xt7xks6j1r3m https://exploreuk.uky.edu/dips/xt7xks6j1r3m/data/mets.xml Shaler, Nathaniel Southgate, 1841-1906. 1891  books b92-258-31813919 English Ginn, : Boston : Contact the Special Collections Research Center for information regarding rights and use of this collection. Physical geography North America. Geology North America. Story of our continent  : a reader in the geography and geology of North America, for the use of schools / by N.S. Shaler. text Story of our continent  : a reader in the geography and geology of North America, for the use of schools / by N.S. Shaler. 1891 2002 true xt7xks6j1r3m section xt7xks6j1r3m 



A Reader

ilt the Geograply and Geology
of Nortb America



      N. S. SHALER





  By N. S. SHALER.



Irbt gtbentum Breas
G IN N &. CMN.PA N Y -'RO-



  THOSE who read this book will at once perceive that
both in the subject-matter and arrangement it departs
widely from the ordinary text-books which give an
account of North America.  It should be understood
that the end which the writer sought to attain is not
that which may be secured by the ordinary school
geographies.  Such works undertake to afford the
student a large body of detailed information concerning
the existing state of the country, and with little or no
reference to the steps by which the land came to its
present estate. The aim of this work has been to pre-
sent only those features which can be shown in their
relation to the geological development of the continent.
  The expectation of the author has been that this work
will be used as a reader along with some geography
which treats in a thorough way the facts of a political
and economic nature, such as these text-books ordi-
narily present.  Used in this manner, it will naturally
lead the student to perceive how the present state of
the country is due to the processes which have gone
on in the remote past, and in this way to attain to
some of the most enlarging conceptions which the
geological history of the earth unfolds.

 This page in the original text is blank.



                      CHAPTER I.


                     CllALrTER IL.



                     CHAPTER III.


                     CHAPTER IV.


                     CHAPTER V.


                     CHAPTER VI.



                     CHAPTER VII.



 This page in the original text is blank.



                    CHAPTER      I.


Method of study. Cause and effect of climate. Influence of geographic
  conditions on animals andl plants; on the life of man. Character of the
  soil. Origin of its fertility. General influence of geologic and geo-
  graphic conditions on mankind.

  IN beginning the study of the geography of North
America, it is well for us to form a clear idea as to the
object which we should have in view in this task. With
a distinct aim before us, it is easily seen that labor
may be spared in the effort. It is a large task to form
even the most general idea of the history and condi-
tions of a great area of the earth's surface. The amount
of knowledge concerning any one of the continents is
so vast that to secure a general view of its conditions
we have to neglect the greater part of the details con-
cerning its growth and structure. If our plan be clearly
marked, we can more easily put the unnecessary learn-
ing aside.
  The most of our school geographies seek to present
to the student a picture of the existing conditions on
the earth's surface, to show him the shape of the
lands, the boundaries of states, the character of the im-



portant natural features, the conditions of commerce; in
other words, to give him a picture of the earth, or a par-
ticular part of it, as it now is. In this little volume we
are to consider something more than is commonly pre-
sented in such work, the intention being to show the
student in a general way how the continent of North
America has come by its shape, through what steps it
has become a land, how the stages of its growth have
affected its climate, and thus have influenced the charac-
te-r of living things which have found a place upon its
lands, and finally in what manner the past history of the
continent, by determining the store of mineral materials
under the earth, the shape of its surface, the nature of
its soil and climate, measures its fitness for the uses of
man ; in a word, how the history of its people has been
influenced by geographic conditions, and thus depends
on the laws which have controlled the development of a
continental mass.
  In the effort to see how the geography of any country
has influenced the life of the animals and plants which
have found a place upon it, it is well for the student to
begin his task by noticing a number of familiar facts,
so familiar, indeed, that they readily escape attention,
which may serve to illustrate the effect of surrounding
conditions on the sensitive living creatures. It is easy
to see that all the living tenants of the lands and waters
are readily and largely influenced by the conditions of
the nature about them.
  Any one who has made himself moderately familiar
with the round of the seasons has observed the profound
effect arising from changes of climate.  In the regions
north and south of the tropics each year brings periods
of winter and of summer; with the change in the




amount of heat the living beings pass from the sleep of
the winter season to the activity of summer time. In
the springtime, when the sun rises higher above the
horizon and sends more heat to the earth, we perceive
the effect of the alteration on the development of life.
The seeds are stimulated to growth, and most of the ani-
mals which have reposed in hidden places come forth
and enter on their busy lives. Every year thus affords a
beautiful lesson on the effects of simple changes in the
events of the outer world. As the sun ascends higher,
it brings with it a tropical climate, which marches over
the surface nearly to the boles; then as the sun returns
south in its annual course, the conditions of polar cold
sweep down towards the equator. The difference be-
tween the tropical belt of the world and the regions
beyond it lies in the fact that within the tropics it is al-
ways warm with something like the warmth of summer
in higher latitudes, while near the poles the temperature
is tropical for only a short time. If the summer heat
continued throughout the year in any high latitude,
palms and other plants which cannot withstand the cold
would develop over nearly all the earth's lands.
  After we have in mind the effect produced by the
alternate rising and sinking of the sun in high latitudes,
it is well next to note the effects on the district about
us caused by differences in the geographic character
of the land. In any country where there is a range
of heights of even a few feet, where there are streams
and hills however small, we may with a little study see
how the nature of the surface, by determining the
character of the soil, and the amount of water it con-
tains, affects the lives of the plants and animals. In
a lake or arm of the sea we note that in the deeper




water there arc no plants such as we have upon the
land ; the vegetable life is limited to certain soft forms
which are without leaves, or roots, or seeds of a
distinct kind. These aquatic plants live altogether be-
neath the surface of the waters, or at times tolerate
the air for a few hours at low tide. Close to the shore,
where the water is shallow, we may, if the water be
fresh, find certain higher plants, such as our lilies, and
rushes, which have distinct leaves, roots, and seed, and
can maintain themselves with their roots below the
surface of the water, but with their upper parts within
the air. Next the shore, if the ground happens to be
marshy, - that is, neither wet nor dry, - bushes and a
few kinds of trees may grow, forms which cannot inhabit
the water, and are equally incapable of living on the high
land. Passing yet further above the water to the lands
of a medium degree of wetness, yet other forms of lowly
plants or trees possess the land. On the arid hilltops
we find another assemblage of plants unlike any of
those which dwell on lower ground.
  Although it is not easy to see that the animal life is
limited in the same narrow way by geographic condi-
tions as is the vegetable world, closer inquiry shows us
that in fact most animals, because they depend for their
subsistence on particular kinds of plants, are also pro-
foundly affected by peculiarities of the soil. This is
particularly the case with insects, a group which con-
tains more kinds of creatures than all the rest of the
animal kingdom put together.   Most insects require
particular parts of plants for their food.  Even those
forms which live on other insects have to maintain
themselves where their prey is plentiful. The insects
of the swamp differ in a clear way from those of the




upland. Thus in the state of nature, in every country,
the living beings are distributed with reference to the
character of the soil, whence all land life springs. The
character of this soil depends upon the geography of
the country. The underlying rocks, the rivers, lakes,
hills, and mountains, mainly determine the nature of
that soil, whether it be wet or dry, of clay, sandy or
stony. All these features are fixed by the geological
history of the country: they can be accounted for only
where we know its past history, -how it came to have
its present form.
  Not only is the higher life of a land shaped by its
geographic conditions, but the life of man is influenced
even more than that of any other animal by the circum-
stances which surround him. If he be a farmer, the
character of the crops he cultivates will be determined
partly by the nature of the soil, and yet more by the
character of the climate, - the amount of heat which the
sun sends to him, or the share of rainfall which comes
to his fields.  He rears those crops which are made
possible by the heat, the rain, and the nature of the
earth on which they fall.  In the Southern states of
this country cotton is the leading product of the fields.
It is profitable to grow it there, for the reason that the
plant requires a very long summer to mature its bolls,
and during this summer there must be a considerable
fall of rain, and all the while a rather high temperature.
Moreover, cotton requires a sandy rather than a clayey
soil, and the ancient history of that part of the continent,
as we shall see hereafter, favored the construction of
soils of this nature. The farmers of the Northwestern
states find their profit in raising grain. That region is
the granary of the continent, - indeed, we may say of




Europe as well, - for the reason that the short, rather
dry summer affords a suitable climate for the develop-
ment of such crops, and the soil is generally of a clayey
nature, having this quality given it by the geological
conditions of the rocks made in the time when the con-
tinent was forming. Geographic conditions, those now
existing or those which have ceased to be, but have left
their marks on the character of the soil, make it im-
possible for cotton to be profitably reared in the North-
vest, or wheat in the Carolinas. Or, to take another
instance, the state of Fllorida is unfit for the tillage
either of grain or of cotton; the latter crop will grow
there, but the soil is not of a nature to make it profitable.
Florida is the field of fruit culture.  Its semi-tropical
climate favors the development of oranges, lemons,
pineapples, and many forms of fruit and vegetables.
The soil is generally so poor that these plants have to
be grown with the aid of artificial manures, and so that
portion of the country is by nature set aside for garden-
in-.  The character of the soil, combined with the
character of the climate of a country, serves to fix the
occupations of the people who win food from the earth.
Now the soil, simple as it seems to be at first sight, has
always a very wonderful history. So much depends upon
this history that we must ask the reader to turn his
attention for a moment to the nature and origin of this
film of loose material on the surface of the earth in
which the plants find root.
  All soils consist in the main of fine bits of rock, the
particles of clay and sand which have been worn from
the compact, firm-set under-rocks of the earth, by the
action of rain, frost, rivers, waves, and the roots of
plants, as well as by the decay which the atmosphere




brings to all rock material. If we take a pinch of soil
and spread it out thinly upon a sheet of white paper
and inspect it with a magnifying-,glass, we find that
the greater part of the material is commonly made tup
of tolerably coarse grains, large enough to be seen by
the naked eye or by a simple microscope. Mixed with
these hard bits there are very many fragments of de-
cayed roots, leaves, and stems, which are in part so
finely divided that they give the mass a dark color.
Sinking through the soil, the rain-water constantly takes
a little of the decayed rock into solution as salt dissolves
in water. This dissolved rock material is taken up by
the roots of plants, and affords the ashy matter of their
1o(ies, - material without which they could not grow.
On the proportion of lime, potash, phosphatic matter,
so(Ia, and various other materials which the decaying
rock affords to the soil-water, (lepen(ls the fertility of
the soil ; that is, its fitness to nourish crops, whether
those of wild nature or of the tilled fields. If the bits
which make the soil are largely composed of limestone,
which generally contains not only lime, but some phos-
phatic matter, soda, potash, and the other materials
required to make the bodies of plants, the soil will be
fertile. If, however, it be in the main made up of
quartzy bits of sand, the plants can obtain from the soil-
water but little nutriment, and therefore the fields will
be sterile, and the forests or the cultivated crops scanty.
  The proportion of fertilizing materials contained in
the soil depends upon the conditions which existed
when the rocks from which the soil is derived were
forming. Nearly all our rocks were formed on old sea-
floors. If the geography of those old sea-floors, that is
to say, the conditions of temperature and other circum-




stances, were such as to makc  plentiful life of shell-
fish or corals on the bottom, then the rocks formed from
the remains of these creatures will abound in materials
fit for plant growth. When this rock matter is sub-
jected to decay and accumulates in the soil, the plants
will flourish upon it. Each wheat plant will appropriate
the waste of these old creatures of the sea-floor, and
convert the chemical materials which they contributed
to the rock into good grain. Thus we readily see that
the character of our soils depends upon geographic con-
ditions in very remote time. A striking instance of this
effect may be found in the case of the very fertile lime-
stone lands which are found in the so-called blue-grass
district of Kentucky and Tennessee. These soils are of
extraordinary fertility and of such endurance to cultiva-
tion that they have been tilled in corn without manuring
for one hundred years or more. They owe their fertility
to the fact that the rock contains a large number of the
remains of animals somewhat akin to the shrimps.
These creatures had the habit of storing in their hard
parts a great deal of lime phosphate, which is the most
important ingredient in soils which are to feed grain.
The rocks beneath the blue-grass district are thin sheets
of limestone laid one above the other to the thickness
of a thousand feet or more; here and there there are
beds, generally only a few inches thick, mainly composed
of the remains of these little creatures, which are ex-
posed to the atmosphere. These beds decay to a fine
powder which works down through the hillsides, min-
gles with the soil, and so gives it its great fertility for
crops of grain and grass.
  The growth of ancient animals which built their re-
mains into rock was determined, as is the growth of




creatures of to-day, by geographic conditions. Other
circumstances of the earth's crust determined that in the
course of time these old sea-bottoms should be elevated
into dry land and exposed to the actions which make
soil. Thus we see that each stage in the earth's history
prepares the way for the later stages of its development.
Our life of to-day depends upon the conditions of re-
mote times.
  Although it is through the soil and climate that geo-
logical conditions most intimately affect the life of man,
there are very many ways in which the geography of
the past and present influence his career. Let us, for
example, note the influence of the sea on the occupations
of men. Wherever men's dwelling-places are along the
shore, they find a considerable share of their food in the
animals of the sea. They are thus tempted to seafar-
ing, to the construction of boats, and come to have the
peculiar needs which such life imposes on man. Yet
later in their development they find a profit in the trade
which the fields of the sea lay wide open to those who
(dwell upon its borders. Thus, while inland people are
limited to the district just about them for their field of
action, the folk next to the shore have a vastly wider
range of employment. The peculiarities of their life
depend upon the way in which the lands have grown
to their present shape.
  The fitness of the shore for the uses of the mariner
varies greatly. Where the coast is very sandy and
there are no large rivers passing across the shore to the
sea, there is apt to be a dearth of harbors. Only small
boats which can be dragged through the surf to the dry
land can be used, and so it comes about that the people
along such coasts usually make but limited use of the




ways of the ocean. On the other hand, in regions where
harbors abound, as along the northern coast of the
United States, both on its eastern and western faces, or
in the region of Northern Europe, Scandinavia, Holland,
and England, the people may become deep-sea sailors
and range over the oceans to the furthest lands of the
earth. These peculiarities of coast lines, whether they
afford good harbors or no, depend upon the ancient his-
tory of the shores. As we shall see further on, the sin-
gular abundance of harbors about the North Atlantic,
which have made the people of those lands the sailors
of the world, is immediately dvle to the fact that in for-
mer stages of the earth's development this part of the
coast was deeply carved by glaciers or streams of ice.
  If now we turn our attention from the industries of
men, which are related to the mere surface of the earth,
to the work which depends on the underground features,
we find a yet more striking instance of the effect brought
about by the ancient history of our sphere. Next after
the wealth which comes for man's use from the soil, we
must place that which comes from the mines. In look-
ing over a map of North America which shows the
mineral fields of the country, we observe that, although
more than half of its area has nothing of particular use
to man to be won from below the soil, there are large
districts where the under-earth is richly stored with a
great variety of materials to be gained by mining.
There are at present over fifty different substances of
great use to man which are obtained in one way or
another from the realm of the earth which lies below
the soil covering. Iron, copper, lead, zinc, gold, and sil-
ver, and several other valuable metals; coal, petroleum,
natural gas, materials which serve for light, warmth, and




the sources of powver; our building-stones; various sub-
stances which serve to fertilize the fields worn by crops;
and a host of other less important supplies for our arts
are derived from this nether realm.
  Wherever these mineral substances abound, the profit
from winning them is so considerable that often, to the
neglect of agriculture, the population seeks subsistence
from the deeper earth below the soil. Where these
substances are won, as in most cases they are, by delv.
ing deep beneath the surface, the men who follow these
pursuits become peculiar in their methods of life, their
ways of thought and action. These peculiarities of the
miner's life manifestly depend on the existence of par-
ticular substances in limited parts of the world. The
presence of these substances in the crust of the earth
depends upon the former history of the area in which
they lie; in a word, upon its old geographic conditions.
If the substance sought in the mine be coal, we know
that it is present, because in a very ancient day that
particular field was occupied by great swamps, in which
peaty matter was deposited in the manner in which
we may now see it accumulating in our ordinary bogs.
After a thick layer of peat was formed, the land it occu-
pied sank beneath the sea, and sand and clay were
accumulated upon it, which, while concealing it and pre-
serving it from complete decay, converted the mass to
coal. By further change it has been re-elevated, so that
it is accessible to man.  Ancient climate and ancient
geography, in other words, led to the production of the
coal bed. So with all the other substances won by the
miner; each owes its abundance in the particular field
to conditions of the climate or of the other geological
features which occurred in the past.




  It is hard to give the reader a clear idea as to the
intimate way in which the geography of the present day
determines the life now existing on the earth's surface;
yet it is important he should see something of these
facts, even if the instances he can consider are but few
in number. Perhaps the best illustrations of how closely
the life of the earth depends upon surrounding circum.
stances are afforded by field and garden plants. A
good example is found in the principal American grain,
-the maize or Indian corn, which furnishes by far the
most valuable grain crop of the continent. It is of the
utmost importance to the farmer to have a crop of this
corn; but in the northern parts of the tilled portion of
North America, generally in the region north of the
Great Lakes, the summer is too short for the plant to
mature its seeds. They are killed by frost before they
are fully developed. By carefully choosing each year
the plants which mature earlier than their neighbors in
the field, and using seed from these, varieties have been
formed which hasten their growth, and so in a measure
adapt themselves to the needs of the short northern
summer. The maize of Alabama requires five months
in its round from seed to seed ; by selection particular
varieties have been formed which will come to maturity
in regions where it is but three months between the
frost of spring and autumn. Further than this it seems
impossible to go, and so there is a limit determined by
the temperature beyond which the maize cannot be
grown with profit.
  The distribution of animals in the sea is even more
closely determined by the temperature than that of the
plants on the land. Thus in the warm waters south of
Cape Cod there are many kinds of animals which cannot




pass around this small cape into the colder waters of
Massachusetts Bay. The most vigorous and active fish
south of the Cape, the blue-fish, a creature there greatly
developed, cannot maintain itself north of the Cape.
Occasionally, in the last two centuries, it has in the
warmer seasons worked around the promontory, and for
a year or two gained a place in Massachusetts Bay. It
has seemed likely that it would permanently win this
new field, but each time it has been driven back by the
cold of the water. The difference is also marked in the
mollusca, or shell-fish; a number of species flourish just
south of the Cape, which do not appear in the some-
what colder waters a few miles to the northward. The
difference between the temperature of the waters north
and south. of Cape Cod is brought about by the influ-
ence of this small promontory, projecting only forty
miles from the main shore, on the movement of the
cold current which creeps down the coast of New Eng-
land and Nova Scotia from the Arctic regions, and
which is finally arrested in its movement by the hook
of Cape Cod.
  We need to comprehend these effects of differences
of a geographic sort, and conceive them as applying, in
a greater or less measure, to all living or extinct species
of animals and plants, in order to understand how far
the history of the earth in the past has served to affect
the beings of to-day, particularly the highest of them,
-man. Most animals and all plants are, as regards
heat, delicate thermometers.  They are affected, too,
by the winds, by the moisture of the air and soil, and
by the qualities of the soil itself, the plants directly,
and animals through plants; and so the world of life is
swayed about by every accident which affects these cir-




cumstances. Every geographic change alters the height
of the land or the shape of the sea, and thus affects the
currents of the air bringing heat and moisture, the
rivers which flow from the continents, or the marine
currents which convey the waters of the sea hither and
thither over its surface.
   The most important lessons which naturalists have
learned by the study of fossils contained in rocks con-
cern the succession of life in various stages of the earth's
history. At the present time there are somewhere
about half a million different kinds of animals and plants
on the surface of the earth.  Each species resembles
more or less closely other related species, so that we
have to look carefully to see the difference between
them, as, for instance, between the different kinds of
sparrows or the several sorts of oaks.  The greater
number of groups are separated in character by wider
differences, such as those which distinguish the beech
from the oak; but the white oak does not produce any-
thing but white oaks from its seed, and the sparrows
each rear broods of their own kind. If we search the
rocks which were formed on the earth's surface say half
a million years ago, - a very recent time in the earth's
history, - we find by the fossils they contain that there
were also oaks and beeches and sparrows, and these
were of species related to those now living, undoubtedly
the forefathers of living forms, but they differed from
them in most cases in a clear way: they differ as much
from living oaks or beeches as the species of these
plants now do from each other. Thus, stage by stage,
we can go back into the remote past of the earth, each
step separated, it may be, from the preceding by a mil-
lion years, until we have found somewhere near a hun-




dred different stages in the earth's history, each showing
by its fossils that the life, though akin to that which
went before and that which came after, had a particular
character.  Studying these facts, geologists have one
and all come to the conclusion that all the life of to-day
has come down to our time from ancestors of earlier
clays, and has indeed descended from the first beings
which came into existence on the surface of this sphere.
  A yet more important conclusion derived from the
study of these plants and animals of the past and their
relation to the living creatures of to-day is that, though
many kinds of animals have perished at various periods
in the past, leaving no descendants in our time, life
as a whole, both that of animals andl plants, has always
steadily been going upward in its organization towards
higher states of beirag.  If we consider the earlier
stages, -as, for instance, that known as the Cambrian,
which is near the time when life came upon the earth, -
we find in the fossils of the beds then laid down on the
sea-floor no fishes, no insects; only animals as lowly in
structure as our shell-fish, or worms, or certain kindred
of our crustaceans.  There were apparently no land
plants, only imperfect sea-weeds, or perhaps mosses and
lichens, on part of the continents which had arisen from
the sea. There were no lizards, frogs, birds, or four-
footed beasts of any kind.  The lands were probably
destitute of life, except for the lower kinds of plants and
perhaps for a few worm-like animals, or, it may have
been, the lowest grades of insects. In the latter chap-
ters of the great stone book, the leaves of which are the
strata or rock beds of the earth, we find stage by stage
the higher animals and plants appearing. First among
the plants come the fcruis, and then palm-like creatures,




and only in a relatively late day our flowering plants
and those which bear fruit and large seeds make their
appearance.  The back-boned animals also show the
same steadfast advance: first come the fishes; then,
after a long time, the reptiles; then the birds, at first
with long, lizard-like tails and teeth, then the higher
song birds. Sucking animals are wanting until a late
day; then they came with lowly forms related to the
kangaroo. Later, higher kinds appear; and finally the
history is rounded with the appearance of man.
  All the while these wonderful changes which have
led life upward in the scale of being have been going
on, the continents have been growing, slowly rising
from the sea-floor, gradually dividing the oceans into
separate seas, shaping the paths of rivers, and generally
determining the geographic influences which, as we have
seen, have so much to do with the conditions of life.
Every living species of plant and animal has been com-
pelled to move hither and thither with the changes in
the form of the land.  The more active kinds, those
which were better fitted to move here and there with
the changes in the land and the consequent alteration
of climate and other conditions, have lived because of
their vigor, of their intelligence, their power of associ-
ating their own action with that of other creatures; and
so in the changing geography of the earth the abler
forms survive and leave their strong progeny to inhabit
the world, while the weaker are destroyed through the
process of change.  Let us suppose that Cape Cod,
which, as we have seen, is an important geographic
feature affecting the climate of the sea-water on the
coast of the United States, were swept away, as it might
in a very easy way be removed by the waves. Then


           GEOGRAPHY OF NORTH AMERICA.             17

thcre would arise a contention between the creatures
living to the north and south of it as to which should
possess the portion of the coast formerly occupied by
the Cape.  The more vigorous would gain the ground,
and in this way a slight effect towards peopling the
earth with strong beings would be brought about. A
vast number of such changes, some of far greater mo-
ment, have tested the qualities of animals and plants,
their fitness to remain the masters of the earth. In
these trials the lowly and weak have been destroyed,
the higher and stronger have been preserved.
  It is very hard to tell the story of life in the past
within the limits of a few pages; but further on we
shiall try to see in the history of North America, in a
somewhat detailed way, how the advance of organic
life has been promoted by the successive and ceaseless
changes in the