insects appear to have over the luminosity of the phosphorescent
organs, exhibiting and withdrawing the light at will. It is not
necessary to suppose that this is an immediate effect, a conversion of
nerve force into light, and a withdrawal of that force. The action of
the creature's will may be merely in maintaining or destroying the
conditions under which the light is manifested. It may, for example,
have the power of withdrawing the supply of oxygen, and this
supposition receives some countenance from the observation cited from
Kirby and Spence on the two captured glow-worms, one of which
withdrew its light, while the other kept it shining, but while doing
so had the posterior extremity of the abdomen in constant motion. But
the animal may also have the power in another way of affecting the
chemical conditions of the phenomenon. It may, for example, have the
power of increasing or diminishing by some nervous influence the
supply of the necessary alkaline ingredient.
But if animal phosphorescence is really due to a process of slow
oxidation, there is one singular circumstance to be noted in
connection with it. Oxidation is a process that is normally
accompanied by the development of heat. Even where no light is
produced an increase of temperature regularly takes place when
substances are oxidized. We ought, then, to expect such a rise of
temperature when light is emitted by the phosphorescent organs of
animals. But the most careful observations have shown that nothing of
the kind can be detected. It was with a view to test this that Panceri
dissected out the luminous organs of so many specimens of Pholas. He
selected this mollusk because it was so abundant in the neighborhood
of Naples, where, his experiments were made; and in making his
experiments he made use of a thermopile, an apparatus by which, with
the aid of electricity, much smaller quantities of heat can be
indicated than by means of the most delicate thermometer. The organs
remained luminous long after they were extracted, but no rise in
temperature whatever could be found to accompany the luminosity. Many
experiments upon different animals were made with similar negative
results by means of the thermometer.
The only explanation of this that can be given is probably to be found
in the fact that the chemical process ascertained to go on in the
phosphorescence of organic compounds on which experiments were made in
the laboratory is an extremely slow one.
The so-called phosphorescence of most inorganic bodies is one of a
totally different nature from that exhibited in organic forms. The
diamond shines for a time in the dark after it has been exposed to the
sun; so do pieces of quartz when rubbed together, and powdered
fluor-spar when heated shines with considerable brilliancy. Various
artificial compounds, such as sulphide of calcium (Canton's
phosphorus, as it is called from the discoverer), sulphate of barium
(Bologna stone, or Bologna phosphorus), sulphide of strontium, etc.,
after being illuminated by the rays of the sun, give out in the dark a
beautiful phosphorescence, green, blue, violet, orange, red, according
to circumstances. The luminous paint which has recently attracted so
much attention is of the same nature. In these cases what we have is
either a conversion of heat rays into light rays (as in the powdered
fluor-spar), or the absorption and giving out again of sun-rays. In
the latter case the phenomenon is essentially the same as
fluorescence, in which the dark rays of the solar spectrum beyond the
violet are made visible.
But we must now return to the other questions that have been started
in relation to phosphorescence in animals. There has been much
speculation as to the object of this light, and to the purposes it
serves in Nature. Probably no general answer can be given to this
question. It is no doubt impossible to show why so many animals have
been endowed with this remarkable property; but we may consider some
of the effects which the possession of it has in different cases.
In the first place, it will undoubtedly serve in many cases to afford
light to enable the animal to see by, and in the Lampyridæ it would
seem that the degree of luminosity is related to the development of
the vision. In that family, according to the Rev. H.S. Gorham, the
eyes are developed, as a rule, in inverse proportion to the
luminosity. Where there is an ample supply of this kind of light the
eyes are small, but where the light is insignificant the eyes are
large by way of compensation. And moreover, where both eyes and light
are small, then the antennae are large and feathery, so that the
deficiency in the sense of sight is made up for by an unusual
development in the organs of touch.
But it is none the less certain that the presence of this light cannot
always be designed to serve this purpose, for many of the animals so
endowed are blind. The phosphorescent centipedes are without eyes,
like all the other members of the genus (_Geophilus_) to which they
belong, and probably the majority of phosphorescent marine forms are
likewise destitute of organs of sight.
Another suggestion is that the light derived from these marine forms,
and especially from deep-sea Alcyonarians, is what enables the members
of the deep-sea fauna that are possessed of eyes (which are always
enormously enlarged) to see. Such is the suggestion of Dr. Carpenter,
Sir Wyville Thomson, and Mr. Gwyn Jeffries; and it is possible that
this actually is one of the effects of the phosphorescent property.
But if so, it remains to inquire how the forms endowed with it came
to be possessed of a power useful in that way to other forms, but not
to themselves. According to the Darwinian doctrine of development, the
powers that are developed in different organisms by the process of
natural selection are such as are useful to themselves and not to
others, unless incidentally.
This consideration has led to another suggestion, namely, that the
property of phosphorescence serves as a protection to the forms
possessing it, driving away enemies in one way or another: it may be
by warning them of the fact that they are unpalatable food, as is
believed to be the case with the colors of certain brilliantly-colored
caterpillars; it may be in other ways. In Kirby and Spence one case is
recorded in which the phosphorescence of the common phosphorescent
centipede (_Geophilus electricus_) was actually seen apparently to
serve as a means of defence against an enemy. "Mr. Shepherd," says
that authority, "once noticed a scarabeus running round the
last-mentioned insect when shining, as if wishing, but afraid to
attack it." In the case of the jelly-fishes, it has been pointed out
that their well-known urticating or stinging powers would make them at
least unpleasant, if not dangerous, food for fishes; and that
consequently the luminosity by which so many of them are characterized
at night may serve at once as a warning to predatory fishes and as a
protection to themselves. The experience of the unpleasant properties
of many phosphorescent animals may likewise have taught fishes to
avoid all forms possessing this attribute, even though many of them
might be quite harmless.
Lastly, it has been suggested that the phosphorescence in the female
glow-worm may be designed to attract the male; and that it will
actually have this effect may readily be taken for granted.
Observation shows that the male glow-worm is very apt to be attracted
by a light. Gilbert White of Selborne mentions that they, attracted by
the light of the candles, came into his parlor. Another observer
states that by the same light he captured as many as forty male
glow-worms in one night.
[Illustration]
COMETS
(FROM MARVELS OF THE HEAVENS.)
BY CAMILLE FLAMMARION.
"Je viens vous annoncer une grande nouvelle:
Nous l'avons, en dormant, madame, échappé belle.
Un monde près de nous a passé tout du long,
Est chu tout au travers de notre tourbillon;
Et s'il eût en chemin rencontré notre terre,
Elle eût été brisée en morceaux comme verre."
MOLIÈRE.
[Illustration]
This announcement of Trissontin's to Philaminte, who begins the parody
on the fears caused by the appearance of comets, would not have been a
parody four or five centuries ago. These tailed bodies, which suddenly
come to light up the heavens, were for long regarded with terror, like
so many warning signs of divine wrath. Men have always thought
themselves much more important than they really are in the universal
order; they have had the vanity to pretend that the whole creation was
made for them, whilst in reality the whole creation does not suspect
their existence. The Earth we inhabit is only one of the smallest
worlds; and therefore it can scarcely be for it alone that all the
wonders of the heavens, of which the immense majority remains hidden
from it, were created. In this disposition of man to see in himself
the centre and the end of everything, it was easy indeed to consider
the steps of nature as unfolded in his favor; and if some unusual
phenomenon presented itself, it was considered to be without doubt a
warning from Heaven. If these illusions had had no other result than
the amelioration of the more timorous of the community one would
regret these ages of ignorance; but not only were these fancied
warnings of no use, seeing that once the danger passed, man returned
to his former state; but they also kept up among people imaginary
terrors, and revived the fatal resolutions caused by the fear of the
end of the world.
When one fancies the world is about to end,--and this has been
believed for more than a thousand years,--no solicitude is felt in the
work of improving this world; and, by the indifference or disdain into
which one falls, periods of famine and general misery are induced
which at certain times have overtaken our community. Why use the
wealth of a world which is going to perish? Why work, be instructed,
or rise in the progress of the sciences or arts? Much better to forget
the world, and absorb one's self in the barren contemplation of an
unknown life. It is thus that ages of ignorance weigh on man, and
thrust him further and further into darkness, while Science makes
known by its influence on the whole community, its great value, and
the magnitude of its aim.
The history of a comet would be an instructive episode of the great
history of the heavens. In it could be brought together the
description of the progressive movement of human thought, as well as
the astronomical theory of these extraordinary bodies. Let us take,
for example, one of the most memorable and best-known comets, and give
an outline of its successive passages near the Earth. Like the
planetary worlds, Comets belong to the solar system, and are subject
to the rule of the Star King. It is the universal law of gravitation
which guides their path; solar attraction governs them, as it governs
the movement of the planets and the small satellites. The chief point
of difference between them and the planets is, that their orbits are
very elongated; and, instead of being nearly circular, they take the
elliptical form. In consequence of the nature of these orbits, the
same comet may approach very near the Sun, and afterwards travel from
it to immense distances. Thus, the period of the Comet of 1680 has
been estimated at three thousand years. It approaches the Sun, so as
to be nearer to it than our Moon is to us, whilst it recedes to a
distance 853 times greater than the distance of the Earth from the
Sun. On the 17th of December, 1680, it was at its perihelion--that is,
at its greatest proximity to the Sun; it is now continuing its path
beyond the Neptunian orbit. Its velocity varies according to its
distance from the solar body. At its perihelion it travels thousands
of leagues per minute; at its aphelion it does not pass over more than
a few yards. Its proximity to the Sun in its passage near that body
caused Newton to think that it received a heat twenty-eight thousand
times greater than that we experience at the summer solstice; and
that this heat being two thousand times greater than that of red-hot
iron, an iron globe of the same dimensions would be fifty thousand
years entirely losing its heat. Newton added that in the end comets
will approach so near the Sun that they will not be able to escape the
preponderance of its attraction, and that they will fall one after the
other into this brilliant body, thus keeping up the heat which it
perpetually pours out into space. Such is the deplorable end assigned
to comets by the author of the "Principia," an end which makes De la
Brétonne say to Rétif: "An immense comet, already larger than Jupiter,
was again increased in its path by being blended with six other dying
comets. Thus displaced from its ordinary route by these slight shocks,
it did not pursue its true elliptical orbit; so that the unfortunate
thing was precipitated into the devouring centre of the Sun." "It is
said," added he, "that the poor comet, thus burned alive, sent forth
dreadful cries!"
[Illustration: A COMET]
It will be interesting, then, in a double point of view, to follow a
comet in its different passages in sight of the Earth. Let us take the
most important in astronomical history--the one whose orbit has been
calculated by Edmund Halley, and which was named after him. It was in
1682 that this comet appeared in its greatest brilliancy, accompanied
with a tail which did not measure less than thirty-two millions of
miles. By the observation of the path which it described in the
heavens, and the time it occupied in describing it, this astronomer
calculated its orbit, and recognized that the comet was the same as
that which was admired in 1531 and 1607, and which ought to have
reappeared in 1759. Never did scientific prediction excite a more
lively interest. The comet returned at the appointed time; and on the
12th of March, 1759, reached its perihelion. Since the year 12 before
the Christian era, it had presented itself twenty-four times to the
Earth. It was principally from the astronomical annals of China that
it was possible to follow it up to this period.
Its first memorable appearance in the history of France is that of
837, in the reign of Louis le Débonnaire. An anonymous writer of
chronicles of that time, named "The Astronomer," gave the following
details of this appearance, relative to the influence of the comet on
the imperial imagination:
"During the holy days of the solemnization of Easter, a phenomenon
ever fatal, and of gloomy foreboding, appeared in the heavens. As soon
as the Emperor, who paid attention to these phenomena, received the
first announcement of it, he gave himself no rest until he had called
a certain learned man and myself before him. As soon as I arrived, he
anxiously asked me what I thought of such a sign; I asked time of him,
in order to consider the aspects of the stars, and to discover the
truth by their means, promising to acquaint him on the morrow; but the
Emperor, persuaded that I wished to gain time, which was true, in
order not to be obliged to announce anything fatal to him, said to me:
'Go on the terrace of the palace and return at once to tell me what
you have seen, for I did not see this star last evening, and you did
not point it out to me; but I know that it is a comet; tell me what
you think it announces to me.' Then scarcely allowing me time to say
a word, he added: 'There is still another thing you keep back; it is
that a change of reign and the death of a prince are announced by this
sign.' And as I advanced the testimony of the prophet, who said: 'Fear
not the signs of the heavens as the nations fear them,' the prince
with his grand nature, and the wisdom which never forsook him, said,
'We must not only fear Him who has created both us and this star. But
as this phenomenon may refer to us, let us acknowledge it as a warning
from Heaven."
Louis le Débonnaire gave himself and his court to fasting and prayer,
and built churches and monasteries. He died three years later, in 840,
and historians have profited by this slight coincidence to prove that
the appearance of the comet was a harbinger of death. The historian,
Raoul Glader, added later: "These phenomena of the universe are never
presented to man without surely announcing some wonderful and terrible
event."
Halley's comet again appeared in April, 1066, at the moment when
William the Conqueror invaded England. It was pretended that it had
the greatest influence on the fate of the battle of Hastings, which
delivered over the country to the Normans.
A contemporary poet, alluding probably to the English diadem with
which William was crowned, had proclaimed in one place, "that the
comet had been more favorable to William than nature had been to
Caesar; the latter had no hair, but William had received some from the
comet." A monk of Malmesbury apostrophized the comet in these terms:
"Here thou art again, thou cause of the tears of many mothers! It is
long since I have seen thee, but I see thee now, more terrible than
ever; thou threatenest my country with complete ruin!"
In 1455, the same comet made a more memorable appearance still. The
Turks and Christians were at war, the West and the East seemed armed
from head to foot--on the point of annihilating each other. The
crusade undertaken by Pope Calixtus III. against the invading
Saracens, was waged with redoubled ardor on the sudden appearance of
the star with the flaming tail. Mahomet II. took Constantinople by
storm, and raised the siege of Belgrade. But the Pope having put aside
both the curse of the comet, and the abominable designs of the
Mussulmans, the Christians gained the battle, and vanquished their
enemies in a bloody fight. The _Angelus_ to the sound of bells dates
from these ordinances of Calixtus III. referring to the comet.
In his poem on astronomy, Daru, of the French Academy, describes this
episode in eloquent terms:
"Un autre Mahomet a-t-il d'un bras puissant
Aux murs de Constantine arboré le croissant:
Le Danube étonné se trouble au bruit des armes,
La Grèce est dans les fers, l'Europe est en alarmes;
Et pour comble d'horreur, l'astre au visage ardent
De ses ailes de feu va couvrir l'Occident.
Au pied de ses autels, qu'il ne saurait défendre,
Calixte, l'oeil en pleurs, le front convert de cendre,
Conjure la comète, objet de tant d'effroi:
Regarde vers les cieux, pontife, et lève-toi!
L'astre poursuit sa course, et le fer d'Huniade
Arrête le vainqueur, qui tombe sous Belgrade.
Dans les cieux cependant le globe suspendu,
Par la loi générale à jamais retenu,
Ignore les terreurs, l'existence de Rome,
Et la Terre peut-être, et jusqu'au nom de l'homme,
De l'homme, être crédule, atome ambitieux,
Qui tremble sous un prêtre et qui lit dans les cieux."
This ancient comet witnessed many revolutions in human history, at
each of its appearances, even in its later ones, in 1682, 1759, 1835;
it was also presented to the Earth under the most diverse aspects,
passing through a great variety of forms, from the appearance of a
curved sabre, as in 1456, to that of a misty head, as in its last
visit. Moreover, this is not an exception to the general rule, for
these mysterious stars have had the gift of exercising a power on the
imagination which plunged it in ecstasy or trouble. Swords of fire,
bloody crosses, flaming daggers, spears, dragons, fish, and other
appearances of the same kind, were given to them in the middle ages
and the Renaissance.
Comets like those of 1577 appear, moreover, to justify by their
strange form the titles with which they are generally greeted. The
most serious writers were not free from this terror. Thus, in a
chapter on celestial monsters, the celebrated surgeon, Ambroise Paré,
described the comet of 1528 under the most vivid and frightful colors:
"This comet was so horrible and dreadful that it engendered such great
terror to the people, that they died, some with fear, others with
illness. It appeared to be of immense length, and of blood color; at
its head was seen the figure of a curved arm, holding a large sword in
the hand as if it wished to strike. At the point of the sword there
were three stars, and on either side was seen a great number of
hatchets, knives, and swords covered with blood, amongst which were
numerous hideous human faces, with bristling beards and hair."
The imagination has good eyes when it exerts itself. The great and
strange variety of cometary aspects is described with exactitude by
Father Souciet in his Latin poem on comets. "Most of them," says he,
"shine with fires interlaced like thick hair, and from this they have
taken the name of comets. One draws after it the twisted folds of a
long tail; another appears to have a white and bushy beard; this one
throws a glimmer similar to that of a lamp burning during the night;
that one, O Titan! represents thy resplendent face; and this other, O
Phoebe! the form of thy nascent horns. There are some which bristle
with twisted serpents. Shall I speak of those armies which have
sometimes appeared in the air? of those clouds which follow as it were
along a circle, or which resemble the head of Medusa? Have there not
often been seen figures of men or savage animals?
"Often, in the gloom of night, lighted up by these sad fires, the
horrible sound of arms is heard, the clashing of swords which meet in
the clouds, the ether furiously resounding with fearful din which
crush the people with terror. All comets have a melancholy light, but
they have not all the same color. Some have a leaden color; others
that of flame or brass. The fires of some have the redness of blood;
others resemble the brightness of silver. Some again are azure; others
have the dark and pale color of iron. These differences come from the
diversity of the vapors which surround them, or from the different
manner in which they receive the Sun's rays. Do you not see in our
fires, that various kinds of wood produce different colors? Pines and
firs give a flame mixed with thick smoke, and throw out little light.
That which rises from sulphur and thick bitumen is bluish. Lighted
straw gives out sparks of a reddish color. The large olive, laurel,
ash of Parnassus, etc., trees which always retain their sap, throw a
whitish light similar to that of a lamp. Thus, comets whose fires are
formed of different materials, each take and preserve a color which is
peculiar to them."
Instead of being a cause of fear and terror, the variety and
variability of the aspect of comets ought rather to indicate to us the
harmlessness of their nature.
[Illustration]
THE TOTAL SOLAR ECLIPSE OF 1883
_AN ASTRONOMERS VOYAGE TO FAIRY-LAND._
(FROM THE ATLANTIC MONTHLY, MAY, 1890.)
BY PROF. E.S. HOLDEN.
[Illustration]
In 1883 calculations showed that a solar eclipse of unusually long
duration (5 minutes, 20 seconds) would occur in the South Pacific
Ocean. The track of the eclipse lay south of the equator, but north of
Tahiti. There were in fact only two dots of coral islands on the
charts in the line of totality, Caroline Island, and one hundred and
fifty miles west Flint Island (longitude 150 west, latitude 10 south).
Almost nothing was known of either of these minute points. The station
of the party under my charge (sent out by the United States government
under the direction of the National Academy of Sciences) was to be
Caroline Islands.
Every inch of that island (seven miles long, a mile or so broad) is
familiar now; but it is almost ludicrous to recollect with what
anxiety we pored over the hydrographic charts and sailing instructions
of the various nations, to find some information, however scanty,
about the spot which was to be our home for nearly a month. All that
was known was that this island had formerly been occupied as a guano
station. There was a landing _then_.
After the _personnel_ of the party had been decided on, there were the
preparations for its subsistence to be looked out for. How to feed
seventeen men for twenty-one days? Fortunately the provisions that we
took, and the fresh fish caught for us by the natives, just sufficed
to carry us through with comfort and with health.
In March of 1883 we sailed from New York, and about the same time a
French expedition left Europe bound for the same spot. From New York
to Panama, from Panama to Lima, were our first steps. Here we joined
the United States steamship Hartford, Admiral Farragut's flagship, and
the next day set sail for our destined port,--if a coral reef
surrounded by a raging surf can be called a port. About the same time
a party of French observers under Monsieur Janssen, of the Paris
Academy of Sciences, left Panama in the _Eclaireur_.
[Illustration: BIRD'S EYE VIEW OF THE CAROLINE ISLANDS.]