that it is rather surprising to find to how many intelligent people, a
second, as seen on the clock face, is its least conceivable interval.
Yet a second has not only a beginning, middle, and end, as much as a
year has, but can, in thought at least, be divided into just as many
numbered parts as a year can. Without entering on a disquisition about
this, let us try to show by some familiar thing that we can at any rate
not only divide a second in imagination into, let us say, a hundred
parts, but that we can observe distinctly what is happening in such a
short time, and make a picture of it,--a picture which shall be begun
and completed while this hundredth of a second lasts.
Every one has fallen through at least some such a little distance as
comes in jumping from a chair to the floor, and most of us, it is safe
to say, have a familiar impression of the fact that it takes, at any
rate, less than a second in such a case from the time the foot leaves
its first support till it touches the ground. Plainly, however large or
small the fall may be, each fraction of an inch of it must be passed
through in succession, and if we suppose the space to be divided,
for instance, into a hundred parts, we must divide in thought the
second into at least as many, since each little successive space was
traversed in its own little interval of time, and the whole together
did not make a second. We can even, as a matter of fact, very easily
calculate the time that it will take anything which has already fallen,
let us say one foot, to fall an inch more; and we find this, in the
supposed instance, to be almost exactly one one-hundredth of a second.
On page 243 is a reproduction of a photograph from Nature, of a man
falling freely through the air. He has dropped from the grasp of the
man above him, and has already fallen through some small distance,--a
foot or so. If we suppose it to be a foot, since we can see that the
man’s features are not blurred, as they would undoubtedly have been
had he moved even much less than an inch while this picture was being
taken, it follows, from what has been said, that the making of the
whole picture--landscape, spectators, and all--occupied not _over_ one
one-hundredth of a second.
We have given this view of “the falling man” because, rightly
understood, it thus carries internal evidence of the limit of time in
which it could have been made; and this will serve as an introduction
to another picture, where probably no one will dispute that the time
was still shorter, but where we cannot give the same kind of evidence
of the fact.
“Quick as lightning” is our common simile for anything occupying,
to ordinary sense, no time at all. Exact measurements show that the
electric spark does occupy a time, which is almost inconceivably small,
and of which we can only say here that the one one-hundredth of a
second we have just been considering is a long period by comparison
with the duration of the brightest portion of the light.
[Illustration: FIG. 92.--A FALLING MAN.]
On page 245 we have the photograph of a flash of lightning (which
proves to be several simultaneous flashes), taken last July from a
point on the Connecticut coast, and showing not only the vivid zigzag
streaks of the lightning itself, but something of the distant sea
view, and the masts of the coast survey schooner “Palinurus” in the
foreground, relieved against the sky. We are here concerned with this
interesting autograph of the lightning, only as an illustration of our
subject, and as proving the almost infinite sensitiveness of the recent
photographic processes; for there seems to be no limit to the briefness
of time in which, these can so act in some degree, whether the light be
bright or faint, and no known limit to the briefness of time required
for them to act _effectively_ if the light be bright enough.
What has just preceded will now help us to understand how it is that
photography also succeeds so well in the incomparably fainter objects
we are about to consider, and which have been produced not by short but
by long exposures. We have just seen how sensitive the modern plate
is, and we are next to notice a new and very important point in which
photographic action in general differs remarkably from that of the eye.
Seeing may be described, not wholly inaptly, as the recognition of a
series of brief successive photographs, taken by the optic lens on the
retina; but the important difference between seeing and photographing,
which we now ask attention to, is this: When the eye looks at a faint
object, such as the spectrum of a star, or at the still fainter nebula,
this, as we know, appears no brighter at the end of half an hour than
at the end of the first half-second. In other words, after a brief
fraction of a second, the visual effect does not sensibly accumulate.
But in the action of the photograph, on the contrary, the effect _does_
accumulate, and in the case of a weak light accumulates indefinitely.
It is owing to this precious property, that supposing (for illustration
merely) the lightning flash to have occupied the one-thousandth part
of a second in impressing itself on the plate, to get a nearly similar
effect from a continuous light one thousand times weaker, we have only
to expose the ¡date a thousand times as long, that is, for one second;
while from a light a million times weaker we should get the same
result by exposing it a million times as long, that is, for a thousand
seconds.
And now that we come to the stars, whose spectra occupy minutes in
taking, what we just considered will help us to understand how we can
advantageously thus pass from a thousandth of a second or less, to
one thousand seconds or even more, and how we can even,--given time
enough,--conceivably, be able to photograph what the eye _cannot see at
all_.
[Illustration: FIG. 93.--A FLASH OF LIGHTNING. (FROM A PHOTOGRAPH BY
DR. H. G. PIFFARD.)]
We have on page 231 a photograph quite recently taken at Cambridge from
a group of stars (the Pleiades) passing by the telescope. Every star
is caught as it goes, and presented, not in its ordinary appearance to
the eye, but by its spectrum. There is a general resemblance in these
spectra from the same cluster; while in other cases the spectra are
of all types and kinds, the essential distinction between individuals
alike to the eve, being more strikingly shown, as stars apparently
far away from one another are seen to have a common nature, and stars
looking close together (but which may be merely in line, and really far
apart) have often no resemblance; and so the whole procession passes
through the field of view, each individual leaving its own description.
This self-description will be better seen in the remarkable photographs
of the spectra of Vega and Aldebaran, which are reproduced on page 235
from the originals by a process independent of the graver. They were
obtained on the night of November 9, 1886, at Cambridge, as a part of
the work pursued by Professor Pickering, with means which have been
given from fitting hands, thus to form a memorial of the late Dr. Henry
Draper. We are obliged to the source indicated, then, for the ability
to show the reader here the latest, and as yet inedited, results in
this direction; and they are such as fully to justify the remark made
above, that minutes, by this new process, take the place of years of
work by the most skilful astronomer’s eye and hand.
The spectrum of Vega (Alpha Lyræ) is marked only by a few strong lines,
due chiefly to hydrogen, because these are all there are to be seen
in a star of its class. Aldebaran (the bright star in Taurus), on the
contrary, here announces itself as belonging to the family of our own
sun, a probably later type, and distinguished by solar-like lines in
its spectrum, which may be counted in the original photograph to the
number of over two hundred. There is necessarily some loss in the
printed reproduction; but is it not a wonderful thing, to be able to
look up, as the reader may do, to Aldebaran in the sky, and then down
upon the page before us, knowing that that remote, trembling speck of
light has by one of the latest developments of the New Astronomy been
made, without the intervention of the graver’s hand, to write its own
autograph record on the page before him?
In the department of nebular astronomy, photography has worked an equal
change. The writer well remembers the weeks he has himself spent in
drawing or attempting to draw nebulæ,--things often so ghost-like as
to disappear from view every time the eye turned from the white paper,
and only to be seen again when it had recovered its sensitiveness by
gazing into the darkness. The labors of weeks were, literally, only
represented by what looked like a stain on the paper; and no two
observers, however careful, could be sure that the change between
two drawings of a nebula at different dates was due to an alteration
in the thing itself, or in the eye or hand of the observer, though
unfortunately for the same reason it is impossible fully to render the
nebulous effect of the photograph in engraving. We cannot with our
best efforts, then, do full justice to the admirable one of Orion, on
page 239, which we owe to the particular kindness of Mr. Common, of
Ealing, England, whose work in this field is as yet unequalled. The
original enlargement measures nearly two square feet in area, with
fine definition. It is taken by thirty-nine minutes’ exposure, and its
character can only be indicated here; for it is not too much to say
here of this original also, that as many years of the life of the most
skilled artist could not produce so trustworthy a record of this wonder.
The writer remembers the interest with which he heard Dr. Draper,
not long before his lamented death, speak of the almost incredible
sensitiveness of these most recent photographic processes, and his
belief that we were fast approaching the time when we should photograph
what we could not even see. That time has now arrived. At Cambridge,
in Massachusetts, and at the Paris Observatory, by taking advantage
of the cumulative action we have referred to, and by long exposures,
photographs have recently been taken showing stars absolutely invisible
to the telescope, and enabling us to discover faint nebulæ whose
previous existence had not been suspected; and when we consider that an
hour’s exposure of a plate, now not only secures a fuller star-chart
than years of an astronomer’s labor, but a more exact one, that the
art is every month advancing perceptibly over the last, and that it is
already, as we may say, not only making pictures of what we see, but
of what we cannot see even with the telescope,--we have before us a
prospect whose possibilities no further words are needed to suggest.
We have now, not described, but only mentioned, some division of the
labors of the New Astronomy in its photometric, spectroscopic, and
photographic stellar researches, on each of which as many books, rather
than chapters, might be written, to give only what is novel and of
current interest. But these are themselves but a part of the modern
work that has overturned or modified almost every conception about the
stellar universe which was familiar to the last generation, or which
perhaps we were taught in our own youth.
* * * * *
In considering the results to be drawn from this glance we have taken
at some facts of modern observation, if it be asked, not only what
the facts are, but what lessons the facts themselves have to teach,
there is more than one answer, for the moral of a story depends on
the one who draws it, and we may look on our story of the heavens
from the point of view either of our own importance or of our own
insignificance. In the one case we behold the universe as a sort of
reflex of our own selves, mirroring in vast proportions of time and
space our own destiny; and even from this standpoint, one of the
lessons of our subject is surely that there is no permanence in any
created thing. When primitive man learned that with lapsing years the
oak withered and the very rock decayed, more slowly but as surely as
himself, he looked up to the stars as the types of contrast to the
change he shared, and fondly deemed them eternal; but now we have found
change there, and that probably the star clusters and the nebulæ, even
if clouds of suns and worlds, are fixed only by comparison with our own
brief years, and, tried by the terms of their own long existence, are
fleeting like ourselves.
“We have often witnessed the formation of a cloud in a serene
sky. A hazy point barely perceptible--a little wreath of mist
increases in volume and becomes darker and denser, until it
obscures a large portion of the heavens. It throws itself into
fantastic shapes, it gathers a glory from the sun, is borne
onward by the wind, and as it gradually came, so, perhaps, it
gradually disappears, melting away in the untroubled air. But the
universe is nothing more than such a cloud,--a cloud of suns and
worlds. Supremely grand though it may seem to us, to the infinite
and eternal intellect it is no more than a fleeting mist. If
there be a succession of worlds in infinite space, there is also
a succession of worlds in infinite time. As one after another
cloud replaces clouds in the skies, so this starry system, the
universe, is the successor of countless others that have preceded
it,--the predecessor of countless others that will follow.”
These impressions are strengthened rather than weakened when we come
back from the outer universe to our own little solar system; for
every process which we know, tends to the dissipation, or rather the
degradation, of heat, and seems to point, in our present knowledge, to
the final decay and extinction of the light of the world. In the words
of one of the most eminent living students of our subject, “The candle
of the sun is burning down, and, as far as we can see, must at last
reach the socket. Then will begin a total eclipse which will have no
end.
‘Dies iræ, dies illa,
Solvet sæclum in favilla.’”
Yet though it may well be that the fact itself here is true,
it is possible that we draw the moral to it, unawares, from an
unacknowledged satisfaction in the idea of the vastness of the funeral
pyre provided for such beings as ourselves, and that it is pride,
after all, which suggests the thought that when the sun of the human
race sets, the universe will be left tenantless, as a body from which
the soul has fled. Can we not bring ourselves to admit that there may
be something higher than man and more enduring than frail humanity,
in some sphere in which _our_ universe, conditioned as it is in space
and time, is itself embraced; and so distrust the conclusions of man’s
reason where they seem to flatter his pride?
May we not receive even the teachings of science, as to the “Laws of
Nature,” with the constant memory that all we know, even from science
itself, depends on our very limited sensations, our very limited
experience, and our still more limited power of conceiving anything for
which this experience has not prepared us?
* * * * *
I have read somewhere a story about a race of ephemeral insects who
live but an hour. To those who are born in the early morning the
sunrise is the time of youth. They die of old age while his beams are
yet gathering force, and only their descendants live on to midday;
while it is another race which sees the sun decline, from that which
saw him rise. Imagine the sun about to set, and the whole nation of
mites gathered under the shadow of some mushroom (to them ancient
as the sun itself) to hear what their wisest philosopher has to say
of the gloomy prospect. If I remember aright, he first told them
that, incredible as it might seem, there was not only a time in the
world’s youth when the mushroom itself was young, but that the sun in
those early ages was in the eastern, not in the western, sky. Since
then, he explained, the eyes of scientific ephemera had followed it,
and established by induction from vast experience the great “Law of
Nature,” that it moved only westward; and he showed that since it
was now nearing the western horizon, science herself pointed to the
conclusion that it was about to disappear forever, together with the
great race of ephemera for whom it was created.
What his hearers thought of this discourse I do not remember, but I
have heard that the sun rose again the next morning.
INDEX.
Abbe, Professor, 56.
Actinism, 71.
Adams, Professor, 195.
Africa, 116.
Ages, stellar, 238.
Air:
dancing, 17;
a medium, 33;
continuous, 176;
rarefied, 179;
motes, 181;
nimble, 191.
(See _Atmosphere_.)
Airless Mountains, 160.
Air-wave, 185.
Aitken’s Researches, 181.
Alaska, 38.
Aldebaran, 222, 235, 236, 246.
Algot, 228.
Allegheny Observatory, 17, 19, 84, 86.
(See _Langley_.)
Alphonsus Ring-plain, 156.
Alps, 39, 148, 151, 167, 181.
(See _Apennines, Lunar_.)
American Astronomers, 227.
American Continents, 20, 21, 31.
(See _South_.)
Andalusia, 53.
Animalculæ, 224.
Animals:
food, 74;
fright, 42.
(See _Dog_.)
Antares, 238.
Ants, 223.
(See _Insects_.)
Apennines, 151, 153, 155, 160, 167.
(See _Alps, Lunar_.)
Apples, 171.
Arab Traditions, 194.
(See _Moslem_.)
Arago, quoted, 41, 42.
Archimedes, 94.
Archimedes Crater, 151–153, 155.
Arctic Cold, 159.
Arctic Pole, 96.
Arcturus, 208, 211.
Aristillus Crater, 151.
Aristotelian Philosophy, 8.
Arzachel, 156, 161.
Asteroids, 128.
Astrology, 127.
Astronomers and Priests, 1–3.
(See _American, New_, _Old_.)
Astronomical Day, 85, 86.
Atmosphere, 136, 180;
as a shield, 216, 220.
(See _Air_.)
Atolls, 152.
Auger, simile, 31.
Aurora Borealis, 35, 67, 212.
Autolycus Crater, 151.
Axis, 9, 10.
Babel, 96.
Bain Telegraph, 88.
Balloons, 176.
Bees, 124.
(See _Insects_.)
Berkeley’s Theory, 70.
Berlin Observatory, 233.
Bernières’s Lens, 103.
Bessemer Steel, 104–108.
Birds, 172, 196, 197.
(See _Animals_.)
Black Hole, 73.
Bond, Professor, 204.
Boston, Mass., 88, 132.
Bothkamp, observations at, 66.
Breadstuffs, 78, 79.
(See _Grain_, _Sun-spots_, _Wheat_.)
Bridges, 20, 68.
Britain, Ancient, 1, 234.
(See _England_.)
British Isles, 14, 25.
Brocken Spectre, 55.
Brothers, Mr., 50.
Bubbles, 168.
Buffer, the air as a, 216, 220.
Bunsen’s Researches, 12.
Burnham, W. S., 233.
Burning-glasses, 102–104.
Burning Heat, 160, 163.
Cactus, 14, 24.
Calcutta, 73.
California, 151, 180.
Cambric Needle (_q. v._), experiment, 132.
Cambridge Observations, 227, 245–247.
Camera Obscura, 63.
Campanus Crater, 163, 165.
Candle, simile, 39.
Cannon-ball, 5, 38, 41, 98, 135, 186, 211.
Canopus, 234.
Carbon, 72, 73, 107, 221.
Carbonic-acid Gas, 219.
Carpenter’s Studio, 140.
Carrington’s Work, 79, 87.
Carthage, 116.
Cassini, 42.
Cassiopeia, 229.
Cataclysm, 30.
Centimetres, 93.
Chacornac’s Drawing, 33.
Chambers, on sun-spots, 80.
Charleston Earthquake (_q. v._), 42.
Chemical Elements, 221, 223.
Cherry-stone, comparison, 196.
Chicago:
great fire, 134;
astronomer, 233.
China:
lens, 103, 104;
soil, 180.
Chlorophyl, 73.
Chocolate, simile, 107.
Cholera, 80.
Chromosphere, 7;
clouds, 62;
forms, 64–68.
Cinders, 171.
Clark’s Glasses, 123.
Cliffs, 164.
Clock, 135.
Cloud-ocean, 179.
Clouds:
cirrous, 27, 28;
beautiful, 54;
and rain, 111;
formed, 249.
Coal-beds, 115.
Coal:
energy, 73–75, 111;
destroyed, 97;
wasted, 101;
stock, 112.
Cobweb, simile, 26.
Cold:
and eclipses, 40;
in planets, 136.
Colorado, 50.
Colors:
in eclipses (_q. v._), 65;
mental, 70, 71;
in Jupiter (_q. v._), 127;
in moon (_q. v._), 168;
in stars (_q. v._), 227;
spectrum (_q. v._), 236.
Comet-hunters, 204, 207.
Comets:
chapter, 199–220;
Donati’s, 201, 204, 205, 207, 209, 217;
one part, 203;
parts and name, 208;
tail (_q. v._), 208, 211;
diameter and parts, 216;
spectroscope, elements, dread, 219;
numerous, stone, 219, 220;
kernel, 220;
(1858), 213–216;
(1866), 200.
Common, A. A., 239, 247.
Compass, 86.
Connecticut Observations, 186, 242.
Converter, 104–108.
Coral, 151.
Corn, 111.
(See _Grain_.)
Corona, 7, 36, 37, 40, 41, 43, 45–52, 55, 56, 59, 60–62.
Cotton-mill, 74.
Counting, 94.
Cracks, celestial, 163.
Craters, 164.
(See special names.)
Crystalline Structure, 4, 23–27.
Cyclones, 24, 31, 32, 68.
Decay, 248, 249.
Delambre’s History, 207.
De la Rue’s Engraving, 125.
Delfthaven, 5.
Denning’s Theory, 197.
Diamonds, melted, 103.
Dies Iræ, 249.
Dipper, 207, 208.
(See _Great Bear_, _Polar_.)
Diurnal Oscillation, 87.
Dog, anecdote of, 42.
(See _Animals_.)
Donati, 201, 204, 205, 207, 209, 213, 217.
(See _Comets_.)
Double Stars, 233.
Draper, Professor Henry, 128, 246, 247.
Ducks, noise, 188.
Dust, 34, 100, 101, 102, 105, 197.
Dynamite, 182, 185, 220.
Earth:
relations, 3, 4;
description difficult, 6;
temperature (_q. v._), 34, 101;
a string of earths, 96;
stars like, 118;
seen from outside, 133–135;
craters, 148.
Earthquakes, 220.
(See _Charleston_.)
Earth-shine, 167, 172.
Eclipses:
total, 7, 37;
screen, 36;
three, 39, 55;
partial, 40;
singular gloom, 39–43;
causing fright, 43;
colors (_q. v._), 48, 56, 61, 65, 66;
(1842), 41;
(1857), 48;
(1869), 39, 40;
(1870), 44, 61;
(1871), 50, 66, 68;
(1878), 38, 50, 57, 58.
(See _Total_.)
Egypt, 116, 234.
(See _Pyramids_.)
Electricity, 13, 75, 76.
Electric Light, 7.
Electric Spark, 242.
(See _Lightning_.)
Electric Storm, 84, 85, 88.
Elizabeth, Queen, 115.
Engine-power, 98, 111.
England:
fleets, 2;
coal, 115.
(See _Britain_, _London_.)
Engraving, 17.
Enigma, 228.
Ephemera, 250, 251.
Equatorial Landscape, 13, 17, 18, 47.
Equatorial Telescope, 122.
Ericsson:
engravings, 112, 113;
discoveries, 163.
Eruptive Promontories, 66–68.
Etna, 164, 181.
Europe, size, 25.
Evolution, planetary, 139.
Explosive Forces, 182–194.
Eye, 71, 227.
Eye-pieces, 47, 63.
Fabricius’s Observations, 8.
Fact and Fancy, 175.
Factory, 73.
Faculæ, 32, 33.
Falling, 242, 243.
Falling Stars, 193.
(See _Meteors_, _Shooting_.)
Faraday, Michael, 76.
Fault, technical term, 156.
Faust, 139.
Faye:
theory, 29–32;
on Comets’ Tails, 212.
Fern-like Forms, 25, 26.
Filaments, 25–27, 30, 55, 56, 65, 66, 68.
Fire, in sun (_q. v._), 92.
(See _Flames_, _Heat_.)
Fixed Stars, 233.
Flame-like Appearances, 23, 24.
Flames, 65, 66, 69, 185.
Flashes, 189, 195.
Flax, 111.
Flowers, color (_q. v._), 70.
(See _Rose_, _Plants_.)
Foliage-forms, 32.
Fontenelle’s Story, 133.
Forbes’s Observations, 38, 39.
Frankenstein, 221.
Franklin’s Discoveries, 76.
Fraunhofer Studies, 235.
French Institute, 186.
Frost-crystals (_q. v._), 23.
Furnaces, 101.
Galileo, 8, 121–123, 139, 140.
Gas:
glowing, 44;
in sun, 60.
Gas-jets, 40, 61, 68, 88.
Gassendi’s View, 172, 173.
Gelinck’s Observations, 80.
Geminids, 196.
Genii, 193.
Geographers and Geologists, 133.
Glare, 14, 18, 62–64.
Glass:
spun, 26;
globe, 145.
Glow-worms, 7, 117.
Good Hope Observations, 80.
Gould’s Researches, 80.
Grain, prices, 77, 80, 87.
(See _Corn_, _Sun-spots_, _Wheat_.)
Gramarye, 92.
Grass-blades, 66, 72.
Grasses, 26.
Gravitation, 72, 203;
negative, 215.
Great Bear, 207.
(See _Dipper_, _Polar_.)
Green’s Maps, 130.
Greenwich Observatory, 2, 81, 82, 84, 85, 88, 89.
Gulliver’s Travels, 131, 132.
(See _Swift_.)
Gunpowder, 186.
Guns, 135.
(See _Cannon-ball_.)
Hall Island, 130.
Hall, Professor, 131.
Hand, illustration, 168.
Harkness’s Observations, 44.
Harvests, 90.
Hastings, Professor, 60.
Heat:
development, 13;
concentration, 19;
loss, 29;
confinement, 33;
sensation, 71;
vibrations, 72;
energy, 91;
amount, 92, 97;
computation, 94–96;
diminution, 101;
emission, 102;
storage, 111;
in sugar, 188.
(See _Flames_, _Sun_.)
Hecla, 164, 181.
Hedgehog-spines, simile, 68.
Helmholtz’s Estimates, 98.
Hengist and Horsa, 1.
(See _Britain_.)
Hercules, 238.
Herschel, Sir John:
sun-spots, 12–14;
electric storms, 88;
comet’s tail, 216.
Herschel, Sir William:
avoidance of light, 18;
prices, 79;
sun-spots (_q. v._), 129.
Herschel’s Outlines, 11.
Holden, Professor, 124.
Honeycomb Structure, 30.
Huggins’s Experiment, 234, 235.
Humanity, deified, 172.
Human Race, 250.
Humboldt, 195.
Humming-bird, 70.
Hunt, Professor, 136, 219.
Hydrogen, 68, 99, 237.
Ibrahim, King, story, 194, 195.
Ice:
melted, 95, 96;
never melted, 163, 164.
Imbrian Sea, 151.
Insects, 224, 250.
(See _Ants_, _Bees_.)
Iron:
melting, 19, 107;
appearance of cold, 25;
in sun, 28;
in man, 221;
in stars, 236, 237.
(See _Steel_.)
Ironstone, 188.
Ivy, 115.
Janssen’s Observations, 61.
Jevons, Professor, 80.
Joseph in Egypt, 90.
Jumping, 241, 242.
Jupiter, 79, 118, 124, 127–129, 156, 185, 229.
Kensington Museum, 221.
Kepler, on Comets, 219.