Myths and Marvels of Astronomy
It is perhaps unnecessary to add that observations were made as
requested. Many photographs of the sun also were taken during the hours
when Vulcan, if he exists at all, might be expected to cross the sun's
face. But the 'planet of romance,' as Abbe Moigno has called Vulcan,
failed to appear, and the opinion I had expressed last October
('English Mechanic and World of Science,' for October 27, 1876, p. 160),
that Vulcan might perhaps better be called the 'planet of fiction' was
_pro tanto_ confirmed. Nevertheless, I would not be understood to mean
by the word 'fiction' aught savouring of fraud so far as Lescarbault is
concerned--I prefer the North Briton's view of Lescarbault's spot, that
so to speak, it was
... the blot upon his brain,
That _would_ show itself without.
I have left small space to treat of other fancied discoveries among the
orbs of heaven. Yet there are some which are not only interesting but
instructive, as showing how even the most careful observers may be led
astray. In this respect the mistakes into which observers of great and
well deserved eminence have fallen are specially worthy of attention.
With the description of three such mistakes, made by no less an
astronomer than Sir W. Herschel, I shall bring this paper to a close.
When Sir W. Herschel examined the planet Uranus with his most powerful
telescope he saw the planet to all appearance girt about by two rings at
right angles to one another. The illusion was so complete that Herschel
for several years remained in the belief that the rings were real. They
were, however, mere optical illusions, due to the imperfect defining
qualities of the telescope with which he observed the planet. Later he
wrote that 'the observations which tend to ascertain' (indicate?) 'the
existence of rings not being satisfactorily supported, it will be proper
that surmises of them should either be given up, as ill-founded, or at
least reserved till superior instruments can be provided.'
Sir W. Herschel was more completely misled by the false Uranian
satellites. He had seen, as he supposed, no less than six of these
bodies. As only two of these had been seen again, while two more were
discovered by Lassell, the inference was that Uranus has eight
satellites in all. These for a long time flourished in our text-books of
astronomy; and many writers, confident in the care and skill of Sir W.
Herschel, were unable for a long time to believe that he had been
deceived. Thus Admiral Smyth, in his 'Celestial Cycle,' wrote of those
who doubted the extra satellites:--'They must have but a meagre notion
of Sir W. Herschel's powerful means, his skill in their application, and
his method of deliberate procedure. So far from doubting there being six
satellites' (this was before Lassell had discovered the other two) 'it
is highly probable that there are still more.' Whewell, also, in his
'Bridgewater Treatise,' says, 'that though it no longer appears probable
that Uranus has a ring like Saturn, he has at least five satellites
which are visible to us, and we believe that the astronomer will hardly
deny that he' (Uranus, not the astronomer), 'may possibly have thousands
of smaller ones circulating about him.' But in this case Sir W.
Herschel, anxiously though he endeavoured to guard against the
possibility of error, was certainly mistaken. Uranus may, for anything
that is known to the contrary, have many small satellites circulating
about him, but he certainly has not four satellites (besides those
known) which could have been seen by Sir W. Herschel with the telescope
he employed. For the neighbourhood of the planet has been carefully
examined with telescopes of much greater power by observers who with
those telescopes have seen objects far fainter than the satellites
supposed to have been seen by the elder Herschel.
The third of the Herschelian myths was the lunar volcano in eruption,
which he supposed he had seen in progress in that part of the moon which
was not at the time illuminated by the sun's rays. He saw a bright
star-like point of light, which corresponded in position with the crater
of the lunar mountain Aristarchus. He inferred that a volcano was in
active eruption because the brightness of the point of light varied from
time to time, and also because he did not remember to have seen it
before under the same conditions. There is no doubt something very
remarkable in the way in which this part of the moon's surface shines
when not illumined by the sun. If it were always bright we should
conclude at once that the earth-light shining upon it rendered it
visible. For it must be remembered that the part of the moon which looks
dark (or seems wanting to the full disc) is illuminated by our earth,
shining in the sky of the moon as a disc thirteen times as large as that
of the moon we see, and with the same proportion of its disc sunlit as
is dark in the moon's disc. Thus when the moon is nearly new our earth
is shining in the lunar skies as a nearly full moon thirteen times as
large as ours. The light of this noble moon must illumine the moon's
surface much more brightly than a terrestrial landscape is illumined by
the full moon, and if any parts of her surface are very white they will
shine out from the surface around, just as the snow-covered peak of a
mountain shines out upon a moonlit night from among the darker hills and
dales and rocks and forests of the landscape. But Herschel considered
that the occasional brightness of the crater Aristarchus could not be
thus explained. The spot had been seen before the time of Herschel's
observations by Cassini and others. It has been seen since by Captain
Kater, Francis Baily, and many others. Dr. Maskelyne tells us that in
March 1794 it was seen by the naked eye by two persons.
Baily thus describes the appearance presented by this lunar crater on
December 22, 1835: 'Directed telescope to the moon, and pointing it to
the dark part in the vicinity of Aristarchus, soon saw the outline of
that mountain very distinctly, formed like an irregular nebula. Nearly
in the centre was a light resembling that of a star of the ninth or
tenth magnitude. It appeared by glimpses, but at times was brilliant,
and visible for several seconds together.'
There can be little doubt, however, that the apparent brightness of this
lunar crater, or rather of its summit, is due to some peculiar quality
in the surface, which may perhaps be covered by some crystalline or
vitreous matter poured out in the far distant time when the crater was
an active one. Prof. Shaler, who examined the crater when it was
illuminated only by earthshine, with the fine 15-inch telescope of the
Harvard Observatory (Cambridge U.S.), says that he has been able to
recognise nearly all the craters over 15 miles in diameter in the dark
part. 'There are several degrees of brightness,' he says, 'observable in
the different objects which shine out by the earth-light. This fact
probably explains the greater part of the perplexing statements
concerning the illumination of certain craters. It certainly accounts
for the volcanic activity which has so often been supposed to be
manifested by Aristarchus. Under the illumination by the earth-light
this is by far the brightest object on the dark part of the moon's face,
and is visible much longer and with poorer glasses than any other object
there.'
Here my record of astronomical myths must be brought to a close. It will
be noticed that in every instance either the illusion has affected the
actual observations of eminent and skilful astronomers, or has caused
such astronomers to put faith for a while in illusory observations. Had
I cared to include the mistakes which have been made by or have misled
observers of less experience, I could have filled many sheets for each
page of the present article. But it has seemed to me more instructive
to show how error may affect the observations even of the most careful
and deservedly eminent astronomers, how even the most cautious may be
for a time misled by the mistakes of inferior observers, especially when
the fact supposed to have been observed accords with preconceived
opinions.
XII.
_THE ORIGIN OF THE CONSTELLATION-FIGURES._
Although the strange figures which astronomers still allow to straggle
over their star maps no longer have any real scientific interest, they
still possess a certain charm, not only for the student of astronomy,
but for many who care little or nothing about astronomy as a science.
When I was giving a course of twelve lectures in Boston, America, a
person of considerable culture said to me, 'I wish you would lecture
about the constellations; I care little about the sun and moon and the
planets, and not much more about comets; but I have always felt great
interest in the Bears and Lions, the Chained and Chaired Ladies, King
Cepheus and the Rescuer Perseus, Orion, Ophiuchus, Hercules, and the
rest of the mythical and fanciful beings with which the old astronomers
peopled the heavens. I say with Carlyle, "Why does not some one teach me
the constellations, and make me at home in the starry heavens, which are
always overhead, and which I don't half know to this day."' We may
notice, too, that the poets by almost unanimous consent have recognised
the poetical aspect of the constellations, while they have found little
to say about subjects which belong especially to astronomy as a science.
Milton has indeed made an Archangel reason (not unskilfully for Milton's
day) about the Ptolemaic and Copernican systems, while Tennyson makes
frequent reference to astronomical theories. 'There sinks the nebulous
star we call the Sun, if that hypothesis of theirs be sound,' said Ida;
but she said no more, save 'let us down and rest,' as though the subject
were wearisome to her. Again, in the Palace of Art the soul of the poet
having built herself that 'great house so royal, rich, and wide,'
thither--
... when all the deep unsounded skies
Shuddered with silent stars, she clomb,
And as with optic glasses her keen eyes
Pierced through the mystic dome,
Regions of lucid matter taking forms,
Brushes of fire, hazy gleams,
Clusters and beds of worlds and beelike swarms
Of suns, and starry streams:
She saw the snowy poles of moonless Mars,
That marvellous round of milky light
Below Orion, and those double stars
Whereof the one more bright
Is circled by the other.
But the poet's soul so wearied of these astronomical researches that the
beautiful lines I have quoted disappeared (more's the pity) from the
second and all later editions. Such exceptions, indeed, prove the rule.
Poets have been chary in referring to astronomical researches and
results, full though these have been of unspeakable poetry; while from
the days of Homer to those of Tennyson, the constellations which
'garland the heavens' have always been favourite subjects of poetic
imagery.
It is not my present purpose, however, to discuss the poetic aspect of
the constellations. I propose to inquire how these singular figures
first found their way to the heavens, and, so far as facts are available
for the purpose, to determine the history and antiquity of some of the
more celebrated constellations.
Long before astronomy had any existence as a science men watched the
stars with wonder and reverence. Those orbs, seemingly countless--which
bespangle the dark robe of night--have a charm and beauty of their own
apart from the significance with which the science of astronomy has
invested them. The least fanciful mind is led to recognise on the
celestial concave the emblems of terrestrial objects, pictured with more
or less distinctness among the mysterious star-groupings. We can imagine
that long before the importance of the study of the stars was