OUTLINES OF THE
EARTH'S HISTORY
A POPULAR STUDY
IN PHYSIOGRAPHY
BY
NATHANIEL SOUTHGATE SHALER
PROFESSOR OF GEOLOGY IN HARVARD UNIVERSITY
DEAN OF LAWRENCE SCIENTIFIC SCHOOL
ILLUSTRATED WITH INDEX
NEW YORK AND LONDON
D. APPLETON AND COMPANY
1898, 1910
PREFACE.
The object of this book is to provide the beginner in the study of the
earth's history with a general account of those actions which can be
readily understood and which will afford him clear understandings as
to the nature of the processes which have made this and other
celestial spheres. It has been the writer's purpose to select those
series of facts which serve to show the continuous operations of
energy, so that the reader might be helped to a truer conception of
the nature of this sphere than he can obtain from ordinary text-books.
In the usual method of presenting the elements of the earth's history
the facts are set forth in a manner which leads the student to
conceive that history as in a way completed. The natural prepossession
to the effect that the visible universe represents something done,
rather than something endlessly doing, is thus re-enforced, with the
result that one may fail to gain the largest and most educative
impression which physical science can afford him in the sense of the
swift and unending procession of events.
It is well known to all who are acquainted with the history of geology
that the static conception of the earth - the idea that its existing
condition is the finished product of forces no longer in action - led
to prejudices which have long retarded, and indeed still retard, the
progress of that science. This fact indicates that at the outset of a
student's work in this field he should be guarded against such
misconceptions. The only way to attain the end is by bringing to the
understanding of the beginner a clear idea of successions of events
which are caused by the forces operating in and on this sphere. Of all
the chapters of this great story, that which relates to the history of
the work done by the heat of the sun is the most interesting and
awakening. Therefore an effort has been made to present the great
successive steps by which the solar energy acts in the processes of
the air and the waters.
The interest of the beginner in geology is sure to be aroused when he
comes to see how very far the history of the earth has influenced the
fate of men. Therefore the aim has been, where possible, to show the
ways in which geological processes and results are related to
ourselves; how, in a word, this earth has been the well-appointed
nursery of our kind.
All those who are engaged in teaching elementary science learn the
need of limiting the story they have to tell to those truths which can
be easily understood by beginners. It is sometimes best, as in stating
such difficult matters as those concerning the tides, to give
explanations which are far from complete, and which, as to their mode
of presentation, would be open to criticism were it not for the fact
that any more elaborate statements would most likely be
incomprehensible to the novice, thus defeating the teacher's aim.
It will be observed that no account is here given of the geological
ages or of the successions of organic life. Chapters on these subjects
were prepared, but were omitted for the reason that they made the
story too long, and also because they carried the reader into a field
of much greater difficulty than that which is found in the physical
history of the earth.
N.S.S.
_March, 1898._
CONTENTS.
CHAPTER PAGE
I. - INTRODUCTION TO THE STUDY OF NATURE 1
II. - WAYS AND MEANS OF STUDYING NATURE 9
III. - THE STELLAR REALM 31
IV. - THE EARTH 81
V. - THE ATMOSPHERE 97
VI. - GLACIERS 207
VII. - THE WORK OF UNDERGROUND WATER 250
VIII. - THE SOIL 313
IX. - THE ROCKS AND THEIR ORDER 349
LIST OF FULL-PAGE ILLUSTRATIONS.
FACING PAGE
Dunes at Ipswich Light, Massachusetts _Frontispiece_
Seal Rocks near San Francisco, California 33
Lava stream, in Hawaiian Islands, flowing into the sea 72
Waterfall near Gadsden, Alabama 90
South shore, Martha's Vineyard, Massachusetts 121
Pocket Creek, Cape Ann, Massachusetts 163
Muir Glacier, Alaska 207
Front of Muir Glacier 240
Mount Ætna, seen from near Catania 201
Mountain gorge, Himalayas, India 330
OUTLINES OF THE EARTH'S HISTORY.
CHAPTER I.
AN INTRODUCTION TO THE STUDY OF NATURE.
The object of this book is to give the student who is about to enter
on the study of natural science some general idea as to the conditions
of the natural realm. As this field of inquiry is vast, it will be
possible only to give the merest outline of its subject-matter, noting
those features alone which are of surpassing interest, which are
demanded for a large understanding of man's place in this world, or
which pertain to his duties in life.
In entering on any field of inquiry, it is most desirable that the
student should obtain some idea as to the ways in which men have been
led to the knowledge which they possess concerning the world about
them. Therefore it will be well briefly to sketch the steps by which
natural science has come to be what it is. By so doing we shall
perceive how much we owe to the students of other generations; and by
noting the difficulties which they encountered, and how they avoided
them, we shall more easily find our own way to knowledge.
The primitive savages, who were the ancestors of all men, however
civilized they may be, were students of Nature. The remnants of these
lowly people who were left in different parts of the world show us
that man was not long in existence before he began to devise some
explanation concerning the course of events in the outer world.
Seeing the sun rise and set, the changes of the moon, the alternation
of the seasons, the incessant movement of the streams and sea, and the
other more or less orderly successions of events, our primitive
forefathers were driven to invent some explanation of them. This,
independently, and in many different times and places, they did in a
simple and natural way by supposing that the world was controlled by a
host of intelligent beings, each of which had some part in ordering
material things. Sometimes these invisible powers were believed to be
the spirits of great chieftains, who were active when on earth, and
who after death continued to exercise their power in the larger realms
of Nature. Again, and perhaps more commonly, these movements of Nature
were supposed to be due to the action of great though invisible
beasts, much like those which the savage found about him. Thus among
our North American Indians the winds are explained by the supposition
that the air is fanned by the wings of a great unseen bird, whose duty
it is to set the atmosphere into motion. That no one has ever seen the
bird doing the work, or that the task is too great for any conceivable
bird, is to the simple, uncultivated man no objection to this view. It
is long, indeed, before education brings men to the point where they
can criticise their first explanations of Nature.
As men in their advance come to see how much nobler are their own
natures than those of the lower animals, they gradually put aside the
explanation of events by the actions of beasts, and account for the
order of the world by the supposition that each and every important
detail is controlled by some immortal creature essentially like a man,
though much more powerful than those of their own kind. This stage of
understanding is perhaps best shown by the mythology of the Greeks,
where there was a great god over all, very powerful but not
omnipotent; and beneath him, in endless successions of command,
subordinate powers, each with a less range of duties and capacities
than those of higher estate, until at the bottom of the system there
were minor deities and demigods charged with the management of the
trees, the flowers, and the springs - creatures differing little from
man, except that they were immortal, and generally invisible, though
they, like all the other deities, might at their will display
themselves to the human beings over whom they watched, and whose path
in life they guided.
Among only one people do we find that the process of advance led
beyond this early and simple method of accounting for the processes of
Nature, bringing men to an understanding such as we now possess. This
great task was accomplished by the Greeks alone. About twenty-five
hundred years ago the philosophers of Greece began to perceive that
the early notion as to the guidance of the world by creatures
essentially like men could not be accepted, and must be replaced by
some other view which would more effectively account for the facts.
This end they attained by steps which can not well be related here,
but which led them to suppose separate powers behind each of the
natural series - powers having no relation to the qualities of mankind,
but ever acting to a definite end. Thus Plato, who represents most
clearly this advance in the interpretation of facts, imagined that
each particular kind of plant or animal had its shape inevitably
determined by something which he termed an idea, a shape-giving power
which existed before the object was created, and which would remain
after it had been destroyed, ever ready again to bring matter to the
particular form. From this stage of understanding it was but a short
step to the modern view of natural law. This last important advance
was made by the great philosopher Aristotle, who, though he died about
twenty-two hundred years ago, deserves to be accounted the first and
in many ways the greatest of the ancient men of science who were
informed with the modern spirit.
With Aristotle, as with all his intellectual successors, the
operations of Nature were conceived as to be accounted for by the
action of forces which we commonly designate as natural laws, of which
perhaps the most familiar and universal is that of gravitation, which
impels all bodies to move toward each other with a degree of intensity
which is measured by their weight and the distance by which they are
separated.
For many centuries students used the term law in somewhat the same way
as the more philosophical believers in polytheism spoke of their gods,
or as Plato of the ideas which he conceived to control Nature. We see
by this instance how hard it is to get rid of old ways of thinking.
Even when the new have been adopted we very often find that something
of the ancient and discarded notions cling in our phrases. The more
advanced of our modern philosophers are clear in their mind that all
we know as to the order of Nature is that, given certain conditions,
certain consequences inevitably follow.
Although the limitations which modern men of science perceive to be
put upon their labours may seem at first sight calculated to confine
our understanding within a narrow field of things which can be seen,
or in some way distinctly proved to exist, the effect of this
limitation has been to make science what it is - a realm of things
known as distinct from things which may be imagined. All the
difference between ancient science and modern consists in the fact
that in modern science inquirers demand a businesslike method in the
interpretation of Nature. Among the Greeks the philosopher who taught
explanations of any feature in the material world which interested him
was content if he could imagine some way which would account for the
facts. It is the modern custom now to term the supposition of an
explanation a _working hypothesis_, and only to give it the name of
theory after a very careful search has shown that all the facts which
can be gathered are in accordance with the view. Thus when Newton made
his great suggestion concerning the law of gravitation, which was to
the effect that all bodies attracted each other in proportion to
their masses, and inversely as the square of their distance from each
other, he did not rest content, as the old Greeks would have done,
with the probable truth of the explanation, but carefully explored the
movements of the planets and satellites of the solar system to see if
the facts accorded with the hypothesis. Even the perfect
correspondence which he found did not entirely content inquirers, and
in this century very important experiments have been made which have
served to show that a ball suspended in front of a precipice will be
attracted toward the steep, and that even a mass of lead some tons in
weight will attract toward itself a small body suspended in the manner
of a pendulum.
It is this incessant revision of the facts, in order to see if they
accord with the assumed rule or law, which has given modern science
the sound footing that it lacked in earlier days, and which has
permitted our learning to go on step by step in a safe way up the
heights to which it has climbed. All explanations of Nature begin with
the work of the imagination. In common phrase, they all are guesses
which have at first but little value, and only attain importance in
proportion as they are verified by long-continued criticism, which has
for its object to see whether the facts accord with the theory. It is
in this effort to secure proof that modern science has gathered the
enormous store of well-ascertained facts which constitutes its true
wealth, and which distinguishes it from the earlier imaginative and to
a great extent unproved views.
In the original state of learning, natural science was confounded with
political and social tradition, with the precepts of duty which
constitute the law of the people, as well as with their religion, the
whole being in the possession of the priests or wise men. So long as
natural action was supposed to be in the immediate control of numerous
gods and demigods, so long, in a word, as the explanation of Nature
was what we term polytheistic, this association of science with other
forms of learning was not only natural but inevitable. Gradually,
however, as the conception of natural law replaced the earlier idea as
to the intervention of a spirit, science departed from other forms of
lore and came to possess a field to itself. At first it was one body
of learning. The naturalists of Aristotle's time, and from his day
down to near our own, generally concerned themselves with the whole
field of Nature. For a time it was possible for any one able and
laborious man to know all which had been ascertained concerning
astronomy, chemistry, geology, as well as the facts relating to living
beings. The more, however, as observation accumulated, and the store
of facts increased, it became difficult for any one man to know the
whole. Hence it has come about that in our own time natural learning
is divided into many distinct provinces, each of which demands a
lifetime of labour from those who would know what has already been
done in the field, and what it is now important to do in the way of
new inquiries.
The large divisions which naturalists have usually made of their tasks
rest in the main on the natural partitions which we may readily
observe in the phenomenal world. First of all comes astronomy,
including the phenomena exhibited in the heavens, beyond the limits of
the earth's atmosphere. Second, geology, which takes account of all
those actions which in process of time have been developed in our own
sphere. Third, physics, which is concerned with the laws of energy, or
those conditions which affect the motion of bodies, and the changes
which are impressed upon them by the different natural forces. Fourth,
chemistry, which seeks to interpret the principles which determine the
combination of atoms and the molecules which are built of them under
the influence of the chemical affinities. Fifth, biology, or the laws
of life, a study which pertains to the forms and structures of animals
and plants, and their wonderful successions in the history of the
world. Sixth, mathematics, or the science of space and number, that
deals with the principles which underlie the order of Nature as
expressed at once in the human understanding and in the material
universe. By its use men were made able to calculate, as in
arithmetic, the problems which concern their ordinary business, as
well as to compute the movements of the celestial bodies, and a host
of actions which take place on the earth that would be inexplicable
except by the aid of this science. Last of all among the primary
sciences we may name that of psychology, which takes account of mental
operations among man and his lower kindred, the animals.
In addition to the seven sciences above mentioned, which rest in a
great measure on the natural divisions of phenomena, there are many,
indeed, indefinitely numerous, subdivisions which have been made to
suit the convenience of students. Thus astronomy is often separated
into physical and mathematical divisions, which take account either of
the physical phenomena exhibited by the heavenly bodies or of their
motions. In geology there are half a dozen divisions relating to
particular branches of that subject. In the realm of organic life, in
chemistry, and in physics there are many parts of these sciences which
have received particular names.
It must not be supposed that these sciences have the independence of
each other which their separate names would imply. In fact, the
student of each, however, far he may succeed in separating his field
from that of the other naturalists, as we may fitly term all students
of Nature, is compelled from time to time to call in the aid of his
brethren who cultivate other branches of learning. The modern
astronomer needs to know much of chemistry, or else he can not
understand many of his observations on the sun. The geologists have to
share their work with the student of animal and vegetable life, with
the physicists; they must, moreover, know something of the celestial
spheres in order to interpret the history of the earth. In fact, day
by day, with the advance of learning, we come more clearly to
perceive that all the processes of Nature are in a way related to each
other, and that in proportion as we understand any part of the great
mechanism, we are forced in a manner to comprehend the whole. In other
words, we are coming to understand that these divisions of the field
of science depend upon the limitations of our knowledge, and not upon
the order of Nature itself. For the purposes of education it is
important that every one should know something of the great truths
which each science has disclosed. No mortal man can compass the whole
realm of this knowledge, but every one can gain some idea of the
larger truths which may help him to understand the beauty and grandeur
of the sphere in which he dwells, which will enable him the better to
meet the ordinary duties of life, that in almost all cases are related
to the facts of the world about us. It has been of late the custom to
term this body of general knowledge which takes account of the more
evident facts and important series of terrestrial actions
physiography, or, as the term implies, a description of Nature, with
the understanding that the knowledge chosen for the account is that
which most intimately concerns the student who seeks information that
is at once general and important. Therefore, in this book the effort
is made first to give an account as to the ways and means which have
led to our understanding of scientific problems, the methods by which
each person may make himself an inquirer, and the outline of the
knowledge that has been gathered since men first began to observe and
criticise the revelations the universe may afford them.
CHAPTER II.
WAYS AND MEANS OF STUDYING NATURE.
It is desirable that the student of Nature keep well in mind the means
whereby he is able to perceive what goes on in the world about him. He
should understand something as to the nature of his senses, and the
extent to which these capacities enable him to discern the operations
of Nature. Man, in common with his lower kindred, is, by the mechanism
of the body, provided with five somewhat different ways by which he
may learn something of the things about him. The simplest of these
capacities is that of touch, a faculty that is common to the general
surface of the body, and which informs us when the surface is affected
by contact with some external object. It also enables us to discern
differences of temperature. Next is the sense of taste, which is
limited to the mouth and the parts about it. This sense is in a way
related to that of touch, for the reason that it depends on the
contact of our body with material things. Third is the sense of smell,
so closely related to that of taste that it is difficult to draw the
line between the two. Yet through the apparatus of the nose we can
perceive the microscopically small parts of matter borne to us through
the air, which could not be appreciated by the nerves of the mouth.
Fourth in order of scope comes the hearing, which gives us an account
of those waves of matter that we understand as sound. This power is
much more far ranging than those before noted; in some cases, as in
that of the volcanic explosions from the island of Krakatoa, in the
eruption of 1883, the convulsions were audible at the distance of
more than a thousand miles away. The greater cannon of modern days may
be heard at the distance of more than a hundred miles, so that while
the sense of touch, taste, and smell demand contact with the bodies
which we appreciate, hearing gives us information concerning objects
at a considerable distance. Last and highest of the senses, vastly the
most important in all that relates to our understanding of Nature, is
sight, or the capacity which enables us to appreciate the movement of
those very small waves of ether which constitute light. The eminent
peculiarity of sight is that it may give us information concerning
things which are inconceivably far away; it enables us to discern the
light of suns probably millions of times as remote from us as is the
centre of our own solar system.
Although much of the pleasure which the world affords us comes through
the other senses, the basis of almost all our accurate knowledge is
reported by sight. It is true that what we have observed with our eyes
may be set forth in words, and thus find its way to the understanding
through the ears; also that in many instances the sense of touch
conveys information which extends our perceptions in many important
ways; but science rests practically on sight, and on the insight that
comes from the training of the mind which the eyes make possible.
The early inquirers had no resources except those their bodies
afforded; but man is a tool-making creature, and in very early days he
began to invent instruments which helped him in inquiry. The earliest
deliberate study was of the stars. Science began with astronomy, and
the first instruments which men contrived for the purpose of
investigation were astronomical. In the beginning of this search the
stars were studied in order to measure the length of the year, and
also for the reason that they were supposed in some way to control the
fate of men. So far as we know, the first pieces of apparatus for this
purpose were invented in Egypt, perhaps about four thousand years
before the Christian era. These instruments were of a simple nature,
for the magnifying glass was not yet contrived, and so the telescope
was impossible. They consisted of arrangements of straight edges and
divided circles, so that the observers, by sighting along the
instruments, could in a rough way determine the changes in distance
between certain stars, or the height of the sun above the horizon at
the various seasons of the year. It is likely that each of the great
pyramids of Egypt was at first used as an observatory, where the
priests, who had some knowledge of astronomy, found a station for the
apparatus by which they made the observations that served as a basis
for casting the horoscope of the king.
In the progress of science and of the mechanical invention attending
its growth, a great number of inventions have been contrived which
vastly increase our vision and add inconceivably to the precision it
may attain. In fact, something like as much skill and labour has been
given to the development of those inventions which add to our learning
as to those which serve an immediate economic end. By far the greatest
of these scientific inventions are those which depend upon the lens.
By combining shaped bits of glass so as to control the direction in
which the light waves move through them, naturalists have been able to
create the telescope, which in effect may bring distant objects some
thousand times nearer to view than they are to the naked eye; and the
microscope, which so enlarges minute objects as to make them visible,
as they were not before. The result has been enormously to increase
our power of vision when applied to distant or to small objects. In
fact, for purposes of learning, it is safe to say that those tools
have altogether changed man's relation to the visible universe. The
naked eye can see at best in the part of the heavens visible from any
one point not more than thirty thousand stars. With the telescope
somewhere near a hundred million are brought within the limits of
vision. Without the help of the microscope an object a thousandth of
an inch in diameter appears as a mere point, the existence of which we
can determine only under favourable circumstances. With that
instrument the object may reveal an extended and complicated structure
which it may require a vast labour for the observer fully to explore.
Next in importance to the aid of vision above noted come the
scientific tools which are used in weighing and measuring. These
balances and gauges have attained such precision that intervals so
small as to be quite invisible, and weights as slight as a
ten-thousandth of a grain, can be accurately measured. From these
instruments have come all those precise examinations on which the
accuracy of modern science intimately depends. All these instruments
of precision are the inventions of modern days. The simplest
telescopes were made only about two hundred and fifty years ago, and
the earlier compound microscopes at a yet later date. Accurate
balances and other forms of gauges of space, as well as good means of
dividing time, such as our accurate astronomical clocks and
chronometers, are only about a century old. The instruments have made
science accurate, and have immensely extended its powers in nearly all
the fields of inquiry.
Although the most striking modern discoveries are in the field which
was opened to us by the lens in its manifold applications, it is in
the chemist's laboratory that we find that branch of science, long
cultivated, but rapidly advanced only within the last two centuries,
which has done the most for the needs of man. The ancients guessed
that the substances which make up the visible world were more
complicated in their organization than they appear to our vision. They
even suggested the great truth that matter of all kinds is made up of
inconceivably small indivisible bits which they and we term atoms. It
is likely that in the classic days of Greece men began to make simple
experiments of a chemical nature. A century or two after the time of
Mohammed, the Arabians of his faith, a people who had acquired Greek
science from the libraries which their conquests gave them, conducted
extensive experiments, and named a good many familiar chemical
products, such as alcohol, which still bears its Arabic name.
These chemical studies were continued in Europe by the alchemists, a
name also of Arabic origin, a set of inquirers who were to a great
extent drawn away from scientific studies by vain though unending
efforts to change the baser metals into gold and silver, as well as to
find a compound which would make men immortal in the body. By the
invention of the accurate balance, and by patient weighing of the
matters which they submitted to experiment, by the invention of
hypotheses or guesses at truth, which were carefully tested by
experiment, the majestic science of modern chemistry has come forth
from the confused and mystical studies of the alchemists. We have
learned to know that there are seventy or more primitive or apparently
unchangeable elements which make up the mass of this world, and
probably constitute all the celestial spheres, and that these elements
in the form of their separate atoms may group themselves in almost
inconceivably varied combinations. In the inanimate realm these
associations, composed of the atoms of the different substances,
forming what are termed molecules, are generally composed of but few
units. Thus carbonic-acid gas, as it is commonly called, is made up of
an aggregation of molecules, each composed of one atom of carbon and
two of oxygen; water, of two atoms of hydrogen and one of oxygen;
ordinary iron oxide, of two atoms of iron and three of oxygen. In the
realm of organic life, however, these combinations become vastly more
complicated, and with each of them the properties of the substance
thus produced differ from all others. A distinguished chemist has
estimated that in one group of chemical compounds, that of carbon, it
would be possible to make such an array of substances that it would
require a library of many thousand ordinary volumes to contain their
names alone.
It is characteristic of chemical science that it takes account of
actions which are almost entirely invisible. No contrivances have been
or are likely to be invented which will show the observer what takes
place when the atoms of any substance depart from their previous
combination and enter on new arrangements. We only know that under
certain conditions the old atomic associations break up, and new ones
are formed. But though the processes are hidden, the results are
manifest in the changes which are brought about upon the masses of
material which are subjected to the altering conditions. Gradually the
chemists of our day are learning to build up in their laboratories
more and more complicated compounds; already they have succeeded in
producing many of the materials which of old could only be obtained by
extracting them from plants. Thus a number of the perfumes of flowers,
and many of the dye-stuffs which a century ago were extracted from
vegetables, and were then supposed to be only obtainable in that way,
are now readily manufactured. In time it seems likely that important
articles of food, for which we now depend upon the seeds of plants,
may be directly built up from the mineral kingdom. Thus the result of
chemical inquiry has been not only to show us much of the vast realm
of actions which go on in the earth, but to give us control of many of
these movements so that we may turn them to the needs of man.
Animals and plants were at an early day very naturally the subjects of
inquiry. The ancients perceived that there were differences of kind
among these creatures, and even in Aristotle's time the sciences of
zoölogy and botany had attained the point where there were
considerable treatises on those subjects. It was not, however, until a
little more than a century ago that men began accurately to describe
and classify these species of the organic world. Since the time of
Linnæus the growth of our knowledge has gone forward with amazing
swiftness. Within a century we have come to know perhaps a hundred
times as much concerning these creatures as was learned in all the
earlier ages. This knowledge is divisible into two main branches: in
one the inquirers have taken account of the different species, genera,
families, orders, and classes of living forms with such effect that
they have shown the existence at the present time of many hundred
thousand distinct species, the vast assemblage being arranged in a
classification which shows something as to the relationship which the
forms bear to each other, and furthermore that the kinds now living
have not been long in existence, but that at each stage in the history
of the earth another assemblage of species peopled the waters and the
lands.
At first naturalists concerned themselves only with the external forms
of living creatures; but they soon came to perceive that the way in
which these organisms worked, their physiology, in a word, afforded
matters for extended inquiry. These researches have developed the
science of physiology, or the laws of bodily action, on many accounts
the most modern and extensive of our new acquisitions of natural
learning. Through these studies we have come to know something of the
laws or principles by which life is handed on from generation to
generation, and by which the gradations of structure have been
advanced from the simple creatures which appear like bits of animated
jelly to the body and mind of man.
The greatest contribution which modern naturalists have made to
knowledge concerns the origin of organic species. The students of a
century ago believed that all these different kinds had been suddenly
created either through natural law or by the immediate will of God. We
now know that from the beginning of organic life in the remote past to
the present day one kind of animal or plant has been in a natural and
essentially gradual way converted into the species which was to be its
successor, so that all the vast and complicated assemblage of kinds
which now exists has been derived by a process of change from the
forms which in earlier ages dwelt upon this planet. The exact manner
in which these alterations were produced is not yet determined, but in
large part it has evidently been brought about by the method indicated
by Mr. Darwin, through the survival of the fittest individuals in the
struggle for existence.
Until men came to have a clear conception as to the spherical form of
the earth, it was impossible for them to begin any intelligent
inquiries concerning its structure or history. The Greeks knew the
earth to be a sphere, but this knowledge was lost among the early
Christian people, and it was not until about four hundred years ago
that men again came to see that they dwelt upon a globe. On the basis
of this understanding the science of geology, which had in a way been
founded by the Greeks, was revived. As this science depends upon the
knowledge which we have gained of astronomy, physics, chemistry, and
biology, all of which branches of learning have to be used in
explaining the history of the earth, the advance which has been made
has been relatively slow. Geology as a whole is the least perfectly
organized of all the divisions of learning. A special difficulty
peculiar to this science has also served to hinder its development.
All the other branches of learning deal mainly, if not altogether,
with the conditions of Nature as they now exist. In this alone is it
necessary at every step to take account of actions which have been
performed in the remote past.
It is an easy matter for the students of to-day to imagine that the
earth has long endured; but to our forefathers, who were educated in
the view that it had been brought from nothingness into existence
about seven thousand years ago, it was most difficult and for a time
impossible to believe in its real antiquity. Endeavouring, as they
naturally did, to account for all the wonderful revolutions, the
history of which is written in the pages of the great stone book, the
early geologists supposed this planet to have been the seat of
frequent and violent changes, each of which revolutionized its shape
and destroyed its living tenants. It was only very gradually that
they became convinced that a hundred million years or more have
elapsed since the dawn of life on the earth, and that in this vast
period the march of events has been steadfast, the changes taking
place at about the same rate in which they are now going on. As yet
this conception as to the history of our sphere has not become the
general property of the people, but the fact of it is recognised by
all those who have attentively studied the matter. It is now as well
ascertained as any of the other truths which science has disclosed to
us.
It is instructive to note the historic outlines of scientific
development. The most conspicuous truth which this history discloses
is that all science has had its origin and almost all its development
among the peoples belonging to the Aryan race. This body of folk
appears to have taken on its race characteristics, acquired its
original language, its modes of action, and the foundations of its
religion in that part of northern Europe which is about the Baltic
Sea. Thence the body of this people appear to have wandered toward
central Asia, where after ages of pastoral life in the high table
lands and mountains of their country it sent forth branches to India,
Asia Minor and Greece, to Persia, and to western Europe. It seems ever
to have been a characteristic of these Aryan peoples that they had an
extreme love for Nature; moreover, they clearly perceived the need of
accounting for the things that happened in the world about them. In
general they inclined to what is called the pantheistic explanation of
the universe. They believed a supreme God in many different forms to
be embodied in all the things they saw. Even their own minds and
bodies they conceived as manifestations of this supreme power. Among
the Aryans who came to dwell in Europe and along the eastern
Mediterranean this method of explaining Nature was in time changed to
one in which humanlike gods were supposed to control the visible and
invisible worlds. In that marvellous centre of culture which was
developed among the Greeks this conception of humanlike deities was in
time replaced by that of natural law, and in their best days the
Greeks were men of science essentially like those of to-day, except
that they had not learned by experience how important it was to
criticise their theories by patiently comparing them with the facts