necessary trouble, can easily make a little model of Saturn and his ring
system, which will very prettily illustrate the effect of the rings both
in reflecting light to the planet's darkened hemisphere and in cutting
off light from the planet's illuminated hemisphere. Take a ball, say an
ordinary hand-ball, and pierce it through the centre with a fine
knitting-needle. Cut out a flat ring of card, proportioned to the ball
as the ring system of Saturn to his ball. (If the ball is two inches in
diameter, strike out on a sheet of cardboard two concentric circles, one
of them with a radius of a little more than an inch and a half, the
other with a radius of about two inches and three-eights, and cut out
the ring between these two circles.) Thrust the knitting-needle through
this ring in such a way that the ball shall lie in the middle of the
ring, as the globe of Saturn hangs (without knitting-needle connections)
in the middle of his ring system. Thrust another knitting-needle
centrally through the ball square to the plane of the ring, and use this
second needle, which we may call the polar one, as a handle. Now take
the ball and ring into sunlight, or the light of a lamp or candle,
holding them so that the shadow of the ring is as thin as possible. This
represents the position of the shadow at the time of Saturnian spring or
autumn. Cause the shadow slowly to shift until it surrounds the part of
the ball through which the polar needle passes on one side. This will
represent the position of the shadow at the time of midwinter for the
hemisphere corresponding to that side of the ball. Notice that while the
shadow is traversing this half of the ball, the side of the ring which
lies towards that half is in shadow, so that a fly or other small insect
on that half of the ball would see the darkened side of the ring. A
Saturnian correspondingly placed would get no reflected sunlight from
the ring system. Move the ball and ring so that the shadow slowly
returns to its first position. You will then have illustrated the
changes taking place during one half of a Saturnian year. Continue the
motion so that the shadow passes to the other half of the ball, and
finally surrounds the other point through which the polar needle passes.
The polar point which the shadow before surrounded will now be seen to
be in the light, and this half of the ball will illustrate the
hemisphere of Saturn where it is midsummer. It will also be seen that
the side of the ring towards this half of the ball is now in the light,
so that a small insect on this half of the ball would see the bright
side of the ring. A Saturnian correspondingly placed would get reflected
sunlight from the ring system _both by day and by night_. Moving the
ball and ring so that the shadow returns to its first position, an
entire Saturnian year will have been illustrated. These changes can be
still better shown with a Saturnian orrery (see plate viii. of my
Saturn), which can be very easily constructed.
[31] Not 'of course' because Tycho used it, for, like other able
students of science, he made mistakes from time to time. Thus he argued
that the earth cannot rotate on her axis, because if she did bodies
raised above her surface would be left behind--an argument which even
the mechanical knowledge of his own time should have sufficed to
invalidate, though it is still used from time to time by paradoxers of
our own day.
[32] Chinese chronicles contain other references to new stars. The
annals of Ma-touan-lin, which contain the official records of remarkable
appearances in the heavens, include some phenomena which manifestly
belong to this class. Thus they record that in the year 173 a star
appeared between the stars which mark the hind feet of the Centaur. This
star remained visible from December in that year until July in the next
(about the same time as Tycho Brahe's and Kepler's new stars, presently
to be described). Another star, assigned by these annals to the year
1011, seems to be the same as a star referred to by Hepidannus as
appearing A.D. 1012. It was of extraordinary brilliancy, and remained
visible in the southern part of the heavens during three months. The
annals of Ma-touan-lin assign to it a position low down in Sagittarius.
[33] Still a circumstance must be mentioned which tends to show that the
star may have been visible a few hours earlier than Dr. Schmidt
supposed. Mr. M. Walter, surgeon of the 4th regiment, then stationed in
North India, wrote (oddly enough, on May 12, 1867, the first anniversary
of Mr. Birmingham's discovery) as follows to Mr. Stone:--'I am certain
that this same conflagration was distinctly perceptible here at least
six hours earlier. My knowledge of the fact came about in this wise. The
night of the 12th of May last year was exceedingly sultry, and about
eight o'clock on that evening I got up from the tea-table and rushed
into my garden to seek a cooler atmosphere. As my door opens towards the
east, the first object that met my view was the Northern Crown. My
attention was at once arrested by the sight of a strange star outside
the crown' (that is, outside the circlet of stars forming the diadem,
not outside the constellation itself). The new star 'was then certainly
quite as bright--I rather thought more so--as its neighbour Alphecca,'
the chief gem of the crown. 'I was so much struck with its appearance,
that I exclaimed to those indoors, "Why, here is a new comet!'" He made
a diagram of the constellation, showing the place of the new star
correctly. Unfortunately, Mr. Walter does not state why he is so
confident, a year after the event, that it was on the 12th of May, and
not on the 13th, that he noticed the new star. If he fixed the date only
by the star's appearance as a second-magnitude star, his letter proves
nothing; for we know that on the 13th it was still shining as brightly
as Alphecca, though on the 14th it was perceptibly fainter.
[34] The velocity of three or four miles per second inferred by the
elder Struve must now be regarded (as I long since pointed out would
prove to be the case) as very far short of the real velocity of our
system's motion through stellar space.
[35] M. Cornu's observations are full of interest, and he deserves
considerable credit for his energy in availing himself of the few
favourable opportunities he had for making them. But he goes beyond his
province in adding to his account of them some remarks, intended
apparently as a reflection on Mr. Huggins's speculations respecting the
star in the Northern Crown. '_I_,' says M. Cornu, 'will not try to form
any hypothesis about the cause of the outburst. To do so would be
unscientific, and such speculations, though interesting, cumber science
wofully.' This is sheer nonsense, and comes very ill from an observer
whose successes in science have been due entirely to the employment of
methods of observation which would have had no existence had others been
as unready to think out the meaning of observed facts as he appears to
be himself.
[36] The same peculiarity has been noticed since the discovery of the
dark ring, the space within that ring being observed by Coolidge and G.
Bond at Harvard in 1856 to be apparently darker than the surrounding
sky.
[37] I cannot understand why Mr. Webb, in his interesting little work,
_Celestial Objects for Common Telescopes_, says that the satellite
theory of the rings certainly seems insufficient to account for the
phenomena of the dark ring. It seems, on the contrary, manifest that the
dark ring can scarcely be explained in any other way. The observations
recently made are altogether inexplicable on any other theory.
[38] A gentleman, whose acquaintance I made in returning from America
last spring, assured me that he had found demonstrative evidence showing
that a total eclipse of the moon then occurred; for he could prove that
Abraham's vision occurred at the time of full moon, so that it could not
otherwise have been dark when the sun went down (v. 17). But the horror
of great darkness occurred when the sun was going down, and total
eclipses of the moon do not behave that way--at least, in our time.
[39] It is not easy to understand what else it could have been. The
notion that a conjunction of three planets, which took place shortly
before the time of Christ's birth, gave rise to the tradition of the
star in the east, though propounded by a former president of the
Astronomical Society, could hardly be entertained by an astronomer,
unless he entirely rejected Matthew's account, which the author of this
theory, being a clergyman, can scarcely have done.
[40] As, for instance, when he makes Homer say of the moon that
Around her throne the vivid planets roll,
And stars unnumbered gild the glowing pole.
It is difficult, indeed, to understand how so thorough an astronomer as
the late Admiral Smyth could have called the passage in which these
lines occur one of the finest bursts of poetry in our language, except
on the principle cleverly cited by Waller when Charles II. upbraided him
for the warmth of his panegyric on Cromwell, that 'poets succeed better
with fiction than with truth.' Macaulay, though not an astronomer,
speaks more justly of the passage in saying that this single passage
contains more inaccuracies than can be found in all Wordsworth's
'Excursion.'
[41] It may be necessary to throw in here a few words of explanation,
lest the non-astronomical reader should run away with the idea that the
so-called exact science is a very inexact science indeed, so far as
comets are concerned. The comet of 1680 was one of those which travel on
a very eccentric orbit. Coming, indeed, from out depths many times more
remote than the path even of the remotest planet, Neptune, this comet
approached nearer to the sun than any which astronomers have ever seen,
except only the comet of 1843. When at its nearest its nucleus was only
a sixth part of the sun's diameter from his surface. Thus the part of
the comet's orbit along which astronomers traced its motion was only a
small part at one end of an enormously long oval, and very slight errors
of observation were sufficient to produce very large errors in the
determination of the nature of the comet's orbit. Encke admitted that
the period might, so far as the comparatively imperfect observations
made in 1680 were concerned, be any whatever, from 805 years to many
millions of years, or even to infinity--that is, the comet might have a
path not re-entering into itself, but carrying the comet for ever away
from the sun after its one visit to our system.
[42] For a portion of the passages which I have quoted in this essay I
am indebted to Guillemin's 'Treatise on Comets,' a useful contribution
to the literature of the subject, though somewhat inadequate so far as
exposition is concerned.
[43] Something very similar happened only a few years ago, so that we
cannot afford to laugh too freely at the terrors of France in 1773. It
was reported during the winter of 1871-1872, that Plantamour, the Swiss
astronomer, had predicted the earth's destruction by a comet on August
12, 1872. Yet there was no other foundation for this rumour than the
fact that Plantamour, in a lecture upon comets and meteors, had stated
that the meteors seen on August 10, 11, and 12 are bodies following in
the track of a comet whose orbit passes very near to the earth's. It was
very certainly known to astronomers that there could be no present
danger of a collision with this comet, for the comet has a period of at
least 150 years, and had last passed close to the earth's orbit (not to
the earth herself, be it understood) in 1862. But it was useless to
point this out. Many people insisted on believing that on August 12,
1872, the earth would come into collision, possibly disastrous, with a
mighty comet, which Plantamour was said to have detected and to have
shown by a profound calculation to be rushing directly upon our
unfortunate earth.
[44] A rather amusing mistake was made by the stenographers of a New
York paper in reporting the above sentence, which I happened to quote in
a lecture upon Comets and Meteors. Instead of Paradise they wrote Paris.
Those acquainted with Pitman's system of short-hand, the one most
commonly employed by reporters, will easily understand how the mistake
was made, the marks made to represent the consonants p, r, d, and s
differing little from those made to represent the consonants p, r, and s
(the 'd' or 't' sound is represented, or may be represented, by simply
shortening the length of the sign for the preceding consonant). The
mistake led naturally to my remarking in my next lecture that I had not
before known how thoroughly synonymous the words are in America, though
I had heard it said that 'Good Americans, when they die, go to Paris.'
[45] On the occasion of my first visit to America, in 1873, I for the
first time succeeded in obtaining a copy of this curious pamphlet. It
had been mentioned to me (by Emerson, I think) as an amusing piece of
trickery played off by a scientific man on his brethren; and Dr. Wendell
Holmes, who was present, remarked that he had a copy in his possession.
This he was good enough to lend me. Soon after, a valued friend in New
York presented me with a copy.
[46] This Locke must not be confounded with Richard Lock, the
circle-squarer and general paradoxist, who flourished a century earlier.
[47] The nurses' tale is, that the man was sent to the moon by Moses for
gathering sticks on the Sabbath, and they refer to the cheerful story in
Numbers xv. 32-36. According to German nurses the day was not the
Sabbath, but Sunday. Their tale runs as follows: 'Ages ago there went
one Sunday an old man into the woods to hew sticks. He cut a faggot and
slung it on a stout staff, cast it over his shoulder, and began to
trudge home with his burthen. On his way he met a handsome man in Sunday
suit, walking towards the church. The man stopped, and asked the
faggot-bearer; "Do you know that this is Sunday on earth, when all must
rest from their labours?" "Sunday on earth or Monday in heaven, it's all
one to me?" laughed the wood-cutter. "Then bear your bundle for ever!"
answered the stranger. "And as you value not Sunday on earth, yours
shall be a perpetual Moon-day in heaven; you shall stand for eternity in
the moon, a warning to all Sabbath-breakers." Thereupon the stranger
vanished; and the man was caught up with his staff and faggot into the
moon, where he stands yet.' According to some narrators the stranger was
Christ; but whether from German laxity in such matters or for some other
reason, no text is quoted in evidence, as by the more orthodox British
nurses. Luke vi. 1-5 might serve.
[48] Milton's opinion may be quoted against me here; and as received
ideas respecting angels, good and bad, the fall of man, and many other
such matters, are due quite as much to Milton as to any other authority,
his opinion must not be lightly disregarded. But though, when Milton's
Satan 'meets a vast vacuity' where his wings are of no further service
to him,
'All unawares
Flutt'ring his pennons vain, plumb down he drops
Ten thousand fathoms deep, and to this hour
Down had been falling, had not by ill chance
The strong rebuff of some tumultuous cloud,
Instinct with fire and nitre, hurried him
As many miles aloft,'
yet this was written nearly a quarter of a century before Newton had
established the law of gravity. Moreover, there is no evidence to show
in what direction Satan fell; 'above is below and below above,' says
Richter, 'to one stripped of gravitating body;' and whether Satan was
under the influence of gravity or not, he would be practically exempt
from its action when in the midst of that 'dark, illimitable ocean' of
space,
'Without bound,
Without dimensions, where length, breadth, and height,
And time and place are lost.'
His lighting 'on Niphates' top,' and overleaping the gate of Paradise,
may be used as arguments either way. On the whole, I must (according to
my present lights) claim for Satan a freedom from all scientific
restraints. This freedom is exemplified by his showing all the kingdoms
of the world from an exceeding high mountain, thus affording the first
practical demonstration of the flat-earth theory, the maintenance of
which led to poor Mr. Hampden's incarceration.
[49] The _Sun_ itself claimed to have established the veracity of the
account in a manner strongly recalling a well-known argument used by
orthodox believers in the Bible account of the cosmogony. Either, say
these, Moses discovered how the world was made, or the facts were
revealed to him by some one who had made the discovery: but Moses could
not have made the discovery, knowing nothing of the higher departments
of science; therefore, the account came from the only Being who could
rationally be supposed to know anything about the beginning of the
world. 'Either,' said the _New York Sun_, speaking of a mathematical
problem discussed in the article, 'that problem was predicated by us or
some other person, who has thereby made the greatest of all modern
discoveries in mathematical astronomy. We did not make it, for we know
nothing of mathematics whatever; therefore, it was made by the only
person to whom it can rationally be ascribed, namely Herschel the
astronomer, its only avowed and undeniable author.' In reality,
notwithstanding this convincing argument, the problem was stolen by
Locke from a paper by Olbers, shortly before published, and gave the
method followed by Beer and Maedler throughout their selenographical
researches in 1833-37.
[50] I had at the same time the good fortune to satisfy in equal degree,
though quite unexpectedly, an English student of the sun, who at that
time bore me no great good-will. Something in the article chanced to
suggest that it came from another, presumably a rival, hand; while an
essay which appeared about the same time (the spring of 1872) was
commonly but erroneously attributed to me. Accordingly, a leading
article in _Nature_ was devoted to the annihilation of the writer
supposed to be myself, and to the lavish and quite undeserved laudation
of the article I had written, which was selected as typifying all the
good qualities which an article of the kind should possess. Those
acquainted with the facts were not a little amused by the mistake.
[51] The Astronomer-Royal once told me that he had found that few
persons have a clear conception of the fact that the stars rise and set.
Still fewer know how the stars move, which stars rise and set, which are
always above the horizon, which move on large circles, which on small
ones; though a few hours' observation on half-a-dozen nights in the year
(such observations being continuous, but made only at hourly intervals)
would show dearly how the stars move. It is odd to find even some who
write about astronomy making mistakes on matters so elementary. For
instance, in a primer of astronomy recently published, it is stated that
the stars which pass overhead in London rise and set on a slant--the
real fact being that _those_ stars never rise or set at all, never
coming within some two dozen moon-breadths of the horizon.
[52] In passing let me note that, of course, I am not discussing the
arguments of paradoxists with the remotest idea of disproving them. They
are not, in reality, worth the trouble. But they show where the general
reader of astronomical text-books, and other such works, is likely to go
astray, and thus conveniently indicate matters whose explanation may be
useful or interesting.
[53] Sterne anticipated this paradoxist in (jestingly) attributing
glassiness to an inferior planet. He made the inhabitants, however, not
the air, glassy. 'The intense heat of the country,' he says, speaking of
the planet Mercury, 'must, I think, long ago have vitrified the bodies
of the inhabitants to suit them for the climate; so that all the
tenements of their souls may be nothing else, for aught the soundest
philosophy can show to the contrary, but one fine transparent body of
clear glass; so that till the inhabitant grows old and tolerably
wrinkled, whereby the rays of light become monstrously refracted, or
return reflected from the surface, etc., his soul might as well play the
fool out o' doors as in her own house.'
[54] It will be seen from Table X. of my treatise on Saturn that the
ring disappeared on December 12, remaining invisible (because turning
its dark side earthwards) till the spring of 1613. But on December 4,
the ring must have been quite invisible in a telescope so feeble as
Galileo's. The ring then would have been little more than a fine line of
light as seen with one of our powerful modern telescopes.
[55] _North British Review_ for August 1860.
[56] He had, indeed, at an earlier stage, shown a marvellous ignorance
of astronomy by the remark, which doubtless appeared to him a safe one,
that when he saw a planet on the sun in September he supposed it was
Mercury; a September transit of Mercury being as impossible as an
eclipse of the sun during the moon's third quarter.
[57] It is, by the way, somewhat amusing to find Baron Humboldt
referring a question of this sort to the great mathematician Gauss, and
describing the problem as though it involved the most profound
calculations. Ten minutes should suffice to deal with any problem of the
kind.
Transcriber's Note
The following typographical errors were corrected.
Page Error Correction
4 Julias Julius
35 genuis genius
36 artficers artificers
37 signfies signifies
footnote 14 preplexing perplexing
45 Chaldean Chaldaean
46 Chaldeans Chaldaeans
225 peruquier perruquier
237 peruque perruque
281 Northfolk Norfolk
350 ascant askant