of 1531 and 1607, that he
believed himself justified in identifying them and in announcing its
return about the year 1759. Faithful to the call made upon it,
irresistibly attracted by the Orb of Day, the comet, at first pale, then
ardent and incandescent, returned at the date assigned to it by
calculation, three years after the death of the illustrious astronomer.
Shining upon his grave it bore witness to the might of human thought,
able to snatch the profoundest secrets from the Heavens!
This fine comet returns every seventy-six years, to be visible from the
Earth, and has already been seen twenty-four times by the astonished
eyes of man. It appears, however, to be diminishing in magnitude. Its
last appearance was in 1835, and we shall see it again in 1910, a little
sooner than its average period, the attraction of Jupiter having this
time slightly accelerated its course, while in 1759 it retarded it.
The comets thus follow a very elongated orbit, either elliptic, turning
round the Sun, or parabolic, dashing out into space. In the first case,
they are periodic (Fig. 52), and their return can be calculated. In the
second they surprise us unannounced, and return to the abysses of
eternity to reappear no more.
[Illustration: FIG. 52.--The orbit of a Periodic Comet.]
Their speed is even greater than that of the planets, it is equivalent
to this, multiplied by the square root of 2, that is to say by 1.414.
Thus at the distance of the Earth from the Sun this velocity = 29,500
meters (18 miles) per second, multiplied by the above number, that is,
41,700 meters (over 25 miles). At the distance of Mercury it = 47 x
1.414 or 66,400 meters (over 40 miles) per second.
Among the numerous comets observed, we do not as yet know more than some
twenty of which the orbit has been determined. Periodicity in these
bearded orbs is thus exceptional, if we think of the innumerable
multitude of comets that circle through the Heavens. Kepler did not
exaggerate when he said "there are as many comets in the skies as there
are fishes in the sea." These scouts of the sidereal world constitute a
regular army, and if we are only acquainted with the dazzling generals
clad in gold, it is because the more modest privates can only be
detected in the telescope. Long before the invention of the latter,
these wanderers in the firmament roamed through space as in our own day,
but they defied the human eye, too weak to detect them. Then they were
regarded as rare and terrible objects that no one dared to contemplate.
To-day they may be counted by hundreds. They have lost in prestige and
in originality; but science is the gainer, since she has thus endowed
the solar system with new members. No year passes without the
announcement of three or four new arrivals. But the fine apparitions
that attract general attention by their splendor are rare enough.
These eccentric visitors do not resemble the planets, for they have no
opaque body like the Earth, Venus, Mars, or any of the rest. They are
transparent nebulosities, of extreme lightness, without mass nor
density. We have just photographed the comet of the moment, July, 1903:
the smallest stars are visible through its tail, and even through the
nucleus.
They arrive in every direction from the depths of space, as though to
reanimate themselves in the burning, luminous, electric solar center.
Attracted by some potent charm toward this dazzling focus, they come
inquisitive and ardent, to warm themselves at its furnace. At first pale
and feeble, they are born again when the Sun caresses them with his
fervid heat. Their motions accelerate, they haste to plunge wholly into
the radiant light. At length they burst out luminous and superb, when
the day-star penetrates them with his burning splendor, illuminates them
with a marvelous radiance, and crowns them with glory. But the Sun is
generous. Having showered benefits upon these gorgeous celestial
butterflies that flutter round him as round some altar of the gods, he
grants them liberty to visit other heavens, to seek fresh universes....
The original parabola is converted into an ellipse, if the imprudent
adventurer in returning to the Sun passes near some great planet, such
as Jupiter, Saturn, Uranus, or Neptune, and suffers its attraction. It
is then imprisoned by our system, and can no longer escape from it.
After reenforcement at the solar focus, it must return to the identical
point at which it felt the first pangs of a new destiny. Henceforward,
it belongs to our celestial family, and circles in a closed curve.
Otherwise, it is free to continue its rapid course toward other suns and
other systems.
* * * * *
As a rule, the telescope shows three distinct parts in a comet. There is
first the more brilliant central point, or _nucleus_, surrounded by a
nebulosity called the _hair_, or _brush_, and prolonged in a luminous
appendix stretching out into the _tail_. The _head_ of the comet is the
brush and the nucleus combined.
[Illustration: FIG. 53.--The tails of Comets are opposed to the Sun.]
It is usually supposed that the tail of a comet follows it throughout
the course of its peregrinations. Nothing of the kind. The appendix may
even precede the nucleus; it is always opposite the Sun,--that is to
say, it is situated on the prolongation of a straight line, starting
from the Sun, and passing through the nucleus (Fig. 53). The tail does
not exist, so long as the comet is at a distance from the orb of day;
but in approaching the Sun, the nebulosity is heated and dilates, giving
birth to those mysterious tails and fantastic streamers whose
dimensions vary considerably for each comet. The dilations and
transformations undergone by the tail suggest that they may be due to a
repulsive force emanating from the Sun, an electric charge transmitted
doubtless through the ether. It is as though Phoebus blew upon them
with unprecedented force.
Telescopic comets are usually devoid of tail, even when they reach the
vicinity of the Sun. They appear as pale nebulosities, rounded or oval,
more condensed toward the center, without, however, showing any distinct
nucleus. These stars are only visible for a minute fraction of their
course, when they reach a point not far from the Sun and the terrestrial
orbit.
The finest comets of the last century were those of 1811, 1843, 1858,
1861, 1874, 1880, 1881, and 1882. The Great Comet of 1811, after
spreading terror over certain peoples, notably in Russia, became the
providence of the vine-growers. As the wine was particularly good and
abundant that year, the peasants attributed this happy result to the
influence of the celestial visitant.
In 1843 one of these strange messengers from the Infinite appeared in
our Heavens. It was so brilliant that it was visible in full daylight on
February 28th, alongside of the Sun. This splendid comet was
accompanied by a marvelous rectilinear tail measuring 300,000,000
kilometers (186,000,000 miles) in length, and its flight was so rapid
that it turned the solar hemisphere at perihelion in two hours,
representing a speed of 550 kilometers (342 miles) a second.
But the most curious fact is that this radiant apparition passed so near
the Sun that it must have traversed its flames, and yet emerged from
them safe and sound.
Noteworthy also was the comet of 1858 (Fig. 49), discovered at Florence
by Donati. Its tail extended to a length of 90,000,000 kilometers
(55,900,000 miles), and its nucleus had a diameter of at least 900
kilometers (559 miles). It is a curious coincidence that the wine was
remarkably excellent and abundant in that year also.
The comet of 1861 almost rivaled the preceding.
Coggia's Comet, in 1874, was also remarkable for its brilliancy, but was
very inferior to the last two. Finally, the latest worthy of mention
appeared in 1882. This magnificent comet also touched the Sun, traveling
at a speed of 480 kilometers (299 miles) per second. It crossed the
gaseous atmosphere of the orb of day, and then continued its course
through infinity. On the day of, and that following, its perihelion, it
could be detected with the unaided eye in full daylight, enthroned in
the Heavens beside the dazzling solar luminary. For the rest, it was
neither that of 1858 nor of 1861.
Since 1882 we have not been favored with a visit from any fine comet;
but we are prepared to give any such a reception worthy of their
magnificence: first, because now that we have fathomed them we are no
longer awestruck; second, because we would gladly study them more
closely.
* * * * *
In short, these hirsute stars, whose fantastic appearance impressed the
imagination of our ancestors so vividly, are no longer formidable. Their
mass is inconsiderable; they seem to consist mainly of the lightest of
gases. Analysis of their incandescence reveals a spectrum closely
resembling that of many nebulae; the presence of carbon is more
particularly obvious. Even the nucleus is not solid, and is often
transparent.
It is fair to say that the action of a comet might be deleterious if one
of these orbs were to arrive directly upon us. The transformation of
motion into heat, and the combination of the cometary gases with the
oxygen of our atmosphere might produce a conflagration, or a general
poisoning of the atmosphere.
But the collision of a comet with a planet is almost an impossibility.
This phenomenon could only occur if the comet crossed the planetary
orbit at the exact moment at which the planet was passing. When we
think of the immensity of space, of the extraordinary length of way
traversed by a world in its annual journey round the Sun, and the speed
of its rotation, we see why this coincidence is hardly likely to occur.
Thus, among the hundreds of comets catalogued, a few only cut the
terrestrial orbit. One of them, that of 1832, traversed the path of our
globe in the nights of October 29 and 30 in that year; but the Earth
only passed the same point thirty days later, and at the critical period
was more than 80,000,000 kilometers (50,000,000 miles) away from the
comet.
On June 30, 1861, however, the Earth passed through the extremity of the
tail of the Great Comet of that year. No one even noticed it. The
effects were doubtless quite immaterial.
In 1872 we were to collide with Biela's Comet, lost since 1852; now, as
we shall presently see, we came with flying colors out of that
disagreeable situation, because the comet had disintegrated, and was
reduced to powder. So we may sleep in peace as regards future danger
likely to come to us from comets. There is little fear of the
destruction of humanity by these windy bags.
These ethereal beauties whose blond locks float carelessly upon the
azure night are not concerned with us; they seem to have no other
preoccupation than to race from sun to sun, visiting new Heavens,
indifferent to the astonishment they produce in us. They speed
restlessly and tirelessly through infinity; they are the Amazons of
space.
What suns, what worlds must they have visited since the moment of their
birth! If these splendid fugitives could relate the story of their
wanderings, how gladly should we listen to the enchanting descriptions
of the various abodes they have journeyed to! But alas! these mysterious
explorers are dumb; they tell none of their secrets, and we must needs
respect their enigmatic silence.
Yet, some of them have left us a modest token of remembrance, an almost
impalpable nothing, sufficient, however, to enable us to address our
thanks to the considerate messenger.
* * * * *
Can there be any one upon the Earth who has not been struck by the
phosphorescent lights that glide through the somber night, leaving a
brilliant silver or golden track--the luminous, ephemeral trail of a
meteor?
Sometimes, when Night has silently spread the immensity of her wings
above the weary Earth, a shining speck is seen to detach itself in the
shades of evening from the starry vault, shooting lightly through the
constellations to lose itself in the infinitude of space.
[Illustration: FIG. 54.--A Meteor.]
These bewitching sparks attract our eyes and chain our senses.
Fascinating celestial fireflies, their dainty flames dart in every
direction through space, sowing the fine dust of their gilded wings upon
the fields of Heaven. They are born to die; their life is only a breath;
yet the impression which they make upon the imagination of mortals is of
the profoundest.
The young girl dreaming in the delicious tranquillity of the transparent
night smiles at this charming sister in the Heavens (Fig. 54). What can
not this adorable star announce to the tender and loving heart? Is it
the shy messenger of the happiness so long desired? Its unpremeditated
appearance fills the soul with a ray of hope and makes it tremble. It is
a golden beam that glides into the heart, expanding it in the thrills of
a sudden and ephemeral pleasure.... The radiant meteor seems to quit the
velvet of the deep blue sky to respond to the appeal of the imploring
voice that seeks its succor.
What secrets has it not surprised! And who bears malice against it? It
is the friend of the betrothed who invoke its passage to confide their
wishes, and associate it with their dreams. Tradition holds that if a
wish be formulated during the visible passage of a meteor it will
certainly be fulfilled before the year is out. Between ourselves,
however, this is but a surviving figment of the ancestral imagination,
for this celestial jewel takes no such active part in the doings of
Humanity.... Besides, try to express a wish distinctly in a second!
It is a curious fact that while comets have so often spread terror on
the Earth, shooting stars should on the contrary have been regarded with
benevolent feelings at all times. And what is a shooting star? These
dainty excursionists from the celestial shores are not, as is supposed,
true stars. They are atoms, nothings, minute fragments deriving in
general from the disintegration of comets. They come to us from a vast
distance, from millions on millions of miles, and circle in swarms
around the Sun, following a very elongated ellipse which closely
resembles that of the cometary orbit. Their flight is extremely rapid,
reaching sometimes more than 40 kilometers (25 miles) per second, a
cometary speed that is, as we have seen, greatly above that of our
terrestrial vehicle, which amounts to 29 to 30 kilometers (about 19
miles).
These little corpuscles are not intrinsically luminous; but when the
orbit of a swarm of meteors crosses our planet, a violent shock arises,
the speed of which may be as great as 72 kilometers (45 miles) in the
first second if we meet the star shower directly; the average rate,
however, does not exceed 30 to 40 kilometers (19 to 25 miles), for these
meteors nearly always cross our path obliquely. The height at which they
arrive is usually 110 kilometers (68 miles), and 80 kilometers (50
miles) at the moment of disappearance of the meteor; but shooting stars
have been observed at 300 kilometers (186 miles).
The friction caused by this collision high up in the atmosphere
transforms the motion into heat. The molecules incandesce, and burn like
true stars with a brilliancy that is often magnificent.
But their glory is of short duration. The excessive heat resulting from
the shock consumes the poor firefly; its remains evaporate, and drop
slowly to the Earth, where they are deposited on the surface of the soil
in a sort of ferruginous dust mixed with carbon and nickel. Some one
hundred and forty-six milliards of them reach us annually, as seen by
the unaided eye, and many more in the telescope; the effect of these
showers of meteoric matter is an insensible increase in the mass of our
globe, a slight lessening of its rotary motion, and the acceleration of
the lunar movements of revolution.
Although the appearance of shooting stars is a common enough phenomenon,
visible every night of the year, there are certain times when they
arrive in swarms, from different quarters of the sky. The most
remarkable dates in this connection are the night of August 10th and the
morning of November 14th. Every one knows the shooting stars of August
10th, because they arrive in the fine warm summer evenings so favorable
to general contemplation of the Heavens. The phenomenon lasts till the
12th, and even beyond, but the maximum is on the 10th. When the sky is
very clear, and there is no moon, hundreds of shooting stars can be
counted on those three nights, sometimes thousands. They all seem to
come from the same quarter of the Heavens, which is called the
_radiant_, and is situated for the August swarm in the constellation of
Perseus, whence they have received the name of _Perseids_. Our
forefathers also called them the tears of St. Lawrence, because the
feast of that saint is on the same date. These shooting stars describe a
very elongated ellipse, and their orbit has been identified with that of
the Great Comet of 1862.
The shower of incandescent asteroids on November 14th is often much more
abundant than the preceding. In 1799, 1833, and 1866, the meteors were
so numerous that they were described as showers of rain, especially on
the first two dates. For several hours the sky was furrowed with falling
stars. An English mariner, Andrew Ellicot, who made the drawing we
reproduce (Fig. 55), described the phenomenon as stupendous and alarming
(November 12, 1799, 3 A.M.). The same occurred on November 13, 1833. The
meteors that scarred the Heavens on that night were reckoned at 240,000.
These shooting stars received the name of _Leonids_, because their
radiant is situated in the constellation of the Lion.
[Illustration: FIG. 55.--Shooting Stars of November 12, 1799.
_From a contemporary drawing._]
This swarm follows the same orbit as the comet of 1866, which travels as
far as Uranus, and comes back to the vicinity of the Sun every
thirty-three years. Hence we were entitled to expect another splendid
apparition in 1899, but the expectations of the astronomers were
disappointed. All the preparations for the appropriate reception of
these celestial visitors failed to bring about the desired result. The
notes made in observatories, or in balloons, admitted of the
registration of only a very small number of meteors. The maximum was
thirteen. During that night, some 200 shooting stars were counted. There
were more in 1900, 1901, and, above all, in 1902. This swarm has become
displaced.
The night of November 27th again is visited by a number of shooting
stars that are the disaggregated remains of the Comet of Biela. This
comet, discovered by Biela in 1827, accomplished its revolution in six
and a half years, and down to 1846 it responded punctually to the
astronomers who expected its return as fixed by calculation. But on
January 13, 1846, the celestial wanderer broke in half: each fragment
went its own way, side by side, to return within sight from the Earth in
1852. It was their last appearance. That year the twin comets could
still be seen, though pale and insignificant. Soon they vanished into
the depths of night, and never appeared again. They were looked for in
vain, and were despaired of, when on November 27, 1872, instead of the
shattered comet, came a magnificent rain of shooting stars. They fell
through the Heavens, numerous as the flakes of a shower of snow.
The same phenomenon recurred on November 27, 1885, and confirmed the
hypothesis of the demolition and disaggregation of Biela's Comet into
shooting stars.
* * * * *
There is an immense variety in the brilliancy of the shooting stars,
from the weak telescopic sparks that vanish like a flash of lightning,
to the incandescent _bolides_ or _fire-balls_ that explode in the
atmosphere.
Fig. 56 shows an example of these, and it represents a fire-ball
observed at the Observatory of Juvisy on the night of August 10, 1899.
It arrived from Cassiopeia, and burst in Cepheus.
This phenomenon may occur by day as well as by night. It is often
accompanied by one or several explosions, the report of which is
sometimes perceptible to a considerable distance, and by a shower of
meteorites. The globe of fire bursts, and splits up into luminous
fragments, scattered in all directions. The different parts of the
fire-ball fall to the surface of the Earth, under the name of aerolites,
or rather of uranoliths, since they arrive from the depths of space, and
not from our atmosphere.
From the most ancient times we hear of showers of uranoliths to which
popular superstitions were attached; and the Greeks even gave the name
of _Sideros_ to iron, the first iron used having been sidereal.
[Illustration: FIG. 56.--Fire-Ball seen from the Observatory at Juvisy,
August 10, 1899.]
[Illustration: FIG. 57.--Explosion of a Fire-Ball above Madrid,
February 10, 1896.]
No year passes without the announcement of several showers of
uranoliths, and the phenomenon sometimes causes great alarm to those who
witness it. One of the most remarkable explosions is that which occurred
above Madrid, February 10, 1896, a fragment from which, sent me by M.
Arcimis, Director of the Meteorological Institute, fell immediately in
front of the National Museum (Fig. 57). The phenomenon occurred at 9.30
A.M., in brilliant sunshine. The flash of the explosion was so dazzling
that it even illuminated the interior of the houses; an alarming clap of
thunder was heard seventy seconds after, and it was believed that an
explosion of dynamite had occurred. The fire-ball burst at a height of
fourteen miles, and was seen as far as 435 miles from Madrid!
In one of Raphael's finest pictures (_The Madonna of Foligno_) a
fire-ball may be seen beneath a rainbow (Fig. 58), the painter wishing
to preserve the remembrance of it, as it fell near Milan, on September
4, 1511. This picture dates from 1512.
The dimensions of these meteorites vary considerably; they are of all
sizes, from the impalpable dust that floats in the air, to the enormous
blocks exposed in the Museum of Natural History in Paris. Many of them
weigh several million pounds. That represented below fell in Mexico
during the shower of meteors of November 27, 1885. It weighed about four
pounds.
[Illustration: FIG. 58.--Raphael's Fire-Ball (_The Madonna of
Foligno_).]
These bolides and uranoliths come to us from the depths of space; but
they do not appear to have the same origin as the shooting stars. They
may arise from worlds destroyed by explosion or shock, or even from
planetary volcanoes. The lightest of them may have been expelled from
the volcanoes of the Moon. Some of the most massive, in which iron
predominates, may even have issued from the bowels of the Earth,
projected into space by some volcanic explosion, at an epoch when our
globe was perpetually convulsed by cataclysms of extraordinary violence.
They return to us to-day after being removed from the Earth to distances
proportional to the initial speed imparted to them. This origin seems
the more admissible as the stones that fall from the skies exhibit a
mineral composition identical with that of the terrestrial materials.
[Illustration: FIG. 59.--A Uranolith.]
In any case, these uranoliths bring us back at least by their fall to
our Earth, and from henceforward we will remain upon it, to study its
position in space, and to take account of the place it fills in the
Universe, and of the astronomical laws that govern our destiny.