THE FINAL QUESTION
In passing in review the various members of the solar system, it has been
seen that there are many conditions that have to be fulfilled before a
planet can be regarded as the possible abode of life, because there are
many conditions necessary in order that water may exist on its surface in
the liquid state. The size and mass of the planet are restricted within
quite narrow limits; and a world much larger or much smaller than our own
is necessarily excluded. The supply of light and heat received from the
Sun must not fall much below that received by the Earth, nor greatly
exceed it; in other words, the distance of the planet from its Sun is
somewhat precisely fixed, since the light and heat vary inversely not as
the distance, but as its square. Of course, in different systems, with
suns of different power, the most favourable distance will not be the same
in each; but in any system there will be one most advantageous distance,
and no great departure from it will be possible. This condition further
implies that the planetary orbits must be nearly circular; pronounced
eccentricity, such as the orbits of even our short-period comets display,
would be fatal to the persistence of water in the liquid state, and hence
to the continuance of life. A wide discordance between the planes of the
planet's equator and of its orbit, by rendering the seasons extravagantly
diverse, would act as prejudicially as an eccentric orbit, and a rotation
period equal to that of revolution would mean that one hemisphere was
eternally frozen while the other was exposed to perpetual heat.
It follows that in any given system there can be at most only one or two
planets upon which life can find a home, and this only where the right
conditions of size and mass, of rotation period, inclination of axis, and
shape of orbit, all co-exist in a globe at the proper distance. But the
type of system offered by our Sun and his planets is not the only one that
exists. A very large proportion of stars are binaries--two suns revolve
round their common centre of gravity. In many cases the two suns are
separable in the telescope, and their relative movements can be measured;
in other cases, termed "spectroscopic binaries," we only learn that a star
which appears absolutely single has two components from the evidence of
its spectrum; the spectroscope revealing two sets of lines that vibrate to
and fro with respect to each other. Yet, again, a third class of double
stars has made itself known in the "Algol variables." The optical double
stars are cases where the two components are far distant from each other,
and hence can be distinguished in our telescopes as separate points of
light. The "spectroscopic binaries" are cases where the two components are
too close to be separately perceived, but where the two are not greatly
unequal in brightness, so that the spectrum of the one does not overpower
that of the other. The "Algol variables" are cases where the two
components are of very unequal brightness, and, being very close to each
other, are so placed with respect to the Earth that the fainter partly
eclipses the brighter in its revolution round it, and so causes a
temporary diminution in its light at regular intervals. All these three
classes of binary systems are now known to be very numerous. Prof.
Campbell estimates that fully one star in six is a spectroscopic binary.
But there must be many binary systems that do not reveal
themselves--double stars where the companion is too faint or too close to
be detected, Algol systems where the companion does not pass before its
primary--and it seems almost certain that simple systems, like that of
which our Sun is the unchallenged autocrat, must be comparatively rare.
But the problem of the movements of a planet attendant upon two or more
suns is one of amazing complexity, and our greatest mathematicians have as
yet only been able to deal with the approximate solution of a few very
special cases. These are, however, sufficient to show that the orbit of a
planet so placed would be most irregular; the variations in the supplies
of light and heat received would be as great as even comets experience
within the solar system, and, what would be more disastrous still, these
variations would not be periodic but irregular. One year would be unlike
that which preceded it, and would be followed by changed conditions in the
next. Plants and animals would never have the chance of acclimatizing
themselves to these ever-changing vicissitudes. The stability of condition
essential for the maintenance of water in a liquid state would be wanting;
and, in consequence, Life could neither come into existence, nor persist
if it once appeared.
So far, therefore, our line of thought has led us to recognize that Life
can exist in comparatively few of the innumerable stellar systems strewn
through infinite space, and in any given system it can at best find only
one or two homes. The conditions for a Life-bearing planet are thus both
numerous and stringent--there is no elasticity about them. It is not
sufficient that a planet might fulfil many or even most of these
conditions; failure in one is failure altogether; "one black ball
excludes;" the candidate who fails in a single subject is "ploughed"
without mercy. And in most cases the failure is final; no opportunity is
given to the candidate to "sit" again.
But Space is not the only horizon along which our thought must be
directed; there is also the horizon of Time. Every world must have its
Past and its Future, as well as its Present. For some worlds the
conditions are so fixed that, like Jupiter and Saturn, they are not now
worlds that can be dwelt in, they never were in that condition, and they
never can be; their enormous mass forbids it. Mercury and the Moon at the
other end of the planetary scale are also permanently disabled; their
insignificant size excludes them. There was also a time when the Earth was
not a world of habitation; it was "without form and void"; hot and
vaporous, even as the four outer planets are now. Now it is inhabited, but
there may come a time when this phase of its history has run its course,
and either from a falling off in the tribute of light and heat rendered to
it by the Sun, or from the gradual desiccation of the surface, or,
perchance, from the slow loss of its atmosphere, it may approach the
condition of Mars, and in its turn be no longer an abode of life. Many
planets are essentially debarred from ever entering on the vital stage;
but of those to which such a stage is possible, it can only form an
incident in the entire duration of the orb. And if our Earth is any type
or example of the vital stage in general, vast aeons must run their course
from the first appearance of the humblest germs of life up to the bringing
forth of Life in conscious Intelligence. One hundred million years are
freely spoken of in this connection by those who study the crust of the
Earth and those who are occupied with the relations of the varied forms of
life. Man is the latest arrival on this planet, and however far back we
try to push the time of his earliest appearance, it is beyond question
that that time, relatively to the entire duration of the Earth since a
solid crust began to form, is but as yesterday. If, from some other globe
in the depths of space, this world of ours could have been watched during
the long aeons that elapsed from its first separation from the solar
nebula down to the time when it first possessed a surface of land and
water, and from that time, again, throughout the hypothetical one hundred
million years that preceded the advent of man, then, during all those
aeons, those imagined observers would have had under their scrutiny a
world as yet without inhabitant. The Earth now is in the inhabited
condition, but science gives us no clue as to how long that condition will
endure; rather such hints as are afforded us would seem to point to its
lasting but for a brief season as compared with the indefinite duration
which preceded it, and the indefinite duration which shall follow.
If this thought be sound, it places before us an entirely new and most
serious consideration. The world predestined for habitation must not only
have its size within certain narrow limits, its distance from its central
sun in a certain narrow zone, its rotation period, the inclination of its
axis, the eccentricity of its orbit, all suitable alike, but even if in
these and in all other necessaries it is perfectly adapted for habitation,
yet it will be only during a relatively small fraction of its entire
duration that Intelligent Life, clothed in material form, will find a
place upon it.
Let us sum shortly what we know and what we conclude. We know that this,
our Earth, is a habitable globe, for we ourselves are living upon it. We
know what constitutes the physical basis of our life, and under what
conditions on this Earth it flourishes, and under what conditions it is
destroyed. If we turn our eyes from this, our Earth, and look out upon the
starry skies, we see the other planets of our system, and the suns which
are the centres of other systems. From the consideration of the planets in
our own system, we have seen how stringent and how many are the conditions
imposed for Life to be possible. Round our Sun there is but a narrow zone
in which a habitable world may circle; in this zone there is room for but
few worlds, and we actually know of three alone, the Earth, the Moon, and
Venus. We know that the Earth can be and is inhabited; that the Moon is
not and cannot be inhabited; and that Venus, though of habitable size, may
yet be subject to the fatal disqualification of always turning the same
face to the Sun. Of other planetary systems than our own, we actually know
of none, but we assume that there are such, and as numerous as there are
suns in the starry depths. But of these planetary systems we can rule out,
as containing no habitable member, all such as circle round double or
multiple suns or, indeed, round any single star that, from whatever cause,
is largely variable and, therefore, much less stable than our own. Mira
Ceti, which in 5 months increases its brightness 1000 times, may stand as
an example. Probably these disqualifications rule out of court the great
proportion of the stellar systems. Of the few, comparatively speaking,
single and stable suns that remain in the heavenly abyss, we must
conclude, from what we know of our solar system, that they, too, have but
a narrow zone, outside of which no world would be fit to dwell in; whilst
in the zone the few worlds which might exist must violate no one of many
strict conditions. If we assume that there are a hundred million stars
within the ken of our telescopes, we may well believe that not more than
one in a hundred of these would fulfil the condition of being a single and
stable sun, such as ours. Of the planets revolving round these million
suns--stable and efficient suns--can we expect that in more cases than one
in a hundred there will be a planet in the habitable zone fulfilling all
the other conditions of habitability, of size, mass, inclination of axis,
circular orbit, and rotation? Of these ten thousand earths which may be
made fit for the habitation of Man, can we assume that even one in a
hundred is now at that epoch in its history when it is no longer "without
form and void," when a division has been made between the waters under the
firmament and those that are above the firmament; when the waters under
the heaven have been gathered into one place, and the dry land has
appeared, and when the earth and the waters have brought forth life
abundantly? Out of a hundred million of planetary systems throughout the
depths of space, can we suppose that there are even one hundred worlds
that are actually inhabited at the present moment? These numbers and
proportions certainly are not, and cannot be, based on knowledge; they are
given as illustrations only; but, vague as they are, they suggest that our
Earth may be neither one of many inhabited earths, nor yet unique, but one
of a few--indeed of a very few.
And then the objection is raised: "If our own Earth is but one of,
perhaps, two inhabited worlds in the solar system; and of perhaps one or
two hundred inhabited worlds throughout the furthest space that we can
scan; why is all this waste?" Of all the countless millions of stellar
systems without living organisms as inhabitants, we cannot tell the
purpose for the simple reason that we do not know it; but of "waste" in
the solar system, there is no question. Relatively speaking, this is quite
insignificant, for we cannot consider that as "waste material" which is
useful and, indeed, essential to existence. For, consider first the
material in the Earth itself. Its total volume is 260,613,000,000 cubic
miles, but man only lives _upon_ its surface of less than 200 million
square miles in extent, and he can not probe down as far as ten miles
below it, through the depths of ocean or by his deepest mine. Thus we are
left with over 258 thousand million of cubic miles that man, or plant, or
beast can never make direct use of. But without this 258 thousand million
cubic miles that he can never sow nor reap, the overlying platform on
which he dwells would be useless for retaining the air or the water by
which he lives. No less essential is the Sun; its vast bulk of
2,000,000,000,000,000,000,000,000,000 tons
can, in no single unit, be counted "waste," for it is from this that the
heat and light necessary for life on the Earth is derived. But the tonnage
of all the planets combined is but 0.13 per cent of the Sun alone; and a
wastage, if such it is, like this is insignificant from a material point
of view.
There is a type of politician at the present day who is convinced that the
highest purpose to which land can be put is to build upon it; that being,
in general, the use giving the highest money return per square foot,
though the return does not always fall to the builder. It has taken not a
little agitation and popular pressure to enforce the truth that cultivated
land is also of use. But there are few who realize that land that is
neither built upon nor cultivated is also essential. Our barren moors and
bleak hillsides, "wastelands" as we call them, are absolutely necessary as
collectors of the water by which we live. From them our springs take their
source; and they supply our cities with the first necessity of life.
We find, then, in this universe so far as we can know it, that Space is
lavishly provided, Matter is lavishly scattered, Time is unsparingly drawn
upon, but Life in any form, and especially in its highest form, is,
relatively speaking, very sparsely given. That very circumstance surely
points to the overwhelming importance of conscious, intelligent Life, and
the insignificance of lifeless matter in comparison with it. We have to
exhaust arithmetic in computing the size, the mass, the output of heat and
light of our Sun, yet it is but the hearth-fire and lamp of terrestrial
life; and its amazing agglomeration of matter and energy is ungrudgingly
devoted to this humble purpose. Whatever view we hold as to the scheme of
the universe; whether with the unthinking we fail to recognize Thought and
Purpose behind its marvellous manifestations, or, with the thoughtful,
realize that only Infinite Thought could provide so wonderfully for the
bringing forth of thought in living material organisms, the conclusion
still remains: living intelligences are, by the direct testimony of the
universe itself, its noblest and most precious product.
The plea is often made that as we find life adapting itself to a great
variety of conditions on this Earth, we must not set limits to its power
of adaption to the conditions of other worlds. But this plea is an
unthinking one. The range of conditions through which we find life on this
Earth is as nothing to the range given by the varied sizes and positions
of the different planets; and even on our Earth, life in the unfavoured
regions--the tops of mountains, the polar snows, the waterless deserts,
the ocean depths--is only possible because there are more favoured regions
close at hand, and there are, as it were, "crumbs that fall from the rich
man's table." A well-known litterateur in setting forth "a hundred ways of
making money" gave great prominence to the method of living as caretaker
in an empty house. But residing in an empty house does not, in itself,
supply the means of sustenance; these have to be furnished by the
wealthier man who employs the caretaker.
Another plea for vague sentiment in this matter is that we cannot expect
that intelligent beings on other worlds would have the same form as man,
and if not the same form, then, that the same conditions of existence
would not hold good for them as for us. Both contentions are unsound.
Protoplasm is the physical basis of all the life that we know, whatever
its form; though these forms are to be counted by the million, and are as
diverse as they are numerous. And everywhere and always, water is found
essential to protoplasmic life. Of life of any other kind we do not know
any examples; we have no instance; if such exist, then they are beyond our
ken.
And neither anthropologist nor biologist would admit that the form of
intelligent life was an unrelated accident. Whether the form brought the
intelligence, or the intelligence the form, or both were evolved together,
the one reacting on the other, the human form and the human intelligence
are associated, and we feel this to be so of necessity. In 1891, Dr.
Eugene Dubois found in Java a molar tooth and a portion of a skull, and
later the thigh bone of the left leg, and two more teeth. Such as they
were, these relics appeared nearer in form to the corresponding fragments
of an average Australian than to those of an ape, and on this ground
intelligence was claimed for the creature of which they were the remains,
and it was given the name of Pithecanthropus, or Ape-Man. The discovery
aroused much discussion, but on all sides it was unhesitatingly assumed
that the difference between the form of Pithecanthropus and that of the
most similar ape was an index of its superior intelligence over the ape,
just in so far as that difference was in the direction of the modern human
form. The same remark applies to the recent discovery of very ancient
human remains in Sussex. Never at any time has it been supposed that the
physical frame has followed any other path in the evolution of
intelligence than that which brought forth man. The flesh-eating animals
have attained efficiency in hunting and warfare by variation along many
types of form; the herbivora have been not less varied in the forms by
which as races they secured themselves from destruction; but Thought has
been associated with the development of one type or form only, and the
entire future of Thought on this planet rested neither with mammoth nor
cave-bear, but with the possessor of the erect stature, the upward look,
the differentiation of hand and foot, even in their crudest and earliest
stages.
Swift, in _Gulliver's Travels_, conceived of a land where the intelligence
and conscience of Man dwelt in the form of the horse, and the human form
tabernacled the instincts of the beast. H. G. Wells, in his _War of the
Worlds_, attributed intelligence to monsters--half-cuttlefish and
half-anemone,--and the human form to their helpless, unresisting prey.
Both conceptions are as scientifically absurd as they are gross and
revolting; and if it were possible for the skeleton of creatures from
other worlds to be brought to us here, then biologists would as
confidently pronounce on their intelligence as they do on the extinct
forms of bygone ages--the nearer to the human form, the nearer to the
human mind. We have found the figures of reindeer, horse, and mammoth
scratched in outline on a mammoth tusk; but though the artist has left no
other trace, we need no further evidence of his bodily form. Neither
horse, nor reindeer, nor mammoth made those rough outlines; they were
drawn by a man. More striking still, France yields us chipped flints by
the million, flints so slightly shaped that it is in dispute whether they
may not have been so broken by the action of torrents. But there are only
two theories about them; either they were so chipped by natural action, or
they were designedly so chipped by creatures resembling ourselves in head
and hand.
The question that has been dealt with in this volume is a scientific one,
and the attempt has been made to treat it as such, and to argue from known
physical facts as to the conditions of worlds which we cannot visit. But
by many the question is generally discussed wholly apart from physical
facts at all, and it becomes one of sentiment and of religious sympathy.
Yet, curiously enough, the division between those who think that all
worlds must be inhabited and those who think that our own world stands
alone is not coincident with any line of theological divisions, but rather
cuts across all such. Some believers in Christianity argue that since God
has filled this world with Life, Life has been His purpose in the world,
and must therefore have been His purpose in all other worlds--they too
must be filled with Life in like manner. Other believers argue that this
world was the scene of the Incarnation of Our Lord, and is therefore
unique in that respect; and that this uniqueness sets its stamp upon this
world in all respects. Opponents to Christianity are divided into the same
two classes, the one arguing that wherever there is matter the inevitable
course of evolution will produce life, and eventually intelligent life.
The other class are equally clear that all forms of life are special, the
result of the particular environment, and that it is unreasonable to
expect that any other world has had the same history as our own, or that
the same special conditions have prevailed elsewhere. In other words the
belief that there are other inhabited worlds has depended chiefly neither
on science nor on religious belief, but upon sentiment. There are some who
like to think themselves, and the race to which they belong, altogether
exceptional; others delight in finding themselves reflected wherever they
look. So far as Science has progressed and can return an answer to an
enquiry that exceeds so far the bounds of our direct observation, it
dissents from both orders of thought. The conditions of life are indeed
narrow, special, restricted; intelligent, organic life must, relatively
speaking, be a rarity in the universe, but we lack the information that
would enable us to affirm with any confidence that such life is only to be
found upon this world of ours. Heavy as the odds are against any
particular world being an inhabited one, yet when the limitless extent of
space is considered, and the innumerable numbers of stars and systems of
stars, it seems but reasonable to conclude that though inhabited worlds
are relatively rare, the absolute number of them may be considerable;
considerable, if not at one particular moment of time, yet when the whole
duration of the universe is admitted.
But there is a religious question connected with this enquiry; one that
goes down to the very roots of man's deepest thoughts and aspirations. As
individuals our days on the Earth are as a shadow, and there is none
abiding; as individuals we pass and disappear; and though the race
remains, yet as far as science can guide us and enable us to penetrate the
future, the same lot awaits the race as well. Slowly but surely the water
of a planet will combine with its substance or disappear into its crust.
The cooling of the Sun, though it may be long delayed, would seem to be
inevitable in the sequel.
"Oh, life as futile then as frail.
* * * *
What hope of answer or redress?
Behind the veil, behind the veil."
It is to this veil that we are now brought. It seems impossible to believe
that Life, so rare a fruit of the universe, intelligent Life, conscious
Life, to which the long course of evolution has been so manifestly leading
up all through the long ages, should have no better destiny than a final
and hopeless extinction; that this Earth and all the efforts and
aspirations of the long generations of men should have no worthier end
than to swing, throughout the eternal ages, an empty, frozen heap of dust,
circling round the extinct cinder that was once its Sun. If we look
backward, we seem to discern clear signs of progress; if we look forward,
we discern nothing but the veil. Science is but organized experience, and
experience of the future we have none.
There was a time when on this world there was no life; a time when life
began. How did it begin? Under what conditions?
Of that great change--when non-living matter first became endowed with
life, became so endowed not by the action and intervention of other living
matter, but without it--we have no knowledge, no experience. And so long
as this continues to be the case, that change, the greatest physical
change that has yet taken place in the history of the universe, the first
change of the non-living into the living, is outside the reach of science;
it lies beyond its border. We may guess and speculate about it, but
speculation is not science; we may spin words about it with the utmost
skill of the dialectician, but metaphysics is not science; it can never
come within the scope of science until it has first come within the scope
of experience.
There is, therefore, a veil behind us as well as the one that encloses us
in front; and as hitherto Science has failed to pierce the veil of the
past, it is even less able to pierce the veil of the future; for of the
future we have no experience.
* * * * *
Here, then, our enquiry must end, for it is an enquiry of physical
science; the search for living material organisms endowed with
intelligence. How life first came upon this Earth, or when, or where, is
beyond the power of science to determine. Yet it did come. There was a
time when there was no life here; none, not even the humblest form of it;
nor was there any hint or foreshadowing of it, still less of all its
infinities of form, and possibilities of development.
Once Life was not, yet Life came, and now, life is abundant, but abundant
only in worlds quite exceptional in their conditions, and therefore few in
number; it is even conceivable that this Earth of ours may be unique. But
life as we know it, protoplasmic life, life dependent upon water, the life
of intelligence united to the material organism, is under sentence of
death. Has it any future beyond that veil? Is there any kind of life not
subject to these narrow limitations; not under the inexorable decree?
To questions such as these Science has no reply to give; it is even more
helpless to answer them than to determine how life first came; its
experience does not reach so far. Science can examine the present
conditions of physical life, but whether or no that life can undergo a
change greater than that which passed upon the old inorganic world, it
cannot determine. It has no experience.
But if Science is dumb, if the utmost exertion of human energy and power
of research can throw no light on a future of which we have no experience,
we are not left without an answer. A voice has been heard, the voice of
the Son of God Himself:
"I am the Resurrection and the Life. He that believeth on Me, though he
were dead, yet shall he live."
And accepting His word, the Church in all ages, and among all nations,
peoples, and tongues, has made reply:
"I LOOK FOR THE RESURRECTION OF THE DEAD AND THE LIFE OF THE WORLD TO
COME."
INDEX
Abbot, C. G., 27, 34
Albedo of Earth, 54, 81
---- Jupiter, 127
---- Mars, 81
---- Moon, 54
_Albumin sol_, 15
Algol-type stars, 35, 144, 145
Antares, 38
Antoniadi, E. M., 97, 104
Archangel, climate of, 87, 88
Arcturus, 35, 37
Aristarchus, lunar crater, 48
"Astronomical unit," 21
Atmosphere of, Mars, 76
----, Moon, 53
----, Sun, 25
----, Venus, 112
Barnard, E. E., 89, 104
Beer, 60, 97, 98
Bond, G. P., 127, 128
Brewster, Sir David, 4
Calcium, 12, 36
Callisto, satellite of Jupiter, 131
Calory, 26
Campbell, W. W., 145
Carbon, 11, 34, 38, 39
Carbonic acid, 11
Cassini, 59, 60, 130
Ceres, minor planet, 41, 120, 121, 122, 131
Cerulli, V., 104, 108
Chromosphere, 28, 29
Cobalt, 33
Comet, Encke's, 119
----, Halley's, 119
----, spectra, 38
Copernican theory, 1
Copper, 33
Corona, 40
Coxwell, 25, 75, 79
Cyanogen, 37, 38
Czapek, F., 11, 13
Darwin, Sir G. H., 116
Dawes, W. R., 60, 63, 97, 99
Denning, W. F., 104
Dispersion, anomalous, 28
Doppelmayer, lunar crater, 52
Dubois, Eugene, 155
Eros, minor planet, 57
Europa, satellite of Jupiter, 131
Evans, J. E., 107
Faculae, 29, 30
Fauth, P., 50
Flamsteed, lunar crater, 52
Fluorine, 40
Fraunhofer, 33
Galileo, 51, 59, 131
Ganymede, satellite of Jupiter, 131, 132
Gay-Lussac, 75
Glaisher, J., 25, 75, 79
Goodacre, W., 49
Green, N. E., 60, 62, 63
Greenwich Hospital School, 107, 108
"Gulliver's Travels," 82, 156
Haeckel, E., 12
Halogens, 36, 40
"Harper's Weekly," 93
Helium, 37
Herschel, Sir J., 54
---- Sir W., 20, 49, 59, 60, 61
Hevelius, 51
Hippalus, lunar crater, 52
Hooke, R., 59, 60, 130
Huyghens, 59
Hydrocarbons, 38
Hydrogen, 11, 36, 37, 38, 41, 81
"Inhabitant," 5
"Inhabited" Worlds, 2, 3, 4
Io, satellite of Jupiter, 131
Iron, 12, 33, 36
Jupiter, 122-32
----, belts, 127, 129
----, great red spot, 130
----, proper motion of spots, 129
----, satellites of, 128, 131
----, white spots, 128, 130
Keeler, J. E., 122, 125
Kies, lunar crater, 52
Kirchhoff, 33
Lacus Solis, 97, 98, 99
Langley, S. P., 55
Lilliputians, 82, 83
Linne, lunar crater, 48
Lockyer, J. N., 60
Lowell, P., 65, 66, 67, 69, 71, 81, 97, 98, 99, 101, 103, 104, 105, 106,
108, 109, 110
Lucifer, 111
Maedler, 46, 48, 60, 97, 98
Maginus, lunar crater, 46
Magnesium, 12, 36
Manganese, 33
Mare Fecunditatis, 47
---- Humerum, 52
---- Nubium, 52
---- Serenitatis, 48
Mars, canals of, 57-70, 78, 101, 102
----, conditions of, 71-95
----, illusions of, 96-110
----, meteorology of, 93-4
----, oases of, 65, 98, 99, 101
----, thermograph of, 91, 92
----, winds of, 77
Mendeleeff, 39
Mercury, 114-18
Messier, lunar crater, 47, 48
Metabolism, 10, 11, 14, 15, 38
Millechau, 104
Milton, 51
Mira Ceti, 150
Molesworth, P. B., 49, 104
Moon, 43-56
----, "terminator" of, 51
Mont Blanc, 25, 74, 80
Mount Everest, 75, 80
Nature of Vision, 99
Nebulae, spectrum of, 38, 40
Nebulium, 40
Negative elements, 36
Neison, E., 48, 53
Neptune, 132, 141
Newcomb, S., 93, 109
Nicholson, J. W., 40
Nickel, 33
Nilosyrtis, "canal" on Mars, 89
Nitrogen, 11, 37, 38, 39
Observatory, Chicago, 44
----, Harvard College, 127
----, Lick, 122
----, Paris, 44
Occultation, 52, 53
Organic Life, definition of, 15
Organism, living, 6-19
Organo-genetic elements, 12, 38, 39
Osmosis, 15
Oxygen, 11, 36, 37, 38, 41
Periodic Law, Mendeleeff's, 39
Phillips, T. E. R., 104
Phosphorus, 12
Photosphere, 28, 33, 36
Pickering, W. H., 47, 48, 53, 109
Pithecanthropus, 155
Planetary statistics, table of, 72, 73, 135
Platinum, 36
"Plurality of Worlds," 2
Pollock, Master, 109
Potassium, 12
Poynting, J. H., 86, 87, 89, 115
Proctor, R. A., 34, 77
Prominences, 29, 30, 37
Protofluorine, 40
Protonilus, "canal" on Mars, 89
Protoplasm, 11, 12, 13, 15, 38, 40, 154
Pyramid, Great, 45
Refraction, anomalous, 28
Reversing layer, 36
"Rice-grains," of Sun's surface, 28, 29
Ring Nebula in Lyra, 40
Rosse, Lord, 55
Ruskin, J., 19
Saturn, 132
----, Rings of, 138
Schiaparelli, G. V., 61, 62, 63, 64, 66, 97, 99, 107, 108, 116, 117
Schooling, T. Holt, 83
"Scientia," 66
"Semi-suns," 131, 132
Serviss, Garrett P., 17
Singapore, climate of, 87, 88
Sinus Sabaeus, marking on Mars, 97, 99
Sirius, 37
Sodium, 33, 36
"Solar Constant," 26
Spectroscopic binaries, 144, 145
Spectrum, 53
----, heat, 55
"Spurious" disc, 103
Stars, double, 35
----, multiple, 35
----, red, 38
----, spectra of, 34, 38, 39
Stefan's Law, 85
Stoney, G. Johnstone, 34
"Streaming," 15
Sulphur, 11, 38
Sun, 20-32
Sunspots, 29, 30, 31, 38
----, spectra of, 37
Swift, Dean, 82, 156
Table Mountain, 54
Thermograph of Mars, 91, 92
Titanium, 36, 37, 38
Tornadoes, 31, 137
"Twinkler," 114
Tycho, lunar crater, 46
Uranus, 132, 140
Venus, 57, 111-18
Verworn, Max, 7
Very, F. W., 55
Vesper, 111
"Victoria," hypothetical planet, 83
Wallace, A. R., 4
"War of the Worlds," 104, 156
Waste, 151, 152
Water, indispensable factor, 15, 41
Wells, H. G., 104, 156
Whewell, 4
Williams, A. Stanley, 104
Wolf, Max, 40
Young, C. A., 26, 33
WILLIAM BRENDON AND SON, LTD.
PRINTERS, PLYMOUTH
Footnotes:
[1] _Chemical Phenomena in Life_, pp. 62-3, by Dr. Frederick Czapek
(Harper's Library of Living Thought). The reader is strongly recommended
to study this work in the present connection.
[2] _Wonders of Life_, by Ernst Haeckel, Professor at Jena University, p.
130.
[3] _Wonders of Life_, pp. 127-8.
[4] _Chemical Phenomena in Life_, p. 58.
[5] _Ibid._, p. 22.
[6] _Other Worlds_, by Garrett P. Serviss, pp. 63-4.
[7] _Modern Painters_, by John Ruskin.
[8] If this experiment could be carried out, it would be necessary to use
a spring balance. If the object were weighed in a pair of scales or by a
steelyard, the counterbalancing weights would be likewise affected in the
same proportion, so that the equilibrium would be undisturbed.
[9] The movements of not a few double stars point to perturbations caused
by the attraction of unseen bodies. There are also a number of instances
known of "Eclipse" or "Algol-type" variable stars, in which the presence
of a dark companion is indicated by the diminution of the light of the
star at regular intervals.
[10] _Proc. R. Soc._, LXXX, 50, 1907.
[11] _Nature_, LXXX, 158 (April 8th, 1909).
[12] "Periodic Changes upon the Moon," _Memoirs_, British Astronomical
Association, Vol. XIII, p. 88.
[13] _The Moon_, by Philip Fauth, p. 156.
[14] _Radiation in the Solar System: Its Effects on Temperature, and its
Pressure on Small Bodies_, by Dr. J. H. Poynting (_Phil. Trans. of the
Royal Society_, Vol. 202 A).
[15] _Publ. of the Astron. Soc. of the Pacific_, Vol. II, pp. 286-8.
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Transcriber's Notes:
Passages in italics are indicated by _italics_.
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The original text includes symbols which are represented by [Symbol] in
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End of Project Gutenberg's Are the Planets Inhabited?, by E. Walter Maunder