of substances which are formed from the same chemical elements as
those you find on the earth. Not improbably I may have had some iron
in my constitution, and also sodium and carbon, to mention only a
few of the most familiar elements. I only weighed an ounce or two,
perhaps more, perhaps less—but you could probably have held me in
your closed hand, or put me into your waistcoat pocket. You would
have described me as a sort of small stone, yet I think you would
have added that I was very unlike the ordinary stones with which you
were familiar. I have led a life of the most extraordinary activity;
I have never known what it was to stay still; I have been ever on
the move. Through the solitudes of space I have dashed along with a
speed which you can hardly conceive. Compare my ordinary motion with
your most rapid railway trains; my journey will be done ere the best
locomotive ever built could have drawn the train out of the station.
Pit me against your rifle bullets, against the shots from your
one-hundred-ton guns; before the missile from the mightiest piece
of ordnance ever fired shall have gone ten yards I have gone 1,000
yards. I do not assert that my speed has been invariable—sometimes it
has been faster, sometimes it has been slower; but I have generally
done my million miles a day at the very least. Such has been my
career, not for hours or days, but for years and for centuries,
probably for untold ages. And the grand catastrophe in which I
vanished has been befitting to a life of such transcendent excitement
and activity; I have perished instantly, and in a streak of splendor.
In the course of my immemorial wanderings I have occasionally passed
near some of the great bodies in the heavens; I have also not
improbably in former years hurried by that globe on which you live.
On those occasions you never saw me, you never could have seen me,
not even if you had used the mightiest telescope that has ever been
directed to the heavens. But too close an approach to your globe was
at last the occasion of my fall. You must remember that you live on
the earth buried beneath a great ocean of air. Viewed from outside
space, your earth is seen to be a great ball, everywhere swathed
with this thick coating of air. Beyond the appreciable limits of the
air stretches the open space, and there it is that my prodigious
journeys have been performed. Out there we have a freedom to move of
which you who live in a dense atmosphere have no conception. Whenever
you attempt to produce rapid motion on the earth, the resistance of
your air largely detracts from the velocity that would be otherwise
attainable. Your quick trains are impeded by air, your artillery
ranges are shortened by it. Movements like mine would be impossible
in air like yours.
“And this air it is which has ultimately compassed my destruction.
So long as I merely passed near your earth, but kept clear of that
deadly net which you have spread, in the shape of your atmosphere,
to entrap the shooting stars, all went well with me. I felt the
ponderous mass of the earth, and I swerved a little in compliance
with its attraction; but my supreme velocity preserved me, and I
hurried past unscathed. I had many narrow escapes from capture
during the lapse of those countless ages in which I have been
wandering through space. But at last I approached once too often to
the earth. On this fatal occasion my course led me to graze your
globe so closely that I could not get by without traversing the
higher parts of the atmosphere. Accordingly, a frightful catastrophe
immediately occurred. Not to you; it did you no harm; indeed, quite
the contrary. My dissolution gave you a pleasing and instructive
exhibition. It was then, for the first time, that you were permitted
to see me, and you called me a shooting star or a meteor.
“When from the freedom of open space I darted into the atmosphere,
I rubbed past every particle of air which I touched in my impetuous
flight, and in doing so I experienced the usual consequence of
friction—I was warmed by the operation.
“You can readily comprehend the immense quantity of heat that will
have been produced ere friction could deprive me of a speed of twenty
miles a second. That heat not merely warmed me, but I rapidly became
red-hot, white-hot, then I melted, even though composed of materials
of a most refractory kind. Still friction had much more to do, and
it actually drove me off into vapor, and I vanished. You, standing
on your earth many miles below, never saw me—never could have seen
me—until this supreme moment, when, glowing with an instantaneous
fervor, I for a brief second became visible.
“Nature knows no annihilation, and though I had been driven off
into vapor and the trial by fire had scattered and dispersed me,
yet in the lofty heights of the atmosphere those vapors cooled and
condensed. They did not, they never could again reunite and reproduce
my pristine structure. Here and there in wide diffusion I repassed
from the vaporous to the solid form, and in this state I wore the
appearance of a streak of minute granules distributed all along the
highway I had followed. These granules gradually subsided through
the air to the earth. On Alpine snows, far removed from the haunts of
men and from contamination of chimneys, minute particles have been
gathered, many of which have unquestionably been derived from the
scattered remains of shooting stars. Into the sea similar particles
are forever falling, and they have been subsequently dredged up from
profound depths, having subsided through an ocean of water after
sinking through an ocean of air.”
Those splendid shooting stars which are often called fire-balls move
in every direction. They come from the east, and from the west,
from the north, and from the south. There is no hour of the night
at which they have not occasionally been seen. Even in daylight it
has happened not once or twice, but on several occasions, that a
brilliant meteor has forced itself upon our astonished notice. They
generally first make their appearance at a height which is between
fifty and one hundred miles above the ground. They hurry down their
inclined path, but generally become extinguished while still at least
twenty miles aloft. In their more ambitious flights meteors have been
known to span a kingdom. Nor are even greater strides unrecorded.
The length of a continent may be compared with the track of that
terrific meteor of 5th September, 1868, which broke into visibility
at an appalling height above the Black Sea, and had not expended
its stupendous energy until it passed over the smiling vineyards of
France.
Great fire-balls are much more numerous than any one would suppose
who had not paid attention to the subject. Nor need this be a
matter for surprise if it be remembered that when a fire-ball does
arrive it is only by a favorable combination of circumstances that
any particular individual is privileged to witness the exhibition.
As a random example of the yearly crop of fire-balls, I take from
the middle of 1877 to the middle of 1878. A list of the fire-balls
noticed during this period will be found in that store-house of
valuable information, the Reports of the British Association. In
the year referred to I see that eighty-six great fire-balls have
been recorded. They have appeared in various localities, both in the
old hemisphere and in the new. The most arduous observer may think
himself fortunate if he has even seen one of them.
As to the brilliant light from some of these great fire-balls, there
are numerous statements. We are not infrequently told that even the
beams of the full moon are ineffectual in comparison with the blaze
of the meteor; and we find a high authority asserting that one of
these bodies displayed a flash as “blinding as the sun.” On the
29th July, 1878, a fire-ball was seen which created so splendid an
illumination that “the smallest objects were visible at Manchester.”
Fortunate, indeed, would the astronomer have been who, guided by
some miraculous prescience, had gone to the ancient city of York on
the evening of the 23d of February, 1879, and on the tower of the
glorious minster spent the night in observation of the heavens. It
would have been his privilege to witness a majestic meteor under
circumstances of almost unique magnificence.
It was at seven minutes before three that such few stragglers as
the streets of York still contained saw a pear-shaped ball of fire
traveling across the sky. It drenched the ancient city with a flood
of light. The superb front of the minster never before glowed with a
more romantic illumination. The unwonted brilliancy streamed through
every aperture in every window in the city; every wakeful eye was
instantly on the alert; every light sleeper started up suddenly to
know what was the matter. Even those whom the blaze of midnight
light had failed to awaken were only permitted to protract their
slumbers for another minute and a half—only until an awful crash,
like a mighty peal of thunder, burst over the town, shaking the
doors, the windows, and even the houses themselves. The whole city
was thus alarmed. Every one started at the noise. But that noise was
not a clap of thunder. Nor was it produced by an earthquake. It was
merely the explosion of the fire-ball which flung itself against the
atmosphere after its immeasurable voyage through space.
Perhaps the most remarkable instance of the _explosion_ of a meteor
is recorded in the case of the great fire-ball so widely observed in
America on the 21st of December, 1876. The movements of this superb
object have been carefully studied by Professor H. A. Newton and
Professor D. Kirkwood. For the prodigious span of a thousand miles
this meteor tore over the American continent with a speed of some
ten or fifteen miles a second. It first appeared over Kansas at a
height of seventy-five miles. Thence it glided over the Mississippi,
over the Missouri; it passed to the south of Lake Michigan; it made a
short voyage over Lake Erie, and it can not have been very far from
the Falls of Niagara, when by becoming invisible all further traces
of its movements were lost. While passing a point midway between
Chicago and St. Louis a frightful explosion shivered the meteor into
a cluster of brilliant balls of fire, which seemed to chase each
other across the sky. This cluster must have been about forty miles
long and five miles wide. The detonation by which the explosion was
accompanied was a specially notable incident of this meteor. It was
not only heard with terrific intensity in the neighborhood, but the
volume of sound was borne to great distances.
The glory of a meteor is often so evanescent that we just get
a glimpse and it is gone. The sky resumes its ordinary aspect;
the familiar stars are there, and even the very situation of the
brilliant streak has become unrecognizable. But this is not always
so; it sometimes happens that the brief career of the meteor leaves
a notable trace behind it, so that for seconds and for minutes the
sky is diversified by an unwonted spectacle. The path of the meteor
leaves a stain of pearly light on the sky to mark the highway pursued
by our celestial visitor.
In its fearful career the meteor is often rent to fragments, reduced
to dust, dissolved into vapor. The glowing atoms of the wreck lie
strewn along the path, just as the ghastly remnants of Napoleon’s
mighty army limned out the awful retreat from Moscow.
A pencil-shaped cloud of meteoric débris, perhaps eighty or a hundred
miles in length, and four or five miles in diameter, thus hangs
poised in air. It is at night. The sun has sunk so far below the
horizon that there is no trace of the feeblest twilight glow. An
ordinary cloud would, of course, be invisible except as concealing
the stars; no beams of light fall upon it; there is nothing to render
it luminous. So, too, the meteoric streak will often pass instantly
into invisibility, but, as I have said, this is not always the case.
There is a well-authenticated instance in which the trail of a superb
meteor remained visible for nearly an hour. I have endeavored up to
the present to explain the various phenomena presented to us in the
fall of a meteor, but here, for the first time, we have to note a
circumstance for which it is not easy to account. We can explain why
it is that the long meteoric cloud should be there, but we can not
so easily explain why we should be able to see it. Whence comes this
beautiful pearly luminosity? It seems that the meteoric dust must
glow with some intrinsic luminosity.
We have spoken of dazzling fire-balls which generate for a brief
moment a light which eye-witnesses, with possibly a pardonable
exaggeration, have ventured to compare with the beams of the sun
himself. Other meteors are described as being as bright as the full
moon. Descending still lower in the scale of splendor, we read of
fire-balls as bright as Venus or Jupiter, as bright as Sirius, or as
a star of the first magnitude. With each step downward in brilliancy
we find the meteors to increase in numerical abundance. Shooting
stars as bright as the stars of the second or third magnitude are
comparatively frequent; they are still more numerous of the fourth
and fifth magnitudes. Every night brings its tale of shooting stars
whose brightness is just sufficient to impress the unaided eye. Nor
do the shooting stars which even the most attentive eye can detect
represent a fraction of their entire number. As there are telescopic
stars which the unaided eye can not see, so it might fairly be
conjectured that, as we can trace meteors of successive stages of
brightness down to the limit of unaided eye visibility, so there may
be meteors still and still smaller which would be detected could we
only direct a telescope toward them.
If we reflect that for every one that is seen there must be thousands
which dart in unseen, we obtain an imposing idea of the myriads of
shooting stars that daily rain in upon our globe.
The world is thus pelted on all sides day and night, year after year,
century after century, by troops and battalions of shooting stars
of every size, from objects not much larger than grains of sand up
to mighty masses which can only be expressed in tons. In the lapse
of ages our globe must thus be gradually growing by the everlasting
deposit of meteoric débris. Looking back through the vistas of time
past, it becomes impossible to estimate how much of the solid earth
may not owe its origin to this celestial source.
The first and most important truth with regard to the recurrence
of the meteors is their occasional appearance in what are known as
“meteoric showers.” During such displays it sometimes happens that
shooting stars in shoals break forth simultaneously, so as to produce
a spectacle which we now regard as of the utmost beauty and interest,
but which in earlier times has often been the source of the direst
terror and dismay.
Let me, for the sake of illustration, give some account of one of
these great showers of shooting stars.
In the year 1866 I occupied the position of astronomer to the late
Earl of Rosse. The memorable night between November 13th and 14th,
1866, was a very fine one; the moon was absent—a very important
consideration in regard to the effectiveness of the display. The
stars shone out clearly, and I was diligently examining some faint
nebulæ in the eye-piece of the great telescope, when a sudden
exclamation from the attendant caused me to look up from the
eye-piece just in time to catch a glimpse of a fine shooting star,
which, like a great sky-rocket, but without its accompanying noise,
shot across the sky over our heads. The great shooting star which had
already appeared was merely the herald announcing the advent of a
mighty host. At first the meteors came singly, and then, as the hours
wore on, they arrived in twos and in threes, in dozens, in scores,
in hundreds. Our work at the telescope was forsaken; we went to the
top of the castellated walls of the great telescope and abandoned
ourselves to the enjoyment of the gorgeous spectacle.
To number the meteors baffled all our arithmetic; while we strove
to count on the one side many of them hurried by on the other. The
vivid brilliance of the meteors was sharply contrasted with the
silence of their flight. We heard on that marvelous night no sounds
save those with which we were familiar. The flights of the celestial
rockets were attended with no noises that we could hear. The meteors
were no doubt somewhat various as to size, but the characteristic
feature of this shower, as contrasted with another great shower I
have also seen, was the remarkable brilliance of the shooting stars.
It was their exceptional splendor even more than their innumerable
profusion that gave to the shower its peculiarity. As to the actual
brilliancy of the meteors, I am enabled to give the accurate
estimate made by Mr. Baxendell at Manchester, where the shower was
well seen. Out of every hundred of these meteors ten were brighter
than a first magnitude star, and two or three of them were brighter
than Sirius. Fifteen out of each hundred were between the first and
second magnitudes, and twenty-five were between the second and third
magnitudes, while the remainder were smaller.
Some important facts with regard to ancient shooting-star showers
have survived the thousand and one casualties to which historical
records are exposed. A careful discussion of those which are
sufficiently accurate to be intelligible discloses to us the
startling fact that in general every thirty-three years a grand
shooting-star shower has rained down on our earth. It sometimes
happens that two consecutive years are rendered memorable by great
showers. At present the day of the year on which this particular
shower is wont to appear is about the 13th November; but in earlier
ages we find the date to shift slowly toward the commencement of the
year. Thus the display which took place in A. D. 1698 was on the 9th
of November; while, looking back still further to one of the very
earliest records, viz., that of the year 934, we find the date has
receded to October 14th. This change of the day on which the shower
occurs is of profound theoretical importance in connection with the
discovery of the orbit which these meteors pursue. The advance of the
date is, however, so slow that for the past few generations, as well
as for the next, we may sufficiently define this particular shower by
the meteors which enliven the skies between the 12th and the 14th of
November. In fact, the poetaster has parodied the well-known lines
for the days of the month by a similar effort, which will serve to
remind us also of another periodic shower of shooting stars which
occurs in August. He writes:
“If you November’s stars would see,
From twelfth to fourteenth watching be.
In August too stars shine from heaven,
On nights between nine and eleven.”
These lines are intended to imply that the days named will usually
bring, in every November, a few meteors at all events belonging to
the grand shower. These are stragglers, as it were, from the mighty
host which visits us three times in the century.
Astronomers have a special name for this group of November meteors.
They are called the “Leonids.” To explain why this name has been
given, and why it is appropriate, we must dwell on an important part
of the phenomena of the shower.
[Illustration: Fig. 23.—Position of Leo, Source of the Leonids]
Among the constellations there is a fine sickle-shaped group, forming
a part of Leo, one of the signs of the Zodiac. That part of the sky
defined by Leo is curiously related to the meteors of the 12th to
the 14th of November. Every shooting star truly belonging to that
great shower pursued a track across the heavens, the direction of
which, if carried back far enough, was always found to pierce through
the sickle of Leo. Indeed, the paths of all the meteors formed a set
of rays spreading away from that one point in the constellation. An
invariable characteristic of this particular shower is its connection
with the constellation of Leo, hence the appropriateness of the name
of Leonids.
It must be borne in mind that we can never see the meteors until the
fatal moment when they dive into our atmosphere. We could, indeed,
at any time point our telescope to the spot in the heavens where we
know the great shoal must certainly be located. But the mightiest
telescope in the world does not disclose the shoal to us. In fact,
we would never have seen these Leonids at all, we would never have
become conscious that such a shoal of meteors existed, had it
not been for a certain circumstance, which, for want of a better
expression, I must speak of as accidental.
Our globe pursues a certain definite track around the sun. Year after
year, with undeviating regularity, the earth performs the stages of
its journey. If it reaches certain points on the 1st of January and
the 12th of October in one year, then it reaches the same points on
the 1st of January and the 12th of October respectively on next year,
or any other year.
The Leonids and the earth have each a certain track. It might of
course have happened that one of these tracks lay quite outside or
quite inside the other. In the case of the Leonids, it has chanced
that their orbit does intersect the orbit of the earth, and to
this circumstance we are indebted for the glorious displays every
thirty-three years.
There are many other periodic showers of shooting stars besides those
notable Leonids. None of the other showers, however, possess the
same importance as the Leonids, nor do they ever manifest celestial
splendor comparable with that of those of the 13th of November.
The Perseids, for example, which appear from the 9th to the 11th
of August, are tolerably constant in their appearance, but have
little spectacular interest. There is also another shower called the
Andromedes, which occurs on the 27th of November. It has produced
certain displays, one of the most remarkable of which took place
in 1872. The meteors were excessively numerous on that occasion,
but they were so short in their paths, and so insignificant as to
brilliance, that the spectacle, though of great scientific interest,
could not be compared as to splendor with that of the Leonids in 1866.
There are also several other showers which appear with greater or
less regularity. Each of these possesses two distinct characteristics
by which its meteors can be identified. One of these characters is
the date on which the shower appears. The other is the constellation
or point on the heavens from which all the meteors appear to radiate.
Thus when we speak of the Andromedes on the 27th of November, we
express that the shower on the 27th November comes from the part of
the heavens marked by the constellation of Andromeda.
A striking discovery has been made which points to a curious
connection between comets and shooting stars. It has been found that
the track followed by a great shower of meteors is often identical
with the track pursued by a comet. It is wholly beyond the province
of mere chance that an orbit such as that of the Leonids should,
both as to its size and its position in space, be likewise that of a
comet, unless the comet and the meteor swarm were objects related to
each other.
The great sun guides our world through its long annual journey. The
mighty mass of the earth yields compliance to the potent sway of the
ruler of our system. But the sun does not merely exercise a control
over the vast planets which circulate around him. The supreme law
of gravitation constrains the veriest mote that ever floated in a
sunbeam, with the same unremitting care that it does the mightiest
of planets. Thus it is that each little meteor is guided in its
journeys for untold ages. Each of these little objects hurries along,
deflected at every moment, to follow its beautifully curved path by
the incessant attraction of the sun. At last, however, the fatal
plunge is taken. The long wanderings of the meteor have come to an
end and it vanishes in a streak of splendor.
COMETS.—SIR JOHN HERSCHEL