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BERK
UNIVERSITY OF
CALIFORNIA
EARTH
SCIENCES
LIBRARY
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THE
GEOLOGICAL STORY
BRIEFLY TOLD.
Introtwrtion to
FOR
THE GENERAL READER AND FOR BEGINNERS
IN THE SCIENCE.
BY
JAMES D. DANA, LL.D.,
//
AUTHOR OF "A MANUAL OF GEOLOGY," " TEXT- BOOK OF GEOLOGY," "CORALS AND
CORAL ISLANDS," WORKS ON MINERALOGY, ETC.
WITH NUMEROUS ILLUSTRATIONS.
NEW YORK AND CHICAGO :
IVISON, BLAKEMAN, TAYLOR, AND COMPANY.
1875.
<n
I
& . te C&
COPYRIGHT, 1875.
BY IVISON, BLAKEMAN, TAYLOR, & CO.
UNIVERSITY PRESS: WELCH, BIGELOW, & Co.
CAMBRIDGE.
SCIENCES
LIBRARY
PREFATOET SUGGESTIONS.
EOLOGY is eminently an out-door science ; for strata, rivers,
\A oceans, mountains, valleys, volcanoes, cannot be taken into a
recitation-room. Sketches and sections serve a good purpose in illus-
trating the objects of which the science treats, but they do not set
aside the necessity of seeing the objects themselves. The reader who
has any interest in the subject should therefore go, for aid in his
study, to the quarries, bluffs, or ledges of rocks in his vicinity, and all
places that illustrate geological operations. At each locality accessi-
ble to him he should observe the kinds of rocks that there occur ;
whether they consist of layers or not ; and their positions, whether the
layers are horizontal, the positon they had when made ; or whether
inclined, a slope in the beds being evidence of a subterranean
movement like that which takes place in mountain-making.
Geology teaches that much the larger part of the rocks that con-
sist of layers were made through the action of water ; and if such
rocks are accessible, it is well, after learning the lessons of the book,
to look among them for evidence of this mode of origin, either in
the structure of the layers, in the nature of the material, in markings
within the beds, or in the presence of relics of aquatic life, such as
iv PREFATORY SUGGESTIONS.
shells, bones, etc. If some of the layers in a bluff consist of sand-
stone, others are pebbly, others clayey, and one or more are of
limestone, the kinds of changes in the waters that took place to pro-
duce so varied results should be made a point for investigation.
If an excavation for a cellar is opened near an accustomed
walk, it is best to look at the sections of the earth or sands thus
made ; for these sands are very often in layers, and, in that case, they
bear evidence that there even the loose material of the surface had
been arranged by water, either that of the ocean or that of a river
or lake.
When the layers contain fossils, a collection should be made for
study ; for they show what living species populated the waters or
land when the rocks were forming ; and in the height of a single
bluff there may be records thus made of several successive popula-
tions different from one another.
If a beach or a cliff along the ocean is accessible, the action of
the waves in their successive plunges may be watched to great ad-
vantage ; for they are thus grinding up the stones and sands of the
beach, and eroding and undermining the cliff. While viewing such
work on a seashore, it will be a good time to consider that this bat-
tering goes on almost incessantly through the year, and year after year,
and has so gone on along coasts and about reefs for indefinite ages.
The cliff and the rocky ledges in the surf at its base should be closely
examined, that the amount and kind of wear may be appreciated ; and
the action of the water over the beach should be studied in order
to understand why, after so much grinding, coarse sands and often
pebbles are still left.
PREFATORY SUGGESTIONS.
If there are sand-flats exposed off the shores at low tide, there
is a chance to discover by what currents or movements of the water
they were formed, and whence came the sands that compose them,
which should be taken advantage of; for they are identical in kind
and mode of origin, although not in extent, with the sand-flats of
ancient time out of which sandstones have been made ; the only pos-
sible difference being that in the earlier ages the waters were every-
where salt, and rivers gave little aid. And if the sandy surface is
left rippled as the tide goes out, note this, for ancient sandstones
often contain such ripple-marks over their layers ; or if the muddy
portions are marked with the tracks of Mollusks, note this also, for
in many rocks just such tracks occur.
If coral reefs or shell rocks are forming along the shores, as in
the West Indies, these formations should receive special study ;
for many of the old limestones of the world were made in the same
way.
If a heavy rain has gullied* a side-hill or proved disastrous to
roads, here is a fruitful field for study ; for the gullies are minia-
ture valleys, and they illustrate how most great valleys were ex-
cavated, the latter being as truly the work of running water as
the former. The same gullied slope may exemplify also the for-
mation of precipices and waterfalls, of crested ridges, table-topped
summits, and groups or ranges of mountain-peaks.
These are some of the points of easy observation. Many others
will occur to the reader after a perusal of the following pages.
A few labelled specimens of minerals and rocks are absolutely in-
dispensable for even a partial understanding of the subject, and the
vi PREFATORY SUGGESTIONS.
student should buy or beg them, if not able to do the better thing
of collecting them.
Of MINERALS: 1, crystallized quartz; 2, two or three quartz pebbles
of different colors ; 3, the variety of quartz called horustone or flint ; 4,
common feldspar ; 5, mica ; 6, black hornblende ; 7, a black or greenish-
black crystal of augite, and better if in a volcanic rock ; 8, garnet ; 9,
tourmaline ; 10, calcite (carbonate of lime), a cleavable specimen ; 11, dolo-
mite, or magnesian carbonate of lime ; 12, gypsum, or sulphate of lime ; 13,
pyrite (sulphid of iron) ; 14, magnetite, or magnetic iron ore ; 15, hematite,
or specular iron ore ; 16, limonite, the common iron ore often called "brown
hematite " ; 17, siderite, or spathic iron ore ; 18, chalcopyrite, or yellow
copper ore ; 19, galenite, or lead ore (sulphide of lead) ; 20, graphite.
Of ROCKS : 1, 2, 3, common compact limestone of three different colors,
one, at least, of the specimens with a fossil hi it ; 4, chalk, a variety of
compact limestone ; 5, 6, white and clouded granular or crystalline lime-
stone, of which the ordinary architectural marble is an example; 7, 8,
red and gray sandstone ; 9, conglomerate, called also pudding-stone ; 10,
shale, such as the slaty rock of the coal-formation, and other shales of the
Silurian and Devonian ; 11, slate, or argillyte, that is, common roofing-
slate, or writing-slate ; 12, 13, coarse and fine-grained grayish or reddish
granite (to be obtained, like marbles and sandstones, in many stone-yards) ;
14, red or gray syenyte, of which the Scotch " granite " and Quincy " gran-
ite " are good examples ; 15, gneiss, a piece that has the mica distinctly
in planes, and hence is banded on a surface of transverse fracture; 16,
mica schist; 17, trap, an igneous rock; 18, trachyte, an igneous rock;
19, lava, a cellular volcanic rock ; 20, a piece of diatom or infusorial earth.
The above-mentioned minerals should at least be accessible to a
class, if not in the hands of each student ; and it would be well if
PREFATORY SUGGESTIONS.
vn
the collection were larger. Moreover, the instructor, if not a prac-
tical geologist, should have by him the writer's Manual of Geology,
or some other large work on the science, in order to be ready to
answer the questions of inquisitive learners, and add to the exam-
ples and explanations.
The student should possess a hammer and a chisel. The best
hammer has the face square, flat, sharp-angled, and the opposite
end brought to an edge ; this edge should
have the same direction with the handle (as
in the figure), if it is to be used for get-
ting out rock-specimens, but be transverse
to this, and thinner, if for obtaining fossils.
The socket for the handle should be large, in order that the handle
may stand hard work. The chisel should be a stone-chisel, six
inches long. Rock - specimens should be uniform in size, with
straight sides ; say two inches by three, or three inches by four.
Fossils had better be separated from the rock if it can be done
safely.
For measuring the dip, that is, the slope, of layers, an instrument
called a clinometer is used, which can be had
of the instrument-makers. It is a compass
having a pendulum hung at the centre, the
extremity of which swings over a graduated
arc. In the best kind the compass is three
inches in diameter and has a square base. A
clinometer apart from the compass may be
easily extemporized by taking (see figure) a piece of board, abed,
viii PREFATORY SUGGESTIONS.
cut to an exact square (three or four inches each side), hanging a
pendulum on a pivot near one angle (), describing on the board,
with one leg of the dividers on the pendulum-pivot, an arc of 90
(b to c), and then dividing this arc into nine equal parts, each to
mark 10, and subdividing these parts into degrees. Such a cli-
nometer, well-graduated, is sufficiently accurate for good work.
Field work of the kind above pointed out makes the facts in the
science real. It also teaches with emphasis the great lesson that ex-
isting forces and operations are in kind the same that have formed
the rocks, the valleys, and the mountains. It thus prepares the
mind to appreciate geological reasoning and comprehend the march
of events in the earth's history.
NEW HAVEN, CONN., February 1, 1875.
TABLE OF CONTENTS.
PAGE
GEOLOGY 1
PART L ROCKS, OR WHAT THE EARTH IS MADE OF.
I. MINERALS 3
1. Consisting of Silica . , 3
2. Silicates 5
3. Carbon and Carbonates 8
4. Ores . .10
II. KINDS OP ROCKS 13
III. STRUCTURE OF ROCKS 19
PART II. CAUSES IN GEOLOGY, AND THEIR EFFECTS.
I. MAKING OF ROCKS 23
1. Ways in which Plants and Animals have contributed to Rock-
making 27
1. Making of Limestones 27
2. Making of Siliceous Rocks or Masses . . . .35
3. Making of Peat-beds 40
2. Quiet Work of Air and Moisture 42
3. The Work of Winds 44
4. The Work of Fresh Waters 46
5. The Work of the Ocean 50
6. The Work of Ice 57
7. The Work of Heat in Rock-making 63
1. Through Expansion and Contraction . . . .63
2. Through Fusion : Volcanoes 64
3. Solidification, Metamorphism, and Formation of Veins . 70
TABLE OE CONTENTS.
II. MAKING or VALLEYS . . . 76
III. MAKING OF HILLS AND MOUNTAINS AND THE ATTENDANT EFFECTS 80
1. Mountains made by Igneous Ejections 80
2. Mountains and Hills produced by the Erosion of Elevated Lands 81
3. Mountains made by Upturnings and Flexures of Rocks, and
Bendings of the Earth's Crust 83
PART III. HISTORICAL GEOLOGY.
SUBJECTS AND SUBDIVISIONS 96
I. ARCELEAN TIME . . . 106
1. Distribution . . . 10?
2. Rocks . : . , . , i' ; .... 109
3. Life ...-.".-..... . .111
II. PALEOZOIC TIME . .' . . . . . . . 113
1. Silurian Age, or Age of Invertebrates 113
1. Lower Silurian 115
2. Upper Silurian 129
3. Observations on the Silurian Age .... 134
2. Devonian Age, or Age of Fishes 137
1. Rocks 137
2. Life . . . . . . . . . . 139
3. Mountain -making ....... 148
3. Carboniferous Age, or Age of Coal Plants .... 149
1. Rocks. Coal-measures 150
2. Life 156
3. Changes during the Progress o the Carboniferous Age 164
4. Mountain-making at the Close of Paleozoic Time . . .167
Changes in Paleozoic Life at the Close of the Era . 173
III. MESOZOIC TIME . . 174
Age of Reptiles . 174
1. Rocks ......... 175
2. Life ':'.- ' 18
3. Mountain-making in Mesozoic Time .... 193
TABLE OF CONTENTS. xi
IV. CENOZOIC TIME 194
1. The Tertiary, or Age of Mammals 194
1. Rocks 195
2. Life 200
3. Mountain-making 206
4. Climate 209
2. Quaternary Age, or Era of Man 209
1. Glacial Period 211
2. Champlain Period 218
3. Recent Period 221
4. Life of the Quaternary 224
5. Geological Work still going Forward . . . .235
V. OBSERVATIONS ON GEOLOGICAL HISTORY 237
1. Length of Geological Time 237
2. Progress in Features 240
3. The System of Nature of the Earth had a beginning and will
have an end 241
4. Progress in Life 242
INDEX. 257
ILLUSTRATIONS.
THE original sources of the larger part of the illustrations will be found
stated in the author's Manual of Geology. Of the few not in the Manual,
Fig. 11 is from a photograph taken by the artist of Powell's, Expedition ;
Figs. 13 to 16, from the author's "Corals and Coral Islands"; Fig. 33,
from H. J. Clarke's " Mind in Nature " ; and Fig. 46, from an electro-
type kindly furnished by the publishers of the "American Naturalist,"
Salem.
GEOLOG-Y.
THE word Geology is from two Greek words signifying the
story of the earth. As used in science, it means an ac-
count of the rocks which lie beneath the surface and stand out
in its ledges and mountains, and of the loose sands and soil
which cover them; and also an account of what the rocks
are able to tell about the world's early history. By a careful
study of the nature and positions of rocks, and the markings or
relics they contain, it has been discovered how the rocks them-
selves were made; and also how the mountains and the conti-
nents, with all their variety of surface, were gradually formed.
And, further, it has been ascertained not only that the earth had
plants and animals long before Man appeared, but what were
the kinds that existed in succession through the long ages.
The subjects, therefore, of which geology treats are :
I. The KINDS OF ROCKS.
II. The ways in which the rocks, valleys, mountains, and
continents were made, or CAUSES IN GEOLOGY, AND THEIR
EFFECTS.
GEOLOGY.
III. The events during the successive periods in the earth's
history; that is, what making of rocks was going on in each
period, what making of mountains' and valleys, and what spe-
cies were living in the waters and over the land in each, and
how the world of the past differs from the world as it now is,
all of which subjects, and others related, are treated under the
general head of HISTORICAL GEOLOGY.
PART I.
ROCKS, OR WHAT THE EARTH IS MADE OF.
BOCKS consist of minerals ; and the ores and gems they con-
tain are minerals. Any mineral that yields a metal profitably is
called an ore.
The following are the characters of some of the kinds that
are of most importance in geology.
i
I. Minerals.
I . Consisting of Silica.
Quartz. Quartz is the most common of the materials of
rocks. It is well fitted for this first place ; for (1) it is one of
the hardest of minerals, the point of a knife-blade or edge
of a file making no impression on it; (2) it does not melt in
the hottest fire ; and (3) it is not dissolved by water, or cor-
roded by either of the common acids. Its durability is its
great quality. "With a piece of quartz it is easy to write one's
name on glass. Another quality of it, distinguishing it from
many minerals it resembles, is that it breaks as easily in one
direction as another.
4 ROCKS, OE WHAT THE EARTH IS MADE OF.
It is of various colors and kinds. Flint and hornstone are
dark-colored massive quartz. The smooth-surfaced stones of a
pebble-bank, whether white, brown, yellow, or black, if uni-
form (not speckled) in color, are almost all quartz. Moun-
tains thousands of feet high are sometimes made of quartz
rocks. The sands of a sea-shore are mostly quartz, because the
grinding of particle against particle which goes on under the
heavy dash or swift flow of the waters wears out all other
materials, and leaves only the hard quartz particles behind.
Quartz is often found in crystals. The figure annexed shows
the form of one of them. It is a regular 6-sided prism (i i i),
Fig. i. with a 6-sided pyramid at each end ; and it is often
as transparent as glass. Frequently the crystals are
attached by one end in great numbers to a surface
of rock, so that this surface is brilliant with little
Quartz. pyramids of quartz set crowdedly over it, or with
pryamids raised on prisms. The inclination of the face of the
prism to the adjoining face of the pyramid is always the same
(141 47'), wherever the quartz crystal may come from. These
glassy crystals are wholly natural productions, having their
forms perfect and lustre brilliant when first taken from the
rocks.
While some quartz crystals are clear and colorless, others
have a purple color, and these are the amethyst of jewelry.
Others have a light-yellow color, looking like topaz, and are
called false topaz ; and others a clear smoky-brown color, and
these are the cairngorm stone of Scotland.
MINERALS CONSTITUTING ROCKS.
Still other kinds of quartz are the agates, in which the color
is arranged in thin bands or layers of different shades of color,
as white, smoky-brown, red, etc.
The material of quartz is called in chemistry silica, from the
Latin word silex, meaning flint.
Quartz, while so enduring, when pulverized and heated fuses
easily with soda, potash, lime, magnesia, or oxyd of iron, and
forms a kind of glass; and ordinary glass is made by melting
together quartz sand and soda. Again, hot waters containing
soda or potash in solution will dissolve silica, and on cooling
deposit it again. The waters of hot springs usually contain
silica, which they have taken, along with soda or potash, from
some rock with which they have been in contact. Through
deposits from such solutions (1) agates have been made; (2)
fissures in rocks have been filled with quartz, and the fractures
thus mended; and (3) the sands of sand-beds and gravel of
gravel-beds have often been cemented into the hardest of rocks.
Opal is also silica, but it differs from quartz in being softer,
of less specific gravity, and never crystallized ; and in %e
precious opal it has a beautiful play of colors arising from
internal reflections. The silica of diatoms and of some de-
posits made by geysers is in the state of opal.
2. Silicates.
Silica, while existing in rocks abundantly as quartz, also
makes, on an average, a third of all their other minerals,
C ROCKS, OR WHAT THE EARTH IS MADE OR
limestones excepted; that is, it exists combined with other
substances, making various common minerals. These minerals
containing silica are called silicates.
L Feldspar, The most universal of these silicates are the
kinds called feldspar. Besides silica, a feldspar contains the
elements of alumina, and of potash, soda, or lime. Corun-
dum is nothing but alumina ; and the beautiful gem sap-
phire is only a clear blue variety of it; and the hard emery
used for grinding and polishing, and often in little emery-
bags for sharpening needles, is the same. It is the hardest
of all stones excepting the diamond, and hence it is a good
companion for quartz or silica in rock-making. The two,
silica and alumina, in combination together make minerals
that are harder and no less infusible than quartz; but when
combined also with potash, soda, lime, or iron, the minerals
it forms melt more or less easily.
Feldspar has usually a white or flesh-red color, and some-
times might be mistaken for quartz. But (1) it is not quite
so hard as quartz, though too hard to be scratched with a
knife; and, besides, (2) it melts when highly heated; (3) it
breaks in one direction with a bright even surface, brilliant in
the sunshine, and also in another direction at right angles
or nearly so to the former, but less easily, a kind of
fracture called, in mineralogy, cleavage. While quartz has
no cleavage, feldspar has cleavage in two directions trans-
verse to one another.
MINERALS CONSTITUTING ROCKS.
Common feldspar (called orthoclase in mineralogy) is a pot-
ash-feldspar, it containing the elements of potash along with
those of alumina and silica ; another is a soda-feldspar
(albite) ; others are soda-and-lime feldspars, and one of these,
called labradorite, is a constituent of many igneous rocks ;
and another is a lime-feldspar.
2. Mica. Mica (often wrongly called isinglass) splits very
easily into leaves thinner than the thinnest paper, which are
tough and elastic, and frequently transparent. It does not
melt easily, but fuses on the thin edges with high heat. It
is the transparent material commonly used in the doors of
stoves. Some mica is white, or gray; it is oftener brownish,
and very frequently black. Like feldspar, it contains the
elements of silica and alumina; the most common light-col-
ored kind has, besides these constituents, potash ; the black
kind contains magnesia and iron.
3. Hornblende. Black hornblende, when occurring in
rocks, often looks much like mica, showing lustrous cleavage
surfaces; but it is a brittle mineral, and hence cannot, like
mica, be split into thin, flexible leaves or scales with the
point of a knife. It makes very tough rocks, and hence the
first part of the name, horn; the rocks are heavy and some-
times look like an ore of iron, and hence the second part,
blende, a German word meaning blind or deceitful. It is
a silicate, that is, it contains silica, but with it there are
iron, magnesia, and lime. There are other kinds of hornblende,
but they need not be mentioned here.
8 ROCKS, Oil WHAT THE EARTH IS MADE OF.
4. Augite. Augite is black or dark-green pyroxene, hav-
ing the same composition as hornblende, and differing only in
the shape of its crystals. It is named from a Greek word
signifying lustre, because its crystals are often bright, though
not more so than those of hornblende.
Two of the crystals of hornblende are represented in Figs.
2, 3, and one of those of augite in Fig. 4. The angle of
Figs. 2-5.
Minerals.
Figs. 2, 3, Hornblende ; 4, Augite ; 5, Garnet in mica schist
the prism of augite (or that between / and / in Fig. 4)
is about 87; while the angle of the prism of hornblende (be-
tween / and I in Fig. 2) is 124^ ; it is owing to this differ-
ence mainly that hornblende and augite have distinct names.
5. Garnet Usually in dark-red crystals, but often also
black, and occurring imbedded in mica schist and other rocks ;
as represented in Fig. 5, contains silica, alumina, iron, and
lime. When transparent it is used as a gem.
3. Carbon and Carbonates.
Carbon is familiarly known, though in a state not quite
pure, as common charcoal. The diamond is crystallized car-
MINERALS CONSTITUTING ROCKS. 9
bon, and can be burnt like charcoal, though not without in-
tense heat. Graphite (or black lead, as it is often badly
named, since it contains no lead) is also carbon; it is the
material of lead-pencils.
Carbon combined with oxygen in certain proportions forms
carbonic acid, an ingredient of the atmosphere, it constituting
4 parts by volume of 10,000 parts of air; it is the gas that
escapes from effervescent waters like soda-water. Its com-
pounds are called carbonates.
L Calcite. Calcite occurs in crystals that break easily in
three directions, affording forms with rhombic faces, like Fig.
6; the angles between the faces are 105 5'
If IgS. O O
and 74 55'. A very common form is called
dog-tooth spar ; the shape is shown in Fig.
7. Another kind is a 6-sided prism with
a low pyramid at either end (Fig. 8). Cal-
cite is easily scratched with the point of a
knife. In a rock form, it is limestone.
When calcite or limestone is burnt, carbonic acid escapes as
a gas, and lime (called quicklime, the material that slacks
in water and is used for making mortar) is left. Calcite is
carbonate of lime. When a grain of calcite is put into di-
lute hydrochloric (muriatic) acid, carbonic acid gas is given
off freely, producing a brisk effervescence, and the calcite be-
comes wholly dissolved if it is pure. By means of (1) its
effervescence with acid, (2) its low degree of hardness, (3)
i*
10 ROCKS, OR WHAT THE EARTH IS MADE OF.
its infusibility in the hottest fire, and its burning to quick-
lime instead, calcite or limestone is easily distinguished from
feldspar and other minerals. The cleavages in calcite also
separate it from feldspar; for the number of directions is
three, and the angle between them is about 105 instead of
about 90.
2. Magnesian Limestone, or Dolomite. Limestone sometimes
contains magnesia in place of part of the lime, and it is then
called, in mineralogy, dolomite, after Dolomieu, a French
geologist of the last century. Dolomite, or magnesian lime-
stone, does not effervesce freely unless the acid is heated, and
in this respect it differs from calcite. In aspect, calcite and
dolomite are closely alike.
4. Ores.
The following are a few of the common ores.
1 Pyrite. Pyrite has nearly the color and lustre of brass.
It is so hard that it will strike fire with steel (whence its name,
from the Greek for fire), and in this it differs from a yellow
ore of copper, called chalcopyrite or copper pyrites, which
it much resembles. It is very often in cubes,
Fig. 9.
like Fig. 9. It consists of sulphur and iron,
nearly 48 parts by weight in 100 being iron.
Both of these elements have a strong affinity
for oxygen; and consequently pyrite often changes
to vitriol, or else forms the oxyd of iron called limonite.
MINERALS CONSTITUTING ROCKS. 11
It is of no use as an ore of iron, because of the difficulty
of separating the sulphur; but it is often employed for the
making of vitriol (sulphate of iron). It is the most gener-
ally distributed of all metallic minerals, occurring in particles
through most rocks, crystalline as well as uncrystalline. Ow-
ing to the tendency to alteration just mentioned, it has caused
the destruction or disintegration of rocks over the earth's sur-
face to a greater extent than any other agency.
2. Magnetite, or Magnetic Iron Ore, An iron-black ore
of iron, having a black powder. It is attractable by the mag-
net. It is common in Northern New York, Orange County,
New York, Sussex County, New Jersey, and many other
regions. It consists of oxygen and iron in the proportion
of 4 atoms of the former to 3 of the latter, and contains
72 parts of iron in 100.
3. Hematite, or Specular Iron Ore. A steel-gray ore of
iron, but often also bright red, the powder being red. Bed
ochre is an earthy hematite. It is not attracted by a mag-
net. Like magnetite, it occurs in great beds in Northern
New York, in the Marquette region, near Lake Superior, in
Michigan, and many other places. It consists of oxygen and
iron in the proportion of 3 atoms of the former to 2 of the
latter, and contains, when pure, 70 parts by weight of iron
in 100.
All rocks of a reddish or red color owe the color to this
oxyd of iron.
12
ROCKS, OB WHAT THE EARTH IS MADE OF.
Hematite and magnetite occur, with -all exceptions, in
beds instead of veins. When the beds are verbal or nearly
so they look like veins.
I Lonite.-A brown, brownish-yellow, or black ore of
mn , affording a Iro^-yello* powder, sometimes eal
, Yellow ochre is impure or earthy 1 .
It differs in composition from hematite only in contanung wa-
r . and if heated the water is dnven off, and * becomes
red ' or hematite. It contains, when pure, about 60 per cent
of | ro n It is a result of the decomposition of other won ores,
nd fonns great beds in some regions, as near Salisbury ,n
Connecticut, and Richmond in Massachusetts. It , often found
in bogs, and is then called log-iron ore. Lunomte
disseminated through clays, giving them a yellowish or brown
ish color; and such clays when heated turn red, because thy
1 the water which makes limonite to differ from hemat^
This is the reason that bricks are usually red. Clay
*ti
bonicacid. When pure about 48 parts
occurs crystallized, and also in impure massrve nodular form.
The iron ore of many coal.regions is thi, mass.ve nodule
SsK
grayish or browmsh stones.
KINDS OF ROCKS. 13
effervesces, owing to the escape of carbonic acid. This ore,
like limonite, is sometimes present sparingly in clays.
6. Chalcopyrite, or Yellow Copper Ore. A brass-colored
mineral consisting of sulphur, iron, and copper, about a third
of which is copper. It is scratched easily with a knife, and
affords a dark-green powder, and thus differs from pyrite,
which it resembles. It occurs for the most part in veins
with other ores.
7. Galenite, or Lead Ore. A lead-gray ore, brittle and
easily pulverized, and affording a lead-gray powder. It often
cleaves into cubic or rectangular forms. It is the common
lead ore. It often contains a little silver, and is sometimes
worked as a silver ore. It occurs in cavities in limestones,
as in Northern Illinois, Wisconsin, and Missouri, and in Der-
byshire, England ; and is often found also in veins with
other ores.
II. Kinds of Rocks.
THE following are the characters of some of the common
kinds of rocks.
1. Limestone ; Magnesian Limestone. These rocks are partly
described on pages 9 and 10. They are of dull shades
of colors, from white through gray, yellow, red, and brown
to black, and of all degrees of texture, from that of flint to.
a coarse granular texture. The test by acids, by heat, and
by a use of the point of a knife in trial of the hardness,
14 ROCKS, OK WHAT THE EARTH IS MADE OF.
are the means of distinguishing limestones from other rocks.
Chalk is limestone. Ordinary marble is limestone, and some-
times the magnesian kind.
The different kinds of limestone are called calcareous rocks,
from the Latin calx, meaning lime.
2. Sandstone. Sandstone is a rock made of sand. The
sand may be quartz, like the sand of most sea- shores, or
pulverized granite or other rock; when gathered into beds
and consolidated, it makes sandstone. Sandstones are the most
common of rocks. They have various dull colors, from white
through gray, yellow, and brown to brownish-red and red.
3. Conglomerate. A conglomerate or pudding-stone is a
consolidated gravel-bed, gravel being sand mixed with peb-
bles or small stones. The stones are sometimes large, even a
foot in diameter. They are often of quartz, sometimes of
other hard rocks, and occasionally of limestone.
4. Shale. Shale is a fine mud or clay consolidated into
a rock having a slaty fracture, but less evenly slaty and
less firm than true slate. The colors vary, like the colors
of mud or clay, from gray and yellowish shades through red
and brown to black. Black is a common color, because the
plants and animals that live and die in the mud or over it
contain carbon, the chief element of coal, and contribute por-
tions of carbonaceous substances to the mud. Such black
shales, when burnt, usually become white or nearly so, because
the vegetable or animal material is then burnt out. For
the same reason black limestones afford white quicklime.
KINDS OE ROCKS. 15
The loose earthy material of the world, in and out of the
water, is mostly either sand, gravel, mud, or clay; and thus
it has been through all ages. Sand is finely pulverized rock.
Mud is the same, for the most part; but it may contain
rock that is decomposed as well as pulverized. Clay is a
fine kind of mud; it is mainly either pulverized feldspar
along with quartz in fine grains, or else decomposed feldspar
with more or less quartz. It comes from the pulverizing of
granite, gneiss, and other rocks containing feldspar, or from
their decomposition. Clay often contains iron; and when
burnt to make brick it then becomes red. Gravel is mixed
sand and pebbles.
The consolidation of sand makes sandstones; of pebble-
beds, conglomerates; of fine mud or clay, shale.
5. Argillaceous Sandstone. When sands are clayey, the
beds make, when consolidated, a clayey, that is, argillaceous,
sandstone (argilla, in Latin, meaning clay). Such sandstones
usually break into thin slabs, in which case they are said to
be laminated sandstones; and, if of sufficient hardness, they
make good flagging-stone for sidewalks. The common flag-
ging-stone used in New York and adjoining States is an
argillaceous sandstone.
6. Slate. Slate, or argillyte, differs from shale in break-
ing much more evenly, and being much firmer. The slates
used for roofing are examples.
7. Granite. Granite is one of the crystalline rocks, its
16 ROCKS, OR WHAT THE EARTH IS MADE OF.
ingredients being, not worn grains like those of a sandstone
or conglomerate, but crystalline grains, all having been
rendered crystalline together by a process in which heat was
concerned (p. 26). It consists of grains of three minerals,
quartz, feldspar, mica, mixed promiscuously together. The
quartz grains are usually grayish or smoky in color (com-
monly of a darker tint than the feldspar), and have no cleav-
age. The grains of feldspar have cleavage, and therefore
show smooth, sparkling surfaces when a fragment of granite
is exposed to the sun, and their color is usually white or
flesh-red. The mica is much softer than the feldspar, and
with a point of a knife-blade its grains may be divided into
thin, flexible scales; its colors are white, brownish, or black.
8. Gneiss. Gneiss has the same constituents as granite;
but these constituents are arranged more or less in planes,
and, owing to the mica, the rock splits into thick layers, and
on a cross fracture appears banded. On account of its split-
ting into layers gneiss is said to be a schistose rock (this
term being derived from a Greek word meaning to divide, and
pronounced as if spelt shistose}. This schistose structure is
the only one distinguishing it from granite. It is somewhat
like the laminated structure.
9. Mica schist. Mica schist has the same constituents as
granite and gneiss, but the quartz and mica are much the
most abundant, and especially the mica; and on account of
the large proportion of mica, mica schist divides into thin
KINDS OF ROCKS. 17
layers. It glistens in the sunshine, owing to the scales of
mica. Sometimes the scales of mica are indistinct, and then
it is called mica slate.
The crystalline rocks, granite and gneiss, and gneiss and
mica schist, pass into one another through indefinite shadings.
There are granites that are slightly gneiss-like, and all
grades to true gneiss; and there are all grades from gneiss
to mica schist, so that it is sometimes difficult to say
whether a rock should be called granite or gneiss, and
whether another should be called gneiss or mica schist.
Again, mica schist shades off through mica slate into argil-
lyte, or clay slate, as the crystalline texture is less and less
apparent.
10. Syenyte. Some granite-like rocks contain hornblende
in place of the mica, and such kinds are called syenyte. The
hornblende is grayish-black, greenish-black, or black, and
differs from black mica in being brittle, and hence in not
affording thin, flexible scales. This fact indicates the kind
of examination to be made to distinguish syenyte from
granite. The so-called granite of the Quincy quarries, near
Boston, and the red Scotch granite imported for monuments,
are syenyte.
II Syenyte Gneiss ; Hornblende Slate. Syenyte gneiss differs
from ordinary gneiss in containing hornblende instead of
mica. Hornblende schist or slate is a black slaty rock con-
sisting mainly of hornblende.
B
18 ROCKS, OR WHAT THE EARTH IS MADE OF.
12. Trap; Volcanic Eocks, Trap is an igneous rock: that
is, it has cooled from fusion, like the lavas of a volcano.
It came to the surface in a melted state, through an opened
fissure, from some deep-seated region of liquid rock. The
part filling a fissure is called a dike. It has sometimes
flowed from the fissure over the adjoining country. Trap
is a dark-colored, heavy rock, more or less crystalline in tex-
ture. It consists of a lime-and-soda feldspar (called labra-
dorite, from Labrador, where it was first found) and augite,
along with grains of magnetite. It is the rock of the Pali-
sades along the west side of the Hudson River above New
York, of Mount Holyoke near Northampton, and various
other hills and ridges in the Connecticut Valley; of many
ridges in the vicinity of Lake Superior, and over the west-
ern slope of the Rocky Mountains; of the Giant's Causeway
on the north coast of Ireland, and Staffa on the western
coast of Sco'tland; and is common over the globe.
Some trap contains small nodules consisting of different
minerals. These nodules fill cavities that were made, while the
rock was still melted, by expanding vapors. This variety of
trap is called amygdaloid, because the little nodules sometimes
have the shape of almonds (amygdalum, in Latin, meaning
almond}. Trap, especially if very fine grained, is often called
basalt. It frequently occurs in columnar forms, as at the
Giant's Causeway, many places in the Lake Superior region,
and elsewhere.
STRUCTURE OF ROCKS. 19
Volcanic rocks, called lavas, are those that have been ejected
in a melted state from, or about, an open vent called (from the
Latin for bowl) a crater. Eruptions around the crater make
the fire-mountain, or volcano.
The larger part of lavas, and of all igneous rocks, are simi-
lar in composition to trap, although often very cellular rocks,
and sometimes resembling much the scoria of a furnace.
Other volcanic and igneous rocks are mainly feldspar in
composition, and as they therefore contain little or no iron,
they are less heavy than trap. Their specific gravity is mostly
2.5 to 2.8, while that of the trap series is 2.8 to 3.2. A com-
mon kind, rough on a surface of fracture, is called trachyte;
and another, containing isolated crystals of feldspar, is porphyry.
Sand-rocks made out of volcanic sands are called tufas.
III. Structure of Rocks.
L Stratified Rocks. Most rocks consist of layers piled one
upon another; and the series in some regions is thousands of
feet in height. Figure 10 rep-
resents a bluff on the Genesee
River at the falls near Roches-
ter. In this section Nos. 1 and
2 are sandstone; No. 3, green
i -I - T , , . -- Section on Genesee Kiver.
shale; No. 4, limestone; No. 5,
shale; No. 6, limestone; No. 7, shale; No. 8, limestone again.
20 ROCKS, OR WHAT THE EARTH IS MADE OF.
Fisr. 11.
Part of the wall of the Colorado Canon, from a photograph by Powell's Expedition.
Another example is here presented (Fig. 11) from the Colo-
rado Canon. The height of the pile of layers in view is over
3,110 feet; but the river flows 2,755 feet below, and hence
the whole height of the wail is 5,865 feet. Still another
example from the Colorado region is given on page 78.
It is to be noted that (1) the layers were made one after
another, beginning with the lowest; that (2) the successive
layers correspond to successive intervals of time in geological
history.
STRUCTURE OF ROCKS. 21
Eocks consisting thus of beds are called stratified rocks,
from the Latin stratumj meaning bed.
But layer and. stratum in geology have not the same mean-
ing. In Fig. 10 the lower sandstone bed, No. 1, consists
of many layers; together they make a stratum. No. 3 is
another stratum, one of shale; No. 4, another, one of lime-
stone, and also made up of many layers; and so on. Thus
there are eight strata (strata being the plural of stratum] vis-
ible in the bluff; and each consists of many layers. All the
layers of one kind, lying together, make one stratum.
Sandstone, shale, conglomerate, and limestone are the- most
common kinds of stratified rocks. Gneiss and mica schist are
also of this nature, although crystalline in texture.
2. TTnstratified Rocks. Unstratified rocks are not made up
of layers. The granite about the Yosemite, in California, is in
lofty mountains and mountain-domes, showing no distinct bed-
ding or stratification; and the same is the character of most
granite. The trap-rocks of the Palisades, on the Hudson, rise
boldly from the water and have no division into layers; but,
instead, a vertical division into imperfect columns, a com-
mon feature of such trap-rocks, illustrated on the next page. It
is not, however, true that all igneous rocks are ^stratified ; for
where lavas have flowed out in successive streams over a region,
those streams have made successive beds, and the rocks are
truly stratified. But the term stratified rocks is usually
applied only to the kinds not of igneous origin.
22
HOCKS, OR WHAT THE EAKTH IS MADE OE.
The columnar structure of some trap-rocks is well illustrat-
ed in the following view of a scene on the shores of Illawarra
Fig. 12.
Basaltic columns, coast of Illawarra, New South Wales.
in New South Wales, Australia. While stratification has come
from the successive formation of beds,, these columns are a
result of the cooling. Cooling causes contraction, and the
contraction of the solid rock as cooling went on produced
the fractures. These fractures are always at right angles, or
nearly so, to the cooling surfaces. Where the rock fills ver-
tical fissures, the columns are horizontal. Even sandstones
have been rendered columnar where overlaid by beds of trap,
or when they have been subjected otherwise to heat.
PART II.
CAUSES IN GEOLOGY, AND THEIR EFFECTS.
UNDER the head of Causes, Geology treats of the ways
in which (1) rocks, (2) valleys, (3) mountains and continents
were made; or, in general, the means through which all
changes have been brought about.
I. Making of Rocks.
THE rocks, briefly described in the preceding pages, have
been made by the following methods.
L Rocks formed from fusion. Igneous rocks are here in-
cluded, or those that have cooled from a melted state after
ejection from some seat of fire within the earth. They are
crystalline in texture, each grain being a separate crystal;
yet the small grains are so crowded together that they have
nothing of the external forms of crystals, and sometimes they
are too minute to be easily distinguished. Igneous rocks are
of small extent and importance over the globe compared with
those made through the action of water.
2. Rocks made by deposition from waters holding the mate-
24 CAUSES AND THEIR EFFECTS.
rial of them in solution. Waters containing lime often de-
posit it, and so make a kind of limestone.
Waters percolating through the limestone roofs of caverns,
as they evaporate on the roof, form long pendent cones or
cylinders of limestone called stalactites (from the Greek for
to distil) ; and the same waters, dropping to the floor of the
cavern, there evaporate and produce a bed of limestone called
stalagmite.
There are many springs, and a few rivers, in the world,
whose waters are calcareous. They petrify the moss, leaves,
and nuts of swamps, and sometimes make thick beds which
are very porous, and irregular in thickness and texture, called
calcareous tufa, and also travertine. On Gardiner's Eiver, in
the Yellowstone Park, at the summit of the Rocky Mountains,
such deposits are forming, and the river is thus made into
a series of waterfalls. But such beds of limestone are of
even less extent and importance than igneous rocks. None
of the great limestones of the world were thus made.
Waters often hold traces of silica in solution, especially
if hot and alkaline, and deposit it again, making siliceous
beds and petrifactions. Some facts on this point are men-
tioned beyond, among the eifects of heat in rock-making.
Cold water seldom deposits silica unless where there are
the remains of siliceous infusoria, as mentioned on page 38.
3. Rocks made by the mechanical agency of waters and
winds, exclusive of limestones. Par the larger part of rocks
MAKING OF ROCKS. 25
are fragmental rocks ; that is, they are rocks made out of
fragments of older rocks. The finest mud or clay consists
of fragments of rock-material, and hence a shale a rock
made from fine mud or clay is a fragmental rock as
much as a sandstone or conglomerate.
A large part of the fragments or the sand, pebbles,
mud - were made by the wearing action of moving waters ;
and hence such material is called detritus, from the Latin,
meaning worn out. The agency of greatest effects and long-
est action in past time has been the ocean; that of next
importance, rivers ; that next, winds. But, preparatory for
these agencies, the air, moisture, and the sun's heat have
been always quietly at work giving aid in the reduction of
rocks to fragments or grains; and thus the ocean, rivers, and
winds have found much loose material ready for them, in-
stead of being left to make all that was required for their
work in rock-making.
The sand, gravel, and mud or clay of which rocks have
been made were in general deposited as a sediment from the
waters of the ocean or rivers, as will be explained further
on ; and hence sandstones, conglomerates, and shales are called
sedimentary rocks.
4. Rocks made mainly or wholly of organic remains, that
is, of the remains of plants or animals, (1) The great lime-
stones of the world are of this origin ; also (2) some sili-
ceous deposits; and (3) the coal-beds and peat-beds of the
26 CAUSES AND THEIR EFFECTS.
world. Many sandstones and shales contain more or less of
such remains. Plants, shells, and other distinguishable relics
of living species found in rocks are called fossils, or organic
remains. They are sometimes called also petrifactions, which
means made of stone ; but not always rightly so, for most
fossils consist of the same material essentially that they had
when in the living species. Wood is sometimes changed to
stone; and this is then a true petrifaction.
5. Metamorphic Rocks. Fragmental rocks, such as sand-
stones, shales, and conglomerates, and also limestones, have
sometimes been altered (or metamorphosed), over regions of
great extent, to crystalline rocks, such as granite, gneiss,
mica schist, granular limestone or architectural marble; and
these crystalline rocks are hence called metamorphic rocks,
the word metamorphic meaning altered.
In describing these methods of making rocks the following
order is here adopted :
1. The ways in which plants and animals have contributed
to rock-making.
2. The results from the quiet working of air and moisture.
3. The work of winds.
4. The work of rivers.
5. The work of the ocean.
6. The work done by ice.
7. The work of heat.
LIMESTONE ROCKS OE ORGANIC ORIGIN.
I. Ways in which Plants and Animals have contributed
to Rock-making.
1. Making of Limestones.
The animal relics that have contributed most to limestones
are shells, corals, crinoids, and foraminifers. These are secre-
tions of animals, that is, stony portions of the body, either
made internally in the same manner as the bones of a dog are
made, or, like a shell, made externally as a covering for the
animal. When the animal dies, the relics pass to the mineral
kingdom and are used in rock-making ; and, as stated above,
nearly all the limestones have thus been made.
Corals and crinoids are exclusively oceanic species of ani-
mals ; but, while this is true also of most shells and fora-
minifers, there are some kinds that nourish in fresh waters,
and among shells some, like the snail, live over the land.
Shells are the secretions of animals related to the oyster,
clam, snail, and cuttle-fish, animals that have a soft fleshy
body, and hence are called Mollush, from the Latin mollis,
soft. The shells serve to protect the soft body and give it
rigidity.
Coral is, for the most part, the secretion of polyps, the
most flower-like of animals, and it is an internal secretion.
One of the branching corals, covered over (one branch ex-
cepted) with its numerous little flower-animals, is represented
in Pig. 13. Branching corals of this nature are common in the
28
MAKING OF ROCKS.
tropical Pacific, and are called Madrepores. Another kind, mas-
sive instead of branching, is shown in Eig. 14. The whole
surface is a surface of flower-animals or polyps; in reference
to its star-like cells, this kind is called an Astraa. The
Fig. 13.
Madrepora aspera D.
expanded animals (only part of which in the figure are in this
state) are like flowers also in their bright colors. The little
petal-like arms (tentacles), in Pig. 13, are tipped with emerald-
green, in the living state; and some Astrseas are purple or
LIMESTONE ROCKS OE ORGANIC ORIGIN.
Fig. 14.
Fig. 15.
Astraea pallida D.
crimson with an emerald centre,, and others have other bright
tints. "While so much like flowers in appearance, polyps are
wholly animal in nature. Each polyp has a mouth at the
centre above, as shown in Pig. 14;
and it eats and digests like other
animals. Another kind of coral is
represented in Fig. 15, without the
animal; it shows the radiating plates
in the cup-shaped cavity at top. Still
another, somewhat larger, elliptical in
shape instead of cylindrical, and in the
living state, is presented in Fig. 16.
The mouth is a very long one, and
the arms or tentacles which serve to push in the prey it cap-
Thecocyathus cylindraceua
Pour-tales.
30 MAKING OF ROCKS.
tures are also long. It owes much of its power of capturing
to the stinging qualities of these tentacles.
The arrangement of the tentacles of a polyp around a
centre, and also that of the plates inside of the coral cup, is
radiate; and hence Polyps, like some other kinds of life, are
called Radiate animals.
Tig. 1C.
Flabellum pavoninum.
Crinoids. Crinoids also are flower-like animals, and Radi-
ates. They were once exceedingly abundant in the seas of the
world, but now are rarely to be found. Two of the kinds are
represented in Figs. 17 and 18, the first an ancient species,
and the second a modern one from the seas of the "West Indies.
The arms above are arranged around a centre like the petals
of a flower, and, like them, they may be opened out wide or
closed up so as to look like a bud; and this the animal does
at will. Below the radiating head-bearing part there is a
stem, sometimes a foot or more long, which, if the animal is
LIMESTONE ROCKS OF ORGANIC ORIGIN.
31
alive, is planted below on the solid rock, or in the mud of the
sea-bottom. Crinoids differ in many respects from polyps.
One point is this : the coral which a polyp makes is all one
Figs. 17, 18.
Crinoids.
Fig. 17, Zeacrinus elegans ; 18, Pentacrinus caput-Medusae, now living in the West Indies; a~d, calcareous
disks or plates of the stem, showing their s-sided form.
piece, whether massive or branching; while the stony secretion
of the crinoid is in multitudes of pieces. The stem is a pile
of little disks often circular and looking like button-moulds,
as in Eig. 17; but sometimes 5-sided, as in Pigs. 18 a, b, c, d,
showing some of the forms. The arms also are made up of
stony pieces. The cross-lines on the arms in the above figures
indicate the number of pieces of which each is made. The
pieces are held together by animal membrane as long as the
animal lives ; but when it dies, the pieces usually fall apart,
and are scattered by the moving waters.
MAKING OF ROCKS.
Foraminifers. Foraminifers are made by the simplest of
all animals, and very minute kinds, animals that have no
organs of sense, and in general not even a mouth to eat with.
When a particle of the desired food touches the body, and is
perhaps held there by its power of stinging, that part of the
body begins to be depressed, and continues to sink inward
until the food is in a cavity inside made for the occasion;
then the food is digested, and any part of it not digested is
thrown out by restoring the body to its former state. Some
Rhizopods.
Fig. 19, Orbulina universa ; 20, Globigerina rubra ; 21, Textilaria globulosa ; 22, Rotalia globulosa ; 22 a,
side-view of Rotalia Boucana ; 23, Grammostomum phyllodes ; 24, Frondicularia annularis ; 25, Triloculina
Josephina ; 26, Nodosaria vulgaris ; 27, Lituola nautiloides ; 28 a, Flabellina rugosa ; 29, Chrysalidina
gradata ; 30 a, Cuneolina pavonia ; 31, Nuuimulites nummularia ; 32 a, b, Fusulina cylindrica.
of the shells are represented much enlarged, excepting the
last three, in Figs. 19 to 32. Many of these animals have
the faculty of extending out, at will, feelers over the body
that are a little root-like, and hence they are called Rhizoporfs,
from the Greek for root-like feet. An enlarged view of one of
LIMESTONE ROCKS OF ORGANIC ORIGIN. 33
the species, with the fibre-like arms extended, is shown in Fig.
33. All of the shells above figured, excepting the last three,
are no larger than the finest grains of sand ; and yet they
contain .a number of cells, each of Fig. 33.
which corresponds to a separate one
of the Rhizopod animals.
Kg. 31 is a large foraminifer
shaped like a coin, and the Latin
for coin, nummus, suggested for it
the name it bears, a Nummulite.
Shells, corals, crinoids, and fora- Eotaiia veneu.
minifers consist almost solely of carbonate of lime, the
material of limestone ; and hence their consolidation makes
limestone. Shells, corals, and crinoids are usually more or
less ground up under the action of the waves or currents
of the ocean, and thus reduced to fragments or sand, before
they are consolidated. Much coral limestone of existing seas
the rock of coral reefs shows no trace of the corals of
which it was made, because all were ground by the aid of the
waves and currents to a coral sand or coral mud before con-
solidation. But in other cases the rock contains fragments of
the corals or crinoids, and sometimes entire specimens. Eig.
34 shows the aspect of a crinoidal limestone when the crinoidal
remains are not wholly ground up; the disks and cylinders
are portions of the stems of the crinoids. The coral reefs
of the Pacific are coral-made limestones, and some of them
2* c
MAKING OF ROCKS.
are hundreds of square miles in area and many hundreds
of feet in thickness.
Foraminifers are so minute that they need no grinding in
order to make a fine-grained
rock. They live in sea-
waters of all depths, and
are especially abundant over
the sea-bottom down to a
depth of twelve or fifteen
thousand feet,, as has been
proved by soundings in the
Atlantic between Ireland
and Newfoundland, and
elsewhere. Chalk is made
mainly of foraminifers, and was of deep-water origin ; and
chalk is now making, and has been through ages past, over
the bottom of the ocean.
There are also some plants, of the order of Sea-weeds, that
secrete lime, and which have thereby contributed to rock-mak-
ing. Among these are included (1) coral-making plants, called
Nullipores, so named from the fact that, while looking like
corals, they have no pores or cells; (2) Corallines, which are
related to Nullipores, but have delicate jointed stems; (3)
CoccolitJiSj which are microscopic calcareous disks, very abun-
dant over some parts of the ocean's bottom and occurring also
in shallower waters.
Crinoidal Limestone.
SILICEOUS ROCKS OF ORGANIC ORIGIN.
35
2. Making of Siliceous Rocks or Masses.
Some of the minutest and simplest of plants and animals
make stony secretions of silica instead of carbonate of lime,
and hence form out of their stony secretions beds of silica
instead of beds of limestone. Although minute, often requir-
ing a high microscopic power even to see them, such species
have thus been large contributors to rock-making through all
geological history. Many of them are remarkable for their
beauty of form and texture.
The plants here included are called Diatoms. Nearly all
are too minute to be distinguished
without a lens. Some of the forms
are shown, . highly magnified, in the
annexed figures, 35-40. They are
strange forms for plants, and still
are known to be of this king-
dom of life. They have lived in
such numbers over the bottoms of
shallow
Figs<
Diatoms highly magnified.
and SeaS, Fig. 35, Pinnularia peregrina, Richmond,
Va. ; 36, Pleurosigma angulatum, id. ; 37,
that the infinitesimal shells have %5^fS^\!SZ
same ; 39, Grammatophora marina, from
SOmetimeS made beds SCOreS Of the salt water at Stonington, Conn. ; 40.
Bacillaria paradoxa, West Point.
yards in thickness. The material
of such beds looks like the finest of chalk. Owing to
the hardness and extreme fineness of the grains, it was used
as a polishing powder long before it was discovered that
each particle was the secretion of a microscopic water-plant.
36
MAKING OF ROCKS.
It is obtained from the bottoms of many marshes, and sold
for polishing; and the packages in the shops from beds in
Maine are labelled Silex. A bed of great extent in Virginia,
Fig. 41.
Richmond Infusorial Earth.
a, Pinnularia peregrina ; 6, c, Odontidium pinnulatum ; d, Grammatophora marina ; e, Spongiolithis appen-
diculata ;f, Melosira sulcata ; g; transverse view, id. ; h, Actinocyclus Ehrenbergii ; z, Coscinodiscus api-
culatus ; j, Triceratium obtusum ; k, Actinoptychus undulatus ; /, Dictyocha crux ; *, Dictyocha ; , frag-
ment of a segment of Actinoptychus senarius ; o, Navicula ; p, fragment of Coscinodiscus gigas.
near Richmond, is in some places thirty feet thick ; and a little
of the dust, under the microscope of Ehrenberg of Berlin,
SILICEOUS ROCKS OE ORGANIC ORIGIN.
37
Figs. 42-44.
who first made known the nature of these polishing powders,,
presented the appearance shown in the foregoing figure.
These forms were all in the field of his microscope at one
time. Nearly every particle is a Diatom or a fragment of
one. Some beds near Monterey, in California, have a thick-
ness exceeding fifty feet.
Among animals making siliceous shells, the following are
examples. (1) A kind illustrated in Pigs. 42-44, related
to the foraminifers, the
animals being Rhizopods,
but differing in their
forms, and in secreting
silica instead of lime.
(2) Most Sponges, for
sponges are animal in na-
ture. Ordinary sponges
are made of horn-like fibres; but in the living state these
fibres are covered thinly with an animal coating which is in
reality a layer of microscopic animals hardly higher in grade
than Rhizopods. In a large part of them these horny fibres
Fig. 45.
Siliceous spicules of Sponges.
are bristled with minute spicules of silica of various forms.
A few of these forms are shown in Figs. 45 a k. Some of
the oblong pieces or fragments in Fig. 41, page 36, are spi-
cules of ancient sponges.
38 MAKING OF ROCKS.
Other sponges consist wholly of fibres of transparent silica,
excepting a thin coating of animal material. One of these sili-
ceous sponges from the bottom of the East India seas is
represented in Pig. 46, but only half the natural size. The
extreme delicacy of the structure might hardly be inferred
from the figure; for the sponge looks as if made of spun
glass, and as if too fragile to be handled. Such siliceous
sponges are common over the bottom of the ocean, and at
various depths below the reach of the waves, whose violence
they could not withstand.
The flint of the world, or hornstone as the most of it is
called (page 4), is nearly pure silica (or quartz), and, like
quartz, it scratches glass easily. It is found imbedded in
limestones and other rocks. It has been made for the most
part out of diatoms and spicules of sponges, and without any
unusual degree of heat. This fact shows that such deposits,
when under water, may be partly dissolved by the cold waters,
and then consolidated without any external aid beyond that
afforded by the saline ingredients of the waters. By the same
means shells and other fossils have often been changed to
quartz, or have undergone a true petrification.
Besides shells, corals, crinoids, forammifers, diatoms, and
sponges, relics of various other kinds of animals are con-
tained in rocks or have contributed to their material. These
are the harder parts of Worms, Insects, Spiders, Centipedes,
and of various Crustaceans (among these last, Shrimps, Crabs,
Fig. 46, Euplectella speciosa, or Glass Sponge.
40 MAKING OF ROCKS.
and inferior kinds) ; the bones and scales of Fishes and Rep-
tiles ; the bones and occasionally the feathers of Birds ; the
bones of Quadrupeds of various kinds, and remains of various
other forms of life ; and, besides, the trades of animals, from
those of Worms and Insects to those of Quadrupeds and Man.
The living species of the globe that have contributed most
to rocks are those of the waters, because rocks are mainly
of aqueous origin ; and chiefly marine species, because the
greater part of rock-making has been performed by the ocean.
Oceanic life is in greatest profusion along the shallow
waters off shore, down to a depth of a hundred feet,
the corals making coral reefs in our present seas not living
at a greater depth than this. But there is abundant life at
greater depths, and even over the ocean's bottom down to
about 15,000 feet. Crabs with good eyes have been obtained
from the sea-bottom at a depth of 5,000 feet; lobsters without
eyes at a depth of 5,000 to 12,000 feet; and a few living mol-
lusks from a depth exceeding 12,000 feet. Besides these species,
there are through all these depths scattered Corals, Crinoids, and
delicate siliceous Sponges related to that figured on page 39.
But Rhizopods are the most abundant species (page 32), and with
them there are the minutest and simplest of plants, Diatoms and
Coccoliths.
3. Making of Peat-beds.
In marshy areas, where spongy mosses of the genus Sphag-
num are growing luxuriantly along with other water-loving
PEAT-BEDS. 41
plants small and large, and some kinds that can stand the
water, but would thrive better were it drier, there are always
deposits of leaves and stems and other remains of plants
forming under the water. The moss, which is the chief plant
in the increasing deposit, has the faculty of dying below
while growing above; and thus its dead stems may be many
yards long, while the living part at top is only six inches
or so. The small plants and shrubs, and the trees, if such
there be, shed their leaves and fruit annually, and these fall
into the water. Annual plants die each year, and their stems
are buried with the leaves. All the plants, the mosses ex-
cepted, sooner or later die, and thus branches and trunks are
added at times to the accumulation in progress. Birds and
quadrupeds may add their bones, and insects, with the vari-
ous inferior kinds of life in such places, may become min-
gled with the other relics.
The materials of plants buried under water undergo a kind
of smothered combustion. They become black, then, below,
are reduced to a pulpy state, or rarely to an imperfect coal;
and the mass thus altered constitutes what is called peat.
Dry woody material consists, one half of carbon, or the
main constituent of charcoal, along with two gases, oxygen
and hydrogen; and in the change the proportion of the gases
to the carbon is diminished about one fifth. The black color
one result of the change is due to the carbon, as in the
case of the black color of soils, many muds, and black clayey
and calcareous rocks.
MAKING OE ROCKS.
The bed of peat sometimes increases until it is scores of
yards in depth. Ireland is noted for its peat swamps ; the
"mosses/' as they are called, of the Shannon, are fifty miles
long and two to three broad. Peat swamps are common
over all continents out of the tropics. The Dismal Swamp
< in North Carolina is a peat swamp from one end to the
other; and no one has yet ascertained the depth of the peat.
The world has had its peat swamps in all ages since the
first existence of abundant terrestrial vegetation; and they
are the sources of all its coal-beds, each coal-bed having
been first a peat-bed. But the kinds of plants concerned
have varied with the successive ages.
2. Quiet Work of Air and Moisture.
When rocks are wholly under water, whether it be salt
or fresh water, they are generally protected from decay. But
if above the water, so that air as well as moisture has
free access, nearly all become altered, and many crumble to
sand or change to clayey earth. Blocks of some kinds of
sandstone that would answer well for under-water structures,
when left exposed to the air for a few years fall to pieces
or peel off in great concentric layers. Crystalline limestone
(white and clouded marble) in many regions covers the sur-
face with marble dust from its decay. Gneiss and nlica
schist are among the durable rocks ; and yet much of the
gneiss and mica schist of the world undergoes slow alter-
QUIET WORK OF AIR AND MOISTURE. 43
ation, so that in some regions they are rotted down or have
become soft earth or a gravel to a depth of fifty or a hun-
dred feet, and even two or three hundred in tropical coun-
tries. This is the amount of decomposition produced in those
places through a very long period of time, perhaps the whole
time from the epoch of their elevation above the ocean.
But it is no measure of the amount that would have taken
place if the decayed portion had been removed as it was
formed, as has often happened; for, in that case, alter-
ation would have proceeded with greater rapidity because of
the freer access of air and moisture.
The granite hills are often thought of as an example of
the everlasting, as far as anything is so on the earth. But,
while there is granite that is an enduring building- stone,
a large part of the granite of the world becomes so changed
on long exposure that the plains and slopes around are
thence deeply covered with the crumbled rock, and great
masses may be shivered to fragments by a stroke of a sledge.
Many granitic elevations over the earth's surface have dis-
appeared beneath their own debris.
Much trap-rock is as firm as the best granite. But other
kinds are rotted down to a depth of many feet or yards, and
sometimes only here and there a ledge shows itself above the
ground as the remains of ranges of hills. Even the most
solid trap, where exposed to the elements, has a decomposed
outer layer, or is weathered, as the change is called. This
44 MAKING OF ROCKS.
crust is often but a line or two deep and has everywhere
the same depth over blocks of like kind. But this depth
is constant,, because, as the elements eat inward, there is as
gradual a loss of the altered grains over the outer surface.
Thus invisible agencies are producing the slow destruc-
tion of the exposed parts of nearly all the rocks of the
globe, even to the tops of the lofty mountains. The firmer
kinds of slates (argyllite), some hard conglomerates and
gneisses, and the compact limestones are the rocks that defy
the elements most successfully.
In this way rocks have been prepared for the rougher
geological work carried on by moving water and ice ; and
through the same means the earth or soil of the world has
to a large extent been made.
This quiet work of air and moisture is really chemical
work ; and it is mostly performed through the chemical
action of two ingredients present in them, carbonic acid
and oxygen. Other agencies aid in this slow destruction, as
explained on pages beyond.
3. The Work of Winds.
Winds, or moving air, carry sands from one place to
another, and wherever the earth's surface is one of dry sand,
and the winds blow strongest and longest in one direction,
great accumulations of sand are made. Even when the win-
dows of a house in a city are ordinarily kept closed, the dust
WORK OF WINDS. 45
will get in. The west winds have driven the sands of the
Desert of Sahara over parts of Egypt, and the ruins of an-
cient cities have thus been buried.
Sea-shores are often regions of sand, owing to the work of
the waves. The heavy winds take up the loose, dry sands and
carry them beyond the beach, to make ranges of sand-hills,
often 20 to 30 or more feet high. Thence the hills frequently
travel inland, through the same means, sometimes burying for-
ests, as on the west coast of Michigan, sometimes overwhelm-
ing villages, as in England and France, leaving at times only
the top of a church-spire to mark the site.
The stratification of a hill of drifted sands is so peculiar
that it is easy to tell when sand-rocks have been formed
through the agency of the winds. Fig. 47 represents a part of
a section observed in the Pictured
Fig. 47.
Hocks on the south shores of Lake
Superior. The layers dip in many
directions. Such a structure is ow-
ing to the accidents to Which the Part of a section of a drift sand-hill,
showing the stratification.
sand-hills are exposed. A heavy
storm perhaps aided by heavy waves at high tide often
carries away part of a hill. Then the winds build it up anew,
putting the successive drifts which make the successive lay-
ers over the new surface, differing much from the first in its
slopes. The hill suffers from another storm, and is again built
up during the period of quieter weather that follows. This
46 MAKING OF ROCKS.
may take place many times. The result is the kind of irregu-
larity of stratification illustrated in the cut.
Sands carried by winds over rocks often wear the surfaces
deeply, as noticed in the Colorado desert, in the Grand Traverse
region near Lake Michigan, and elsewhere. This agency has
scoured out gorges, shaped and undermined bluffs, and worn
away rocks, in the dry parts of the Eocky Mountain region.
Man has taken the hint, and now uses sand driven by steam
to etch on glass and to carve granite and other rocks.
4. The Work of Fresh Waters.
Eunning water is at work universally over a continent
wherever there is a slope to produce movement, and the clouds
yield rain; and it acts with greatest energy where the slope is
greatest, or about high hills and mountains.
The waters of the rains, mist, and dew about the mountain-
tops descend in drops and rills, and then gather into plunging
streamlets and torrents ; the many torrents combine below into
larger streams; and these, from over a wide region, unite to
make the great rivers. The Mississippi has its arms reaching
westward and northward to various summits in the Eocky
Mountains, and eastward to the Appalachians; and its great-
ness is owing to the vast breadth of the area it drains. Not
only mountains, but every small elevation over a land, and
even its little slopes, have, when it rains, their rills combining
into torrents, and these into larger streams, which flow off to
join some river.
WORK OF FRESH WATERS. 47
The waters of the clouds no sooner drop to the ground than
they begin to work, tearing off and carrying away grains of
earth from the rocks or slopes. The stronger rills act in
this way with much greater effect; and the torrents move
stones as well as earth. This work over the larger part of a
country may be almost wholly suspended in the dry season.
But when the rains set in the surface is alive with its work-
ers, small and great. Torrents become increased immensely in
depth and force, and earth and often rocks are torn up and
borne along in vast quantities.
The more rapid the flow of the water the coarser the de-
tritus it can transport; and as a stream slackens its rate the
coarser material falls to the bottom, leaving only the finer to
be carried on. Thus the large stones and then the smaller
will drop as the torrent becomes less and less violent ; but the
earth and gravel may be borne on to the rivers; and these, in
their times of flood, may carry a large part of the burden of
earth to the ocean. Under such a rough-and-tumble move-
ment stones are worn to earth and gravel, and in this pulver-
ized state they may continue the journey seaward. A single
heavy rain-storm has sometimes so filled the narrow gorges of
a mountain that vast deluges of water, rocks, gravel, and trees
have swept down, carrying away houses and spreading desola-
tion over the plains below.
Through the wearing effect of rivers and their tributaries,
reaching to every part of a continent, the mountains, ever
48 MAKING OF ROCKS.
since their first emergence, have been on the move to the
ocean, and we cannot judge of their former height from what
now exists.
The process of erosion is often called, in geology, degra-
dation, because mountains and hills are made low by it; and
denudation, because it removes their exterior.
The average amount of sediment annually carried to the
borders of the Gulf of Mexico by the Mississippi River has
been stated to be 812,500,000,000 pounds, or enough to make
a pyramid a square mile at base over 700 feet in height.
This material is deposited about the mouth of the river, and
is gradually extending it farther and farther into the Gulf.
The fine sediment of rivers settles much more rapidly in salt
water than in fresh, and this is one reason why this material
is prevented from being carried off to the deep ocean.
The great area about the mouth of a large river over which
these deposits are distributed is usually intersected by chan-
nels, and constitutes what is called a delta. Fig. 48 represents
the delta of the Mississippi.
The channel of the river extends far into the Gulf of
Mexico, and terminates in several mouths. The delta stretches
northward nearly to the mouth of Red Eiver, and has an area
of about 12,300 square miles. The waves and currents of the
Gulf act with the currents of the river in the deposition of
the sediment.
The Mississippi is an example of what all rivers are doing,
WORK OF FRESH WATERS.
49
each according to its ability. Some carry their detritus to lakes,
to extend their shores, and aid in filling them. But much of
the detritus is left on the various river-flats, and this part is
called alluvium. Again, a large part reaches the ocean, and
3 i>
50 MAKING OE ROCKS.
is distributed along the borders, making sand-flats, mud-flats,
and ultimately good dry land, to widen the serviceable area
of the continent.
The banks and bottom of a river are generally made of coarser
or finer material, according to its rate of flow in the different
parts. Where it is very slow the bottom and banks are sure
to be of mud, for the very slow movement of the waters gives
a chance for the finest detritus to settle; but if rapid it will
consist of pebbles, if the region contains them. The bank
struck by the current is, in general, more pebbly than the
opposite.
The action of the waters of large lakes in rock-making is
to a great degree the same as that of the ocean.
5. The Work of the Ocean.
The mechanical work of the ocean has been carried forward
chiefly through (1) its tidal movements ; (2) its waves ; and
(3) its currents.
1. Tides. With each incoming tide the waters flow up the
coast and into all bays and mouths of rivers, rising several
feet and sometimes yards above low-tide level; and then, with
the ebb, the same waters flow back and leave once more the
mud-flats and sand-banks of the bays and coasts exposed to
view. This retreat of the tide allows the rivers to discharge
freely and carry out their detritus to sea ; but soon again the
inflow stops the movement outward and reverses it, and dur-
WORK OE THE OCEAN. 51
ing the time of slackened flow the waters drop their detritus,
part about the mouth of the stream, part along the adjoin-
ing coast, and part in the shallow waters of the sea outside.
2. Waves. The sea in its quiet state is rarely without
some swell, which causes at short intervals a gentle movement
on the beach and some rustling of the waters along rocky
shores. Generally there are waves and breakers; and when a
heavy storm is in progress the waves rise to a great height
and plunge violently upon the beach and against all exposed
cliffs, wave following wave in quick succession through days
or it may be weeks together. With each storm the waves
renew their violent strokes, and in many seas the action is
incessant.
* The plunge on the beach grinds the stones against one an-
other, rounding them and finally reducing them to sand, and
the sand to finer sand. The waters after the plunge retreat
down the beach underneath the new incoming wave; and this
" undertow " carries off the finer sand made by the grinding
to drop it in the deeper waters off the coast, leaving the
coarser to constitute the beach.
Thus wave-action grinds to powder and removes the feldspar
and other softer minerals of the sand, and leaves behind the
harder quartz grains; and consequently, wherever there are
beaches of sand, there are offshore deposits of mud made out
of the fine material carried seaward by the undertow. In no
age of the world have sand-beds been formed without the
making of mud-beds somewhere in their vicinity.
52 MAKING OE ROCKS.
The cliffs, or exposed ledges of rock, are worn away under
the incessant battering, and afford new stones and sand for
the beach, and the shallow waters adjoining. Most rocky
shores, especially those of stormy seas, show, by their rugged
cliffs, needles, arches, and rocky islets the effects of the storm-
driven waves.
It is to be remembered that the ocean, as stated on page
42, often finds the work of destruction facilitated by the
weakening or decomposition the rocks have undergone through
the quiet action of air and moisture, and also through other
means explained beyond (page 63).
The waves, as they move toward the shores over the shelv-
ing bottom, bear the sediment in the waters shoreward, and
throw more or less of it on the beach. And thus the beach
grows in extent. The sediment is, in general, either what it
gets from the battered rocks of the coast, or what the rivers
pour into the sea. At the present time the Atlantic receives
an immense amount of detritus through the many large streams
of Eastern North America; and as a consequence the shores
aa-e extensive sand-flats from New York southward, with shal-
low sounds inside ; and the latter are the spaces not yet filled
to the water-level with the deposits of detritus. The coast
has been growing seaward for ages through the same means,
with but little aid from the wear of sea-shore cliffs. But in
the earlier geological ages this was not so; for the continent
was to a large extent more or less submerged, and the waves
WORK OP THE OCEAN. 53
made a free sweep over its surface, battering the rocks in many
places, and thus making its own sediment; for there were only
small streams on the small lands to give any help.
In the warmer seas of the world mollusks are very abundant.
The heavier storm-waves tear them from the muddy bottom
where they were alive, and throw them on the beach. There
they are exposed to the incessant grinding which stones and
ordinary sands experience elsewhere, and thus are reduced to
sand. Every storm adds to the shells of the beach as well
as to the shell-sand. Thus sand-deposits form that are made
out of shells alone; and they keep growing and may become
of great extent. The finer shell-sand is swept out into the
shallow waters, and there produces a finer deposit. The hard-
ening of such deposits makes limestone ; and the shells that
happen to escape the grinding are its fossils. In this way
limestones have been made in all geological ages. Shell rocks
are now forming at St. Augustine, Florida, and the limestone
there made is used as a building-stone.
In other parts of tropical seas there are corals growing
profusely within reach of the waves, or within 100 feet of
the surface. Many are broken or torn up by the waves and
carried to the beach, and there are ground up and spread out
in beach deposits and off-shore deposits. These beds of coral
sand or mud harden, and then become the coral reef rock,
- a true limestone, similar to many of ancient time. South
of Florida, and in other parts of the West Indies, in various
54 MAKING OF ROCKS.
parts of the tropical Pacific, and also in the East Indies and
Red Sea, these coral limestones are now in progress.
3. Currents, The ocean has its system of circulation, or
of great currents. The Gulf Stream is part of it; its waters,
flowing westwardly in the tropical Atlantic, bend northward
as they pass the West India seas, and then pass northeast-
ward, parallel with the North American coast as far as New-
foundland, gradually curving eastward. Thence a part continues
either side of Iceland to the Arctic seas, from which there is
a return, as a cold Labrador current, along the coast of Lab-
rador and farther south. This great current moves but 5
miles an hour when swiftest, and this only in part of the
straits of Florida. Its average rate, parallel with North Amer-
ica, is 2i miles an hour; and it is hardly felt at all anywhere
along the sides of the continent, not even in the Florida
straits. It hence gets no detritus from the wear of coasts,
and is too feeble to carry anything but the very finest silt.
The ocean's bottom shows that it receives almost nothing
either in this way or from the currents of great rivers. When,
however, the continents were submerged a few hundred feet
or less in ancient time, the currents swept over the surface,
and must have done much work in wearing rocks and trans-
porting detritus.
Both waves and gentle currents raise ripples over the sands;
and such ripple-marks, made by the ocean in ancient times,
are often preserved in the rocks (Fig. 49). They show that
WORK OF THE OCEAN.
55
the sands of which the rocks were there formed were within
reach of waves or gentle currents.
The mud of a mud-flat or of a dried-up puddle along a
roadside is often found cracked as a consequence of drying;
and such mud-cracks are frequently preserved in sedimentary
rocks (Fig. 50). They are of great interest to the geologist;
for they show that the layer in which they occur was not of
Figs. 49, 50.
49
Ripple-marks. Mud-cracks.
deep- water origin; but beyond question was exposed, for a
while at least, above the water's surface to the drying air or
sun, as mud is now often exposed along a roadside, or over
the mud-flats of an estuary. Such cracks become filled with
the next deposit of detritus, and this filling has often been
afterward so consolidated as to be harder than the rock out-
side; and hence on a worn surface the fillings of the cracks
56
MAKING OF ROCKS.
Fig. 51.
Rain-drop impressions.
generally make a network of little ridgelets, as in the pre-
ceding figure.
Again, mud-flats sometimes have the surface covered with
rain-drop impressions after a short shower in which the drops
were large; and many shales (rocks made of mud or clay)
retain these markings (Fig.
51) ; others have impressions
of the footprints of animals,
even those of insects.
Such delicate impressions
are preserved, because soon
after they are made they be-
come covered with a layer
of fine detritus; and after that nothing can erase them short
of the removal of the deposit itself.
The rocks that have been made by fresh waters and the
oceans are of vast extent. They are the sandstones, conglom-
erates, and shales of the world; and they include the limestones
also. The ocean has done far the larger part of the rock-mak-
ing. In the earlier geological ages it worked almost alone; for
the lands were very small, and only large lands can have large
rivers and river deposits. Afterward, in the coal-era, there
was at least one large delta or estuary on the borders of the
American continent, that of the St. Lawrence; and ever since
rivers have given important aid. During the last of the ages,
after the continents had reached nearly their present extent,
WORK OF ICE. 57
and the mountains their modern height and numbers, rivers
have done the larger part of the distribution of rock-material.
Sedimentary rocks show that they were formed through the
action of water, often in the rounded or water-worn pebbles
they contain, or the water-worn sand, or from a resemblance
in constitution to a consolidated bed of mud or clay; in their
relics of aquatic life, and the indications of wave-action or cur-
rent-action above pointed out; and in their division into layers,
such as exist in known sediments or deposits from waters.
6. The Work of Ice.
1. Expansion on freezing. When water freezes it expands.
If it freeze in a pitcher, the expansion is pretty sure to break
the pitcher. If it freeze in the crevice of a rock, it opens the
crevice; and by repeating the process winter after winter in the
colder countries of the globe, it pries off and breaks apart rocks,
and makes often a slope of broken blocks, or talus, at the foot
of a bluff. By opening cracks in this w r ay it gives air and
moisture new chances to do their quiet work of destruction.
2. Transportation by the ice of rivers or lakes. When
water freezes over a river it often envelops stones along the
shore ; and then, whenever there is a breaking up, the ice with
its load of stones is often floated off down stream; or if the
water of a stream or lake rises in consequence of a flood, the
stones may be carried farther up the shore and dropped there.
In cold countries ice often forms thickly about the stones
3*
58 MAKING OF ROCKS.
in the bottom of a stream; and as it is lighter than water it
may become thick enough to serve as a float to lift the stone
from the bottom, so that both ice and stone journey together
with the current.
These are commonplace ways in which ice does geological
work. Its greater labors are performed when it is in the
condition of a glacier.
3. Glaciers. Glaciers are broad and deep streams of ice
in the great valleys of snowy mountains like the Alps. The
snows that fall about the summits above the level of perpetual
snow accumulate over the high region until the depth is one
or more hundred feet. At bottom it is packed by the press-
ure and becomes ice. Its weight causes the ice to descend
the slopes of the mountains and along the valleys, which it
fills from side to side. The width of the ice of the valley
may be several miles; its depth in the Alpine valleys is gen-
erally from 200 to 500 feet. '
The glaciers descend far below the line of freezing to where
the fields are green and gardens flourish; and this takes place
because there is so thick a mass of ice. In the Alps the
glaciers stretch down the valleys 4,500 to 5,300 feet below
the snow-line. At Grindelwald two glaciers terminate within
a short distance of the village.
The rate of movement in the Alps in summer is mostly
between 10 and 20 inches a day, and half this in winter; 12
inches a day corresponds to a mile in about 14i years.
WORK OF ICE.
59
Fig. 52 (from a sketch in one of Agassiz's works on glaciers)
represents one of these great ice-streams or glaciers descending
a valley in the Monta E/osa region of the Alps. A valley often
narrows and widens at intervals, and changes its slope at times
Fig. 52.
Glacier of Zermatt, or the Corner Glacier.
from a precipitous to a horizontal surface. The ice has to ac-
commodate itself to all these variations. On turning an angle
it is broken, or has great numbers of deep <f crevasses " made
through it, especially on the side opposite the angle. On com-
60
MAKING OF ROCKS.
mencing a rapid descent, great breaks, or crevasses, cross the
glacier from one side to the other. On reaching a level place
again the ice closes up, and the glacier loses nearly all its
crevasses. The ice is brittle, and freezes together when the
separated parts are brought in contact again; so that, as it
moves, it goes on breaking and mending itself. Ice is plastic ;
for it may be made into rods by pressing it through a hole,
and will take the impress of a medal ; so that it can accommo-
date itself in this way also to the changing character of the
surface over which it moves.
Along the sides of the glacier the cliffs of rock often send
down stones and earth, or avalanches of ice and rocks; and
these make a line of earth and rocks along either margin, which
Fig. 53.
Glacial scratches and planing.
is called a moraine. These moraines are carried with the ice
to where it melts, and there dropped. Other blocks are taken
up by the sides and bottom of the glacier.
WORK or ICE.
61
Wherever a glacier has moved the rocks are scratched,
planed, or polished, often with great perfection, as illustrated
in Fig. 53.
Fijr. 54.
View on Roche-Moutonn^e Creek, Colorado.
Ledges of rocks also are rounded, making what are called
sheep-backs, or, in French, roches moutonnees. Fig. 54 repre-
sents the roches moutonnees in a valley of the mountains of
Colorado, a valley leading up to the Mountain of the Holy
Cross, seen in the distant part of the view. It is from the
Beport of Dr. Hay den for 1873. No glaciers exist there
now; but once they were of great extent and depth. The
62 MAKING OF ROCKS.
scratching and polishing are done by the stones in the bottom
and sides of the glacier; and these stones, as is natural, are
also planed off and scratched.
4, Icebergs, In the Arctic regions the glaciers of Green-
land, loaded with their moraines, extend down into the sea,
and the part in the water sooner or later breaks off and floats
away as an iceberg. These icebergs are carried south by the
Labrador current, and large numbers of them in the course of
a season reach the Banks of Newfoundland. There* they find
the waters warmer, in consequence of the nearness of the Gulf
Stream, and they melt and drop their burden of stones and
earth into the waters. It has been suggested that the Banks
of Newfoundland owe their existence to the melting and con-
sequent unlading there of icebergs.
It thus appears that ice does geological work (1), in the act
of formation, through its expansion ; as glaciers, (2) by trans-
porting over the land earth and stones and rocks, some of the
rocks as large as ordinary-sized houses, and dropping them
when the ice melts; (3) by tearing apart rocks through its
movement wherever there are opened seams into which it can
pass ; (4) by wearing deeply into the soft rocks over which it
may move, and scratching and polishing hard rocks; and, as
floating ice or icebergs, by transporting rocks, stones, and earth
from one region to another; and (5) it often makes temporary
dams across valleys, that cause great devastation when they
give way.
WORK OF HEAT. 63
7. The Work of Heat in Rock-making.
The effects here mentioned are the following :
1. Expansion and contraction from change of temperature.
2. The fusion of rocks, and their ejection through volcanic
vents and fissures.
3. Solidification and crystallization of fragmental rocks,
through long-continued heat, and the filling of fissures and
making of veins.
1. Through Expansion and Contraction.
Owing to the alternation each day of sunlight and darkness,
the surfaces of exposed rocks experience an alternate heating
and cooling, and therefore alternate expansion and contraction.
This cause, which is sufficient to break the solder of soldered
metallic roofs on houses, to loosen the cemented blocks of a
stone wall, and to give a perceptible movement to high stone
towers, tends to start off the grains, and sometimes separates
an outer layer from bare rocks, especially when the surface is
weathered. As it is in action over the whole surface of the
earth, it is an important addition, in a quiet way, to the
chemical work of air and moisture, in the making of earth or
gravel for the formation of rock deposits; and it has been so
ever since the sun first shone upon bare rocks. A foot or two
of soil is a protection against this method of degradation.
Heat gaining access to rocks beneath a region expands
MAKING OF ROCKS.
them and causes an elevation of the surface; and loss of heat
produces a reverse effect. Fractures may attend such changes
of level, and also light earthquakes.
2. Making of Rocks through Fusion: Volcanoes.
L Volcanoes. Igneous rocks, or those made by the cooling
of melted rock-material, are described on page 18 as having
Fig. 65.
Mount Shasta, from the north : from a photograph by Watklns.
come to the earth's surface from below through fissures 5 and
also as sometimes having been ejected at intervals from one
and the same opening for long periods of time.
WORK OF HEAT. 65
When fissures are filled and closed by one eruption, they
make dikes of igneous rock, and also one or more beds if
the melted material flows from the fissure over the region
adjoining.
But when a vent remains open for many successive eruptions
it becomes then the centre of a true volcano or fire-mountain.
The outflows of liquid rock, and ejections of volcanic sand or
cinders from one side and the other around the vent, produce
a hill or mountain of a form more or less nearly conical.
Fig. 55 represents Mount Shasta, one of the volcanic mountains
of Western North America, having an elevation, according to
Whitney, of 14,440 feet. It is not now in action, yet has
hot springs near its summit. It also represents well the gen-
eral form of the great volcanoes of the Cascade range to the
north of it in Oregon, and of those along the Andes in South
America. Of the latter Cotopaxi is an active volcano 19,660
feet in height, and Arequipa another, 18,877 feet, while Acon-
cagua, of Chili, has a height of 22,478 feet, and is the loftiest
peak in the Andes.
Active volcanoes send forth only vapors in their times of
quiet. In periods of eruption streams of lava (or liquid rock)
are poured out, either over the edge of the crater or
through breaks in the sides of the mountain. The latter is
the common mode. At the same time cinders or fragments
of lava are often thrown from the crater to a great height
above the volcano, to fall in showers around.
66 MAKING OF ROCKS.
Volcanoes vary much in angle of slope. When made of
cinders the angle is often 40 to 42. If formed through the
alternations of lavas and cinders, or of tufas, the slope may be
30 or less, as in Figs. 55 and 56. Fig. 56 gives the slopes of
rig. 56. the volcano of Jorullo, in Mexico. Many
of the grandest volcanoes of the world,
^^ like Etna, and those of Hawaii, in the
Sandwich Islands, have an exceedingly gentle slope, the
height only a twentieth of the breadth, as in Fig. 57, giving
the slope of Mount Loa, of Hawaii. These last are made
almost solely of lavas; and they have so gentle a slope, be-
cause the melted rock of the region flows off freely.
The eruptions of volcanoes are owing mainly to the waters
that gain access to the fires. The rains of the region produce
Fig. 57.
underground streams that descend and pass into the melted
rock, there to be changed to vapor ; and sea- water, when vol-
canoes are near or in the ocean, presses its way in, or gains
access suddenly through fractures. The vapor penetrating the
liquid mass expands the whole, causing it to rise in the vent.
The fires become hotter with the increasing height of the col-
umn of melted rock in the mountain, and the vapors more
active. The pressure from the high liquid column, and from
the vapors, breaks the mountain, and the lavas run out, devas-
WORK OP HEAT. 67
tating the country, it may be, for a score of miles or more.
When the sea gains sudden access to a volcanic vent, the erup-
tion is accompanied with violent quakings of the mountain.
Every few years the country on one side or another of Yesuvius
is deluged with the fiery rock, cultivated fields buried, and not
unfrequently villages destroyed. Pompeii and Herculaneum
were buried beneath the cinders of an eruption that took place
in the year 79 of our era; and since then several streams of
lava have flowed down over Herculaneum, adding to the depth
of rock over it. The deposits of cinders make a kind of soft
sandstone called tufa.
Mount Loa, on Hawaii, has had six great eruptions througli
fissures in the sides of the mountain within 30 years. There
is a summit crater (L on the map) at a height of 13,760 feet,
and another called Kilauea (at P), nearly 4,000 feet above the
sea, which is the larger of the two. The map shows at 1, 2,
3, 4, 5, and between P and K, the courses of the eruptions.
K is the position of another volcanic mountain, Mount Kea,
as high as Loa, and H, of another, 10,000 feet high.
The liquid rock comes up from some deep-seated fire-region.
Yolcanic mountains are very numerous along the Andes;
in Central America and Mexico; in Oregon and Washington
Territory, from Mount Shasta to Mount Baker and beyond; in
the Alaska archipelago on the north; all along the west side
of the Pacific through Japan and the East Indies ; southward
in the New Hebrides, New Zealand, and in Antarctic regions.
68
MAKING OF ROCKS.
Thus the Pacific, the great ocean of the globe, is girt with
volcanoes, besides having many over its surface. The Atlantic,
in contrast with it, has none on its borders, except in the Gulf
Fig. 58.
Island of Hawaii.
L, Mount Loa ; K, Mount Kea ; H, Mount Hualalai ; P, Kilauea or Lua-Pdle" ; i, Eruption of 1843 ; 2 . of
1852 : 3, of 1855 ; 4, of 1859 ; a, Waimea ; b, Kawaihae ; c, Wainanalii ; d, Kailua ; e, Kealakekua ; f,
Kaulanamauna ; g, Kailiki ; h, Waiohinu ; i, Honuapo ; J, Kapoho ; k, Nanawale ; /, Waipio ; m, first
appearance of eruption of 1868 ; n, Kahuku. The courses of the currents i, 2, 3, and 5 are from a map by
T. Coan, and 4, from one by A. F. Judd.
of Guinea on the coast of Africa, and in the West Indies;
and but few over its interior.
Hot springs often make deposits of silica around them,
owing to the silica the heat has enabled the waters to take
up from the rocks with which they are in contact. Such
WORK OF HEAT.
69
Fig. 59.
Beehive Geyser in action.
springs sometimes throw their waters in jets at longer or
70 MAKING OF ROCKS.
shorter intervals,, and they are then called geysers. One of
the geysers of the Yellowstone Park, in the Rocky Mountains
(where there are great numbers of them), is represented in ac-
tion in Pig. 59, taken from Hayden's Report for 1873. It
throws the water to a height of 200 feet or more. The gey-
sers of Yellowstone Park are mostly about the Pire-hole River,
a fork of Madison River, and near Shoshone Lake, the head of
Snake River, and not far from the head of the Yellowstone.
The number of hot springs, hot lakes, and geysers in the Park
has been stated to be not less than 10,000.
Solfataras are regions about volcanoes where vapors issue
and sulphur is deposited. The name is from the Italian for
sulphur.
3. Solidification, Metamorphism, and Formation of Veins.
1. Solidification. Limestones have been solidified through
carbonate of lime (bicarbonate) in solution in waters; also
some sandstones by the same means, the lime-salt being de-
rived from the grains of shells, corals, etc., in these rocks.
Some sandstones have been partially hardened by the silica in
solution in many cold waters, especially where there are diatoms
(page 35) in the rock, to enter into solution. The masses of flint
and hornstone in rocks are made out of diatoms and other sili-
ceous relics (page 38) by consolidation in cold waters; and many
fossils have been turned to quartz (silica) in the same way.
But some of the oldest of sandstones and shales are still
WORK OF HEAT. 71
soft or unconsolidated. A large part of the more solid have
had the aid of heat in solidification, heat producing siliceous
waters for the work. Hot waters containing in solution some
alkali, as soda or potash, have the power of dissolving silica;
and they find both the silica and the needed alkali in the
feldspar of igneous or other rocks, and hence the waters of
hot springs are generally siliceous.
2. Metamorphism. This heat, when it has been long con-
tinued, probably for thousands of years, has not only con-
solidated the rocks, but has also crystallized them, turning
sandstones, shales, and conglomerates into the metamorphic
rocks, granite, gneiss, mica schist, hornblende rock, and
other kinds. Those fragmental rocks were made by the pul-
verizing of granite, gneiss, mica schist, and the related rocks;
and hence the return to granite, gneiss, mica schist, and the
like by a new crystallization, when acted upon throughout by
heat and moisture, is not a matter of surprise.
Moisture at a high temperature has, moreover, great decom-
posing and recomposing power ; and many minerals as mica,
feldspar, hornblende, and others may be made and crystal-
lized through its action, and thus become constituents of met-
amorphic deposits when not originally present. The heat of
metamorphism was generally much below that of fusion, this
being obvious from the fact that the stratification of the rocks
is perfectly retained; for the layers of mica schist and gneiss
correspond with the bedding of the sandstone or shale out of
72 MAKING OF ROCKS.
which they were made. But, in some cases, the heat was suffi-
cient to soften the rock, and then the planes of stratification
were obliterated, making granite instead of gneiss, granite
differing from gneiss only in the absence of anything like strat-
ification or an arrangement of the material in layers. There
are all shades of gradation between granite and gneiss.
Heat has changed common or compact limestones, that
were gray to black in color and full of fossils, into white or
clouded crystalline limestones, that is, white or clouded mar-
bles. In a case of this kind the metamorphism may have con-
sisted simply in crystallization. Yet at the- same time the
impurities of the limestone have sometimes been converted by
the process into grains of mica and other minerals, which are
distributed through the rock. Similarly other rocks, like mica
schist, gneiss, etc., have been filled with various crystallized
minerals, as garnet, tourmaline, staurolite; and even the gems,
sapphire, ruby, topaz, and the diamond are among the results
of the metamorphic process. Moreover, beds of earthy iron-
ores have been made into crystalline iron-ores, examples of
which on a grand scale occur in the Adirondack region of
Northern New York, the Marquette region in Michigan, and
in the Iron Mountains of Missouri.
Metamorphism has been carried on at once over regions
thousands of square miles in area. The rocks undergoing the
change were undergoing also an upturning and fracturing on
a scale as extensive j and the movements were the source of
WORK OF HEAT. 73
the heat that caused the metamorphism, just as the rubbing
of two sticks together produces heat. The upturned ore-beds
often look like veins of ore, and are sometimes wrongly so
called.
Hot springs occasionally produce metamorphism in the rocks
about them, besides causing ordinary consolidation. The
waters of geysers (page 68) deposit a large amount of silica
ill the form of opal, making opal basins for themselves to
play in, and spreading the opal widely over the region around.
They also produce the petrifaction of wood, changing the trunk
of a tree into silica, and generally without obliterating the
grain or structure of the wood. But the making of such
petrifactions does not demand heat, as they have often been
produced in beds of earthy or calcareous mud when siliceous
infusoria were abundant in it, as stated on page 70.
The opal of geyser regions is of a coarse kind, yet is often
beautiful in its forms about the pools. The precious opal has
been mostly produced in feldspathic lavas (trachytes) that have
been long subjected to hot waters, and which, under the ac-
tion, have yielded up part of their silica to deposit it again
as opal in the cavities of the rock.
3. Veins, Rocks have often been extensively broken so as
to be intersected by great numbers of fissures large and small;
and in upturnings the layers, especially of shaly rocks, have
been opened, as the leaves of a quire of paper are separated
more or less on bending it into an arch. The fissures, in
4
MAKING OF ROCKS.
such cases, and all the openings, have become filled while met-
amorphic changes were in progress, by crystallized rock-mate-
rial, derived from the rock either side of the fracture or from
depths below ; and metallic ores of various kinds, as of lead,
silver, and copper, and also native gold, have often been car-
ried into the openings or fissures along with the rock-material.
Veins (Figs. 60, 61) are the fillings of fissures, and this is the
most common way in which they have been made. The mate-
Figs. 60, 61
Rocks Intersected by veins, a. b.
rial is carried in, from the rocks on either side or below, by the
moisture present, this, at the high temperature, dissolving it ;
and thus laden it has pressed into all opened spaces, there
to deposit it as long as there was open space to be filled.
Such veins, and the seams occupying openings between layers,
afford a large part of the metals of the world, iron excluded.
Gold is found in such veins, or else in the gravel made out
of gold-bearing rocks by some process of wear or destruction.
Many veins consist of quartz alone (such are most gold-
bearing veins) ; others of coarse granite, and of various other
MAKING OF VEINS. 75
kinds of rock-material. They are frequently banded, that is,
are made up of layers parallel to the walls. These layers
consist of different kinds of minerals and ores : there may be
an outer layer of quartz; next one of ore; then another of
quartz, or of calcite, or of some other earthy mineral; then
perhaps another of ore. Such a structure is proof that the
vein was filled by deposition against the walls, one layer after
another, and that they were not made by injection of liquid
rock from below.
Other metallic veins have been made in connection with
igneous ejections. Fissures have opened down to regions of
liquid rock, and sometimes ores have ascended along with the
liquid rock; but often, in some part of the same disturbed
region, other fissures have opened which have received from
below only vapors or solutions of mineral matter including the
ores. The waters that exist as subterranean streams, especially
beneath stratified rocks, have frequently made their way into
such opened fissures, and there becoming at once highly
heated, have aided in carrying the material upward, and also
in determining its condition and its arrangement in the veins.
In Fig. 61 the vein a is broken off and displaced that
is, faulted along the line of the vein 6. When the fissure
occupied by the vein b was opened the rock of one side
slipped by, or was shoved by, that of the other side, and so
the fault or displacement was made. Such faults are very
common.
76 MAKING OF VALLEYS.
II. Making of Valleys.
VALLEYS are made (1) by erosion by the streams of the
land, the common way ; (2) by uptif tings or flexures of
rocks making mountains and leaving troughs or low regions
between the mountains as valleys ; (3) through fractures of
the earth's crust.
L Valleys of erosion. Slopes of sand or gravel are some-
times deeply gullied by the heavy rains of a single day, or,
in geological language, deeply eroded, or eaten out as this
word means. This work of the rains often gives a very exact
model, on a small scale, of the valleys and ridges of moun-
tain regions. The gully, or little valley, has often (1) a preci-
pice at its head; (2) little waterfalls along the steep part of
its course, wherever there was a harder layer of sand; (3) a
narrow bottom with steeply sloped sides; but, near the foot
of the hill, where the surface is nearly horizontal, a broad and
flat bottom of sand laid down by the spreading waters. And
the ridgelets between the little valleys have often a broken,
knife-edge summit in their upper part, and are broader below.
The reader should study carefully the first gullied slope of
this kind that he may meet with, for it will be a study of
valley-making over the world. Only a single night's rain may
have sufficed to make the little valleys and ridgelets of the
sand slope, because the sand was not firmly consolidated. But
MAKING OF VALLEYS. 77
if the rocks be ever so hard they yield in the same way, and
with time enough, the same forms, on the scale of the grand-
est mountain region of the world, have resulted. Many of
the river-valleys of North America, and of other continents,
illustrate this action of running water. Watkin's Glen, near
Ithaca, Trenton and Niagara Falls, in Central and Western
New York, and the Valley of the Upper Mississippi, afford
examples.
The character of the valleys and ridges will depend much
on the hardness, structure, and position of the rocks. "When
the beds are nearly horizontal, precipices and waterfalls are
most common.
The Colorado Eiver of Western North America runs for two
hundred miles through a gorge or caiion with vertical walls of
rock in many places over 3,000 feet high. The sketch in Fig.
62, from a photograph obtained by Powell's expedition, is a view
of a portion of this canon between the Paria and the mouth
of Little Colorado, called Marble caiion. The walls in the dis-
tant part of the view have a height of 3,500 feet, and consist
of limestone, whence its name. But in other parts of the Col-
orado canon there are various kinds of strata, and in some
places the cut has been made deep into the underlying granite,
and all is the work of the river. The waters have a rapid
and often plunging flow, owing to the slope, and carry along
pebbles and stones, and these stones aid greatly in the erosion.
But to wear out so wide and deep a channel a long period of
78
MAKING OE VALLEYS.
Fig. 62.
Marble Canon, on the Colorado.
time was required. Above the gorge, some miles back from the
river, the horizontal rocks are piled up to a still greater height,
reaching in some places a level 8,500 feet above that of the
bed of the stream ; and these piles of strata standing in sep-
arate ridges, sometimes in the form of pinnacles, castellated
structures, and table-topped mountains, are parts of great rock-
formations that once spread across the wide region. They
show that erosion has carried away the larger portion of these
upper rocks, the mountains and pinnacles being merely rem-
nants of them.
MAKING OF VALLEYS. 79
The ocean may have aided in the removal when the land
stood at a lower level, partly submerged; but it could not
have cut out the gorge or canon ; for the work of the ocean
is to wear off headlands, form sand-flats or beaches along
coasts, and fill up bays, not to cut channels into a coast
and make deep valleys. The ocean has done but little valley-
making, and only that of the broadest kind, when its wide
currents swept over the submerged continent. The gorging of
mountains and plains it has left to the running waters of the
land. These running waters have been aided in some cases
by glacier-ice (page 58).
2. Valleys made by the upheaval of mountains. The wide
Mississippi valley is a depression between the Eocky Moun-
tains on the west and the Appalachians on the east. The
making of these mountains was the making of the valley.
The Connecticut and Hudson Eivers occupy depressions that
were probably made by uplifts either side of them. The Adi-
rondacks are among the oldest of mountains. Long after
these the Green Mountains were made; and when raised, the
valley in which lies Lake Champlain ,was a region left low at
the time. Again, the valley of the Sacramento originated in
the making of the Sierra Nevada on one side, and, later, the
Coast ranges on the other.. The other continents afford simi-
lar examples.
8. Valleys made by fractures of the earth's crust 1. A
great fissure in a volcanic mountain opened for the ejection
80 MAKING OF MOUNTAINS,
of lavas has sometimes been left, after the eruption ceased, as
a deep valley. 2. Great regions have subsided in consequence
of subterranean movements, leaving valley-like depressions.
3. Profound fractures have taken place in connection with
mountain-making, leaving sometimes open rents, as narrow
valleys or gorges.
But, notwithstanding the frequency of fractures, there are
few valleys over the earth that can be pointed to as made in
this way. Fractures have sometimes determined the courses
of streams ; but the stream, thus guided in its original course,
has afterward carried forward its work of erosion, and made
the great valley in which it flows.
III. Making of Hills and Mountains, and the
attendant effects.
THERE are three prominent methods of mountain-making,
producing widely different results.
I. Mountains made by Igneous Ejections.
Mountains have been made by igneous ejections, especially
by those of volcanic vents, as explained on page 64. Thou-
sands of square miles over the western slope of the Rocky
Mountains have been covered by igneous rocks, and in Oregon
they have a thickness of more than 4,000 feet; and, besides,
they form cones there, whose summits are 10,000 to 14,440
AND ATTENDANT EFFECTS. 81
feet above the sea. The loftiest peak of the Andes, nearly
23,000 feet high, as already stated, and numerous others hi that
chain, were made by volcanic action. Mount Etna, in Sicily, is
nearly 11,000 feet high; two volcanic mountains of Hawaii
are nearly 14,000 feet high, and another is about 10,000.
This is the least important of the methods by which moun-
tains have been formed.
2. Mountains and Hills produced by the Erosion of
Elevated Lands.
In all mountain regions the lofty summits and ridges have
been shaped out mainly, as already explained, by running water,
and such heights are therefore examples of the results of ero-
sion on elevated lands. But the mountain-making is a little
more completely the work of erosion when a region of hori-
zontal rocks, which when first raised was a lofty plateau, has
undergone long erosion. Owing to the height, perhaps several
thousand feet, the torrents which the rains make and feed have
a steep descent, and therefore great eroding power; and ulti-
mately such a plateau has often been reduced to a region
of profound valleys and precipitous ridges. The elevations
described on page 78, as the remnants of a great rock-forma-
tion, are examples of mountain sculpture of this kind. These
remains are battlemented heights, temples of mountain-dimen-
sions, towers, and columns. The elevations have often a broad
cap of harder rock at top, and if of much breadth they are
4* F
82
MAKING OE MOUNTAINS,
Fig. 63.
called mesas, from the Spanish mesa, a table. The Catskills
are a group of high summits 3,000 to 4,000 feet above the
sea-level, carved by running water out of an elevated region
of nearly horizontal rocks. Such examples are very common
over the world. For in the changes of level which the earth's
crust has undergone areas have often been lifted without much
disturbance of the beds.
Examples of monumental
forms on a small scale oc-
cur in Colorado, and have
given the name of Monu-
ment Park to the region.
Pig. 63 is a sketch of a
scene in it, from Hayden's
Eeport for 1873. Such
effects of erosion may have
been produced mainly by
rains and running water ;
but they are in part due
to the winds j to the quiet
work, chemical in nature, of air and moisture; to the alter-
nate heating and cooling of the surface in consequence of the
daily changes of temperature; and, in frosty regions, or where
the winters are cold, to the freezing of moisture over the
surface.
Over undisturbed regions of Tertiary and Quaternary for-
Erosion in Monument Park, Colorado.
AND ATTENDANT EFFECTS. 83
mations erosion has often reduced the once level surface to a
collection of hills. In some parts of the eastern slope and
summit of the Rocky Mountain region the Tertiary is worn
into a labyrinth of valleys and variously shaped ridges, needles,
and table-like elevations.
This mountain-making by erosion is an external sculpturing
of the earth's surface, and not true mountain-making, the
subject considered under the third head.
3. Mountains made by Upturnings and Flexures of Rocks,
and Bendings of the Earth's Crust.
Mountain ranges have been made, for the most part, through
bendings of the earth's crust, and the upturning and flexures
of the rocks.
1. Upturned rocks. The layers of stratified rocks were, with
small exceptions, originally horizontal, this being the position
which layers of sediment usually have when forming. They
are now very commonly more or less upturned. Sometimes the
angle of inclination is small; but in most mountain regions
the beds are inclined at high angles, and often are vertical or
nearly so. In the study of the inclined positions of strata the
geologist studies the origin of mountains.
The inclination of the beds below a horizontal plane is called
the dip; and the horizontal direction at right angles to the
dip is the strike. When the roof of a house slopes in oppo-
site directions from a horizontal ridge-pole, the angle of slope
MAKING OF MOUNTAINS,
or pitch of the roof corresponds to the dip j and the direction
of the ridge-pole, to the strike.
Some of the positions of upturned rocks are shown in the
following figures. Fig. 64 represents a ledge of rocks pro-
Figs. 64, 65.
65
Upturned strata.
jecting above the ground; d p is the direction of the dip,
and s t that of the strike. Fig. 65 represents a portion of
the coal-formation with stumps of trees rising out of the coal-
beds, which have lost their vertical position because of the
upturning of the strata.
Figs. 66-70.
66
Flexed or folded strata.
2, Flexures. Pigs. 66-70 represent flexures or folds of
the strata, such as are of common occurrence. The folds
AND ATTENDANT EFFECTS. 85
in a mountain region are sometimes many miles in span, and
often one arch rises beyond another. The Appalachians and
Jura Mountains are full of examples. The upward bend (at
a x in Figs. 66 69) is called an anticlinal, from the Greek
signifying inclined in opposite directions ; and the downward
bend (at a x) a synclinal, meaning inclined together, a x,
a x' are the positions of the axes or axial planes of the folds,
a x an anticlinal axis and a' x' a synclinal axis. In Figs.
68, 69 the folds are pressed over beyond a vertical, so that
the axial plane makes a large angle with a vertical line. In
Fig. 70 three folds are raised together.
Fig. 71.
ffl
Section from the Great North to the Little North Mountain, through Bore Springs.
1 1, positions of thermal springs.
Fig. 71 represents an actual section six miles long, from a
part of the Appalachians illustrating well the flexures. But
it illustrates another fact: that, since the flexures were made,
the region has been worn by waters, either those of rivers or
the ocean, so that the tops of the flexures are worn off, and
where they once were^ there are now valleys; such a valley
is represented in Fig. 71, to the left of the middle above
II. The tops of such folds would have been broken deeply
while the bending was in progress, and the breaks would have
opened upward; and therefore these should be the parts most
deeply eroded. The thin black layer over IV, on the left,
MAKING OE MOUNTAINS,
was once continuous with IV, near the middle of the section;
and so with the rest. To the right end of the section the
beds are vertical.
Another view of upturned and eroded rocks as they occur
at a locality in Western Colorado is given in Eig. 72. The
Fig. 72.
Upturned strata of the west dope of the Elk Mountains, Colorado.
The light-shaded stratum, Triassico-Jurassic ; that to the right of it, Carboniferous ; that to the left,
Cretaceous.
strata in the foreground have the reverse dip of those more
distant, showing a twist connected with the upturning.
Other examples of folding and of subsequent degradation,
from the Alleghanies, are illustrated in Pigs. 73-78. In
Figs. 78 - 78.
75
Degradation of a folded mountain region.
each case the harder stratum in the series determines in a
large degree the final form of the hill and the landscape effect
of the erosion.
Fig. 79 represents a still more remarkable case of flexures
AND ATTENDANT EFFECTS.
87
and subsequent erosion; the folded region lias been worn away
to a nearly level surface, so that the existence of flexures is
to be ascertained only in vertical sections of the rocks. Ee-
gions of such folded rocks are generally very difficult to study,
because of the extensive erosion. Ledges and ridges in which
the strata slope only in one direction are often one side or
part of a great fold.
Fig. 79.
General view of folds in the Archaean rocks of Canada.
3. Fractures and Faults, Besides flexures, great and small
fractures have been made during epochs of upturning or
mountain-making. Fig. 80 represents strata thus broken; and,
moreover, the beds are displaced along the fractures. The
beds numbered 1, 1, 1 were once a single continuous layer;
Figs. 80, 81.
Fractures and Faults.
and so with the others ; but at the time of fracture there was
a dropping of the middle portion, so that along each fracture
there is now a fault, or displacement. Another case is illus-
88
MAKING OE MOUNTAINS,
trated in Fig. 81. The fault in a vein described on page 75
is another example. The figures represent faults or displace-
ments of only a few feet or yards; but in many faults, pro-
duced in the making of a range of mountains,, the rocks of
one side of a fracture have been pushed up, or have dropped
down, thousands of feet. When fractures are very numerous
over a region, and of great extent and regularity, they are
called joints.
4 Unconformable strata. 'Rocks are often laid down hori-
zontally over upturned rocks; the layers of the two do not
then conform to one another; as in Pig. 82, in which the
Fig. 82.
Section from south side of the St. Lawrence. Canada, between Cascade Point and St. Louis Rapids.
i, gneiss ; z, Potsdam sandstone.
rocks 1 and 2 are unconformable, while 2 and those overlying
2 are conformable. In the figure there is a fault represented
to the left of the middle; and there are others farther to
the left, which are confined to the lower beds (1), and which,
therefore, were made before the next stratum above (2) was
deposited.
5. Earthquakes. The upturning, flexing, and fracturing of
rocks could not have taken place on so grand a scale without
sudden shakings or jars of the rocky strata; and every such
jar was an earthquake. A scratch of a pin on the end of a
AND ATTENDANT EFFECTS. 89
log may be heard by placing the ear at the other end, be-
cause the vibration made by the scratch travels along the log,
and with great rapidity. A jar in the earth's crust or its
rocks travels in the same way. It has often, in modern times,
been felt through a hemisphere. Subterranean thunder has
been a consequence of it ; and profound fractures of the earth's
surface, resulting sometimes in the destruction of cities and
human lives. Earthquakes occur whenever there is any yield-
ing or slipping or fracture of the rocks beneath the earth's
surface; and they are most likely to occur along the moun-
tain border of a continent where have been the greatest up-
turnings, and especially where there are volcanoes along such
borders.
6. Metamorphism. The upturning, fracturing, and flexing
attending mountain-making accounts for the heat required for
metamorphism, and for the very wide extent of most areas of
metamorphic change; for regions of metamorphism are regions
of upturned rocks (page 72).
7, Cause of upliftings, fractures, and flexures, and of mountain-
making. If a quire of paper, lying on a table, be pressed
together at the front and back edges, it will rise into a
fold ; and, in case the paper is a soft and inelastic kind, into
a series of folds. Pushing from below will make it bulge up-
ward, but only lateral pressure will make a succession of
folds. The facts with regard to flexures in the rocks of moun-
tain regions prove that the force which has made the great
90 MAKING OF MOUNTAINS,
series of folds, uplifts, and fractures has acted laterally ; that
is, it was lateral pressure within the earth 's crust.
Mountain ranges occur on all the continents, showing that
the cause of uplift and flexure has been a universal one; and
so lateral pressure within the earth's crust is a force neces-
sarily universal in its action. Mountain ranges are hundreds
and even thousands of miles in length; and a cause thus
universal is sufficient to have made all, whatever their length
or height.
This lateral pressure is attributed to the admitted fact
that the earth was once melted throughout, and has gradually
cooled over its surface ; and that the first crust formed
has been thickening below from the continued cooling. In
cooling from fusion a rock contracts, losing on an average
a twelfth of its bulk ; and hence continued cooling means
continued contraction beneath the first-formed crust; and an
effort to draw it downward. The crust would be necessa-
rily put, under such circumstances, into a state of pressure
of every part against every adjoining part, like the pressure
between the stones of an arch ; and if any part gave way, or
the crust were flexible at all, there would be uplifts, flexures,
breaks, or faults. The flexures in the earth's strata are, then,
the effects of this lateral pressure, and are some evidence
as to its extent and power.
The great ranges of mountains are situated, for the most
part, on the borders of the oceans. Thus on the Atlantic
AND ATTENDANT EFFECTS. 91
border there is the Appalachian chain, while on the Pacific
stand the lofty Bocky Mountains. Again, in South America
there are the Brazilian Mountains on the east, and the far
greater chain of the Andes on the west. Other continents
illustrate the same truth, that the continents have high
borders and a low interior, and also that the highest border
faces the larger ocean.
Moreover, the volcanoes of the continents are, with few
exceptions, near the ocean, and far the greater part of them
are on the borders of the Pacific or larger ocean (page 67).
These facts prove that the breaks and uplifts that were
made by lateral pressure in the earth's crust were mostly
confined to the borders of the oceans, and that they were
most extensive on the sides of the largest ocean.
A reason for this position of the great mountain chains
near the oceans is found in the fact that the crust of the
earth that lies beneath the ocean's bed is lower in level than
that of the land, and the basin-like depression has rather
abrupt sides toward the continents. Owing to this the action
of the lateral pressure from the direction of the ocean was
obliquely upward against the land, and therefore just what was
required to push up the borders of the continents into moun-
tains, or to produce flexure after flexure in the yielding rocks,
or to break them and give outflow to floods of lava.
Mountain chains are the result of more than one moun-
tain-making process. A single example will suffice to illus-
92 MAKING OF MOUNTAINS.
trate this truth. The range of elevated land from Labrador
to Alabama is called the Appalachian chain. But the Adi-
rondacks, the Highlands of New Jersey, and portions of the
Blue Eidge of Pennsylvania and Virginia were made long
before the rest. The Green Mountains east of the Adiron-
dacks were next raised; then, after another immense period
of time had passed, at the close of the Carboniferous age, the
Alleghanies from New York to Alabama, west of the line of
the Blue Eidge and Highlands, were completed. Thus the
Appalachian chain was a result of a succession of mountain-
making efforts, one producing one part, and the rest others.
The process did not go on twice along just the same range
of country, but to one side of the preceding, either east or
west. Since the completion, the country has been raised as a
whole by a gentle bending upward of the earth's crust,
the lateral pressure in this case, after the mountains were
made, and their rocks folded and consolidated, and the crust
thereby stiffened, producing a slight flexure of the crust and
not any folding of strata.
After the making of the Alleghanies there was mountain-
making of a different kind more to the eastward in the
course of the next age. Along the regions of the Bay of
Fundy, the Connecticut Yalley south of New Hampshire, and
a long range of country from the Palisades on the Hudson
through New Jersey and Pennsylvania into North Carolina
(each region parallel to the part of the Appalachian chain west
MAKING OF CONTINENTS. 93
of it), where several thousand feet of sandstone had been de-
posited, there were made, finally, along with a small upturning
of the strata, a vast number of great fractures of the earth's
crust, the fractures deep enough to let out melted rock; and
this rock, cooled, constitutes the Palisades on the Hudson,
Mount Holyoke in Massachusetts, and various other trap
ridges in the Connecticut Yalley, Nova Scotia, and the more
southern sandstone regions. Here the lateral pressure pro-
duced little upturning, but much fracturing, with extensive
igneous ejections ; and this exemplifies a second method of
action in mountain-making, a method which was most com-
mon in the. later end of geological time, when the earth's
crust had become too stiff to bend easily. After this epoch
of disturbance there were no other general upturnings along
the Atlantic border of the continent. Mountain-making was
there ended long before it was on the Pacific or Eocky
Mountain side, and long before it was in Europe. Neither
these mountains nor the Alps, Pyrenees, or Himalayas were
finished before the close of the Tertiary ; and the grandest of
igneous ejections in the world belong to the same age, the
last before Man.
Another principle connected with mountain-making remains
for consideration. It will be best understood after some of
the facts in geological history have been reviewed; the dis-
cussion of it is therefore deferred to the pages treating of the
formation of the Alleghany Mountains. (See pages 171, 208.)
94 CONCLUSION.
7. Making of continents and the oceanic depression. Con-
traction from cooling also gives a reason for the existence of
the great depressions occupied by the oceans ; for, on this
view, they are the parts of the earth's crust that have sunk
most with the progressing contraction, the parts, therefore,
which were last stiffened, when the crust was in process of
formation; while the continents were the portion that con-
tracted least, or which first became solid.
8. Conclusion. There is thus, in the single fact that the
earth is, and ever has been, a cooling globe, and therefore uni-
versally a contracting globe, an explanation (1) of the gentle
oscillations of level in the earth's surface that have been
quietly going on through all past time; () of the upturnings,
flexures, fractures, faults, and upliftings of strata, and the bend-
ings of the earth's crust, which have resulted in the making of
the great mountain chains of the globe ; (3) of the opening of
fractures down to the deep-seated regions of fire giving exit
to floods of liquid rock and producing volcanoes; (4) of the
alteration of rocks, or their metamorphism, changing the rude
sand-beds and mud-beds into crystalline rocks, and filling fis-
sures with veins of ores and gems; (5) of earthquakes, the
great earthquakes and the larger part of the smaller ones ; and,
finally, (6) an explanation of the origin of continents.
It may be thought that by thus referring to secondary causes
the making and crystallizing of rocks, the placing and raising
of mountain chains, and even the defining of continents, we
CONCLUSION. 95
leave little for the Deity to do. On the contrary, we leave all
to him. There is no secondary cause in action which is not
by his appointment and for his purpose, no power in the ma-
terial universe but his will. Man's body is, for each of us, a
growth; but God's will and wisdom are manifested in all its
development. The world has by gradual steps reached its pres-
ent perfected state, suited in every respect to man's needs and
happiness, as much so as his body; and it shows throughout
the same Divine purpose, guiding all things toward the one
chief end, Man's material and spiritual good.
PART III.
HISTORICAL GEOLOGY.
Subjects and Subdivisions.
HISTORICAL GEOLOGY treats of,
1. The succession in the formation of the rocks of the earth,
and in the conditions under which they were made.
. The progress in the continents, from their small begin-
nings to their present magnitude.
3. The changes of level ever going on, and the raising of
mountains at long intervals in the course of the ages, the
highest and longest in the last of those ages just before the
era of Man.
4. The multiplication of rivers as the dry land extended,
and thereby the excavation of valleys, the shaping of lofty
ridges giving grandeur to the mountains, and the spreading of
the lower lands with soil and fertility.
5. The changes in climate, from the universal warmth of
the Archaean world to the existing variety of heat and cold.
6. The succession in the species under the two kingdoms
HISTORICAL GEOLOGY. 97
of life Plants and Animals from the simpler forms of
early time to Man.
The rocks are sometimes spoken of as the leaves of the
geological record. But these rocks are in various lands, here
some and there others; and how can they be brought into
order ' so as to make a continuous history worthy of confi-
dence ? The case would have been hopeless were it not for one
branch of this history, that relating to the progress of life.
There has been, as above intimated, a succession in the
species of plants and animals that have lived upon the globe.
The earliest kinds were followed by others, and these by still
others, and so on, through age after age, before the final ap-
pearance of Man. The plants and animals that lived in the
successive periods left their relics that is, stems or leaves,
shells, corals, bones, and the like in the mud or sand of
the sea-bottom, sea-shore flats and beaches, and in other depos-
its of the era; and these sand-beds and mud-beds are now
the rocks of those periods. Hence in the rocks of one era
we find different relics, or fossils, from those of the preceding
or following era. Geologists have ascertained the kinds that
belong to the successive rocks, or eras, of the world ; so that,
if they come upon an unknown rock with fossils, in a coun-
try not before studied, it is only necessary to compare the
fossils found with the lists already made out.
Eor a very long part of early time after life was abundant
there were no fishes in the world. The discovery of a fossil
5 G
98 HISTORICAL GEOLOGY.
fish in a bed of rock is, hence, evidence that the bed does
not belong to the formations of that early time, but to 'one
of some later period. After the first appearance of fishes the
kinds changed with the progress of time; so that if, in the
case of our discovery, we can ascertain the tribe to which the
fossil fish we have obtained belonged, we can then decide
approximately the age of the rock which afforded it. No her-
ring, cod, and salmon are known to have existed until near
the last of the geological ages ; and if the species turned
out to be related to these, we should conclude that the rock
was among the later in geological history; and a determination
of the species might lead to the precise epoch to which it
pertained. Bones of beasts of prey, cattle, and horses are
found only in rocks of the last two geological ages.
Thus, owing to the succession of life on the globe, the
geologist is enabled to arrange the fossiliferous rocks in the
order of their formation, that is, the order of time.
If a stratum in one region contains no fossils, or if its fossils
have been obliterated by heat producing metamorphism, the
stratum is traced by the geologist to another region, with the
hope of there discovering fossils, or at least of finding them in
an underlying or overlying stratum. In this and other ways
doubts are gradually removed, and the true succession in any
region is made out.
The history has thereby been divided into four grand sec-
tions :
HISTORICAL GEOLOGY. 99
I. ARCHAEAN TIME; that is, beginning time; the word Ar-
chaan is from the Greek for beginning.
II. PALEOZOIC TIME, or the era of the ancient forms of
life; Paleozoic being from the Greek for ancient and life.
III. MESOZOIC TIME, or the era of mediaeval forms of life;
Mesozoic, from the Greek, signifying middle and life.
IV. CENOZOIC TIME, or the era of the more recent forms
of life ; Cenozoic signifying recent and life.
Paleozoic time, which was probably at least threefold
longer than all later time, has been divided into three ages :
(1) the SILURIAN, or AGE OF INVERTEBRATES; (2) the DE-
VONIAN, or AGE OF FISHES; and (3) the CARBONIFEROUS, or
AGE OF COAL PLANTS. Mesozoic time corresponds to the
AGE OF EEPTILES. Cenozoic time is divided into two ages,
called (1) the TERTIARY, or AGE OF MAMMALS ; and (2) the
QUATERNARY, or AGE OF MAN.
The kingdom of Animals has five great branches, or subdi-
visions, called sub-kingdoms. These are,
1. Protozoans: Microscopic species, with no internal organ
beyond a stomach, and none external unless hair-like or thread-
like appendages. The Rhizopods and Sponges, of which fig-
ures are given on pages 33, 39, are here included. Sponges
are large, but only because each is an aggregate of a great
number of the minute animals. The word Protozoan, from
the Greek, means first or simplest animal.
2. Radiates: Animals having a radiated structure, that is,
100
HISTORICAL GEOLOGY.
Fig. 83.
Astrsea pallida D.
having the parts arranged radiately around a centre, .with the
mouth at or near the centre : as in polyps, the animals of
corals, which look very much like flowers on account of the
radiate arrangement. Each one of the expanded polyps in
this figure of a living coral (Fig. 83) shows well the radiate
character. The Crinoids, represented on page 31, are other
examples of Radiate animals.
3. Mollusks: as the Oyster, Clam, Snail, and Cuttle-fish;
having a soft, fleshy, bag-like body, with sometimes an ex-
ternal shell for its protection, or an internal bone or shell to
give a degree of firmness to the fleshy body.
4. Articulates: as the My, Butterfly, Beetle, and other in-
sects, the Spiders and Centipedes, the Lobster, Crab, and other
Crustaceans, and the Worms : animals having the body made
HISTORICAL GEOLOGY. 101
up of segments or parts jointed together, and having the legs
and feelers jointed. A lobster shows well the jointing of the
body and of all its limbs. Articulate means jointed. The
Lobster, Shrimp, Crab, and some other related animals are
called Crustaceans because they have a crust-like exterior
sometimes called the shell.
5. Vertebrates: as Fishes; Progs, Lizards, Snakes, Croco-
diles, Turtles, and other Eeptiles ; Birds ; the Dog, Cat,
Fig. 84.
Vertebrate.
Pterodactylus crassirostris (X l /4 ).
Horse, Ox, Whale, and other Mammals; animals having in-
ternally, along the back, a series of bones making together
the vertebral column. In Pig. 84, representing one of the
Flying Eeptiles of ancient time, the vertebral column is seen
extending from the head into the tail. Each separate bone
102 HISTORICAL GEOLOGY.
of the column is called (from the Latin) a vertebra. The
great nerve of the body, called the spinal cord, lies concealed
in a tubular bone-sheathed cavity along the upper side of the
column; and below the column there are the ribs and the
cavity for the stomach and other viscera. The Mammals are
those Vertebrates that suckle their young, as the word, from
the Latin, implies. They are the highest of Vertebrates, and
include Man as well as the other animals above mentioned.
Protozoans, Radiates, Mollusks, and Articulates are often
together called Invertebrates, that is, not Vertebrates.
In the table above (page 99), the expressions Age of In-
vertebrates, Age of Fishes, Age of Reptiles, Age of Mammals,
are not to be understood as implying that the several groups
of animals mentioned were confined to the age named after
them, but only that they were the highest, and therefore the
characteristic, species of the age.
Pishes began before the Silurian Age was quite completed,
and continued thence through geological time; but until the
close of the Devonian, or nearly so, they were the highest of
living species.
In the Silurian, until near its close, there were only Inver-
tebrates.
In the Age of Reptiles, the class of Reptiles, which began
in the preceding age, had larger, more numerous, and higher
species than before or afterward; the Age was eminently the
Age of Eeptiles, the type having reached its maximum then,
that is, having culminated.
HISTORICAL GEOLOGY. 103
Mammals of a low order, called Marsupials, existed in the
Age of Reptiles; but in the Age of Mammals the Reptiles
were comparatively few, and true Mammals were the highest
or dominant race.
Again, the Age of Coal-plants was not the only age in
which coal-plants lived and coal was made; but that which
was most remarkable for the making of coal-beds, and espe-
cially for coal-making plants of the tribe of Acrogem, the
highest of Cryptogams or Elowerless plants, such as Ferns,
Ground-Pines or Lycopods, and Horse-tails or Equiseta, which
then grew to the size of tall shrubbery and forest-trees. In
later ages also coal-beds were made, but of less extent, and
mainly out of other kinds of plants. The Carboniferous age
is often called the Age of Acrogens.
Thus the Ages are named after the tribes of each, that were
highest in grade, or those that were most characteristic.
During an age changes of level, or catastrophes of some
other kind, have at intervals produced extensive exterminations
of species over a continental sea, and also abrupt changes in
the kinds of rock-deposits in progress, if not also upturnings
of strata. Each age in the geological history of any continent
has consequently its natural subdivisions, which are called pe-
riods.
The following table gives a general view of the successive
ages, with some of the subdivisions that have been adopted,
the first in time being at the bottom.
104
HISTORICAL GEOLOGY.
Ages.
American.
British.
SUBDIVISIONS.
SUBDIVISIONS.
rS. Recent.
Recent.
[ 2. Quaternary
. . . J 2. Champlain.
Champlain.
CENOZOIC... J
1 X Glacial.
Glacial.
1
f3. Pliocene.
Pliocene.
1 .! Tertiary.
J r' if
.
1 < A. Miocene.
Miocene.
LI. Eocene, including
2. Alabama group, i
1. Lignitic group, j
. Eocene.
HESOZOIC Eeptilian.
PALEOZOIC, j
3. Carboniferous..
2. Devonian
-3. Cretaceous. Cretaceous.
r Jurassic, including
2. Jurassic J 3. Wealden.
2. Oolyte.
1. Lias.
Triassic.
Permian.
Carboniferous.
Mountain limestone.
1
1. Silurian.
Upper.
Lower.
1. Triassic.
C3. Permian.
j 2. Carboniferous.
L 1. Subcarboniferous.
[4. Catskill.
J 3. Portage and Chemung. I
I 2. Hamilton.
^1. Comiferous. J
{4. Oriskany. 1
3. Lower Helderberg.J" ' Ludl ?P-
2. Salina. 1
, _ T . \ Wenlock group.
1. Niagara.]
C 3. Trenton. TLlandeilo and Balagroups.
< 2. Canadian. -I Tremadoc and Skiddaw slates.
LI. Prim'lorCamb'n. [primordial or Cambrian.
AECHJEAN.
The accompanying map (Fig. 85) shows the positions of
the rocks of the successive ages over part of North America,
so far as they are open to view. The markings indicating
the age of the rocks of the several areas are explained on the
map. The black areas are the great coal areas of the conti-
nent. The portions left in white are those the age of which
is not ascertained.
106 HISTORICAL GEOLOGY.
I. Archaean Time.
THE first condition of the earth about which geology gives
any hint is that of a liquid globe, like the sun. The earth
has the form of a sphere flattened at the poles, and as the
amount of flattening is closely that which such a liquid globe
would take as a consequence of its revolution, this fact is
thought to be evidence of an original liquid state. Other
evidence is found in the crystalline character of the oldest
rocks; in the fact that many spheres in space, like the sun,
are still in a liquid state; and in the condition of the moon,
which is like such a globe cooled until its surface is all
craters and scoria.
Admitting that the earth has cooled from fusion, we are
warranted in concluding that, whenever the vapors began to
settle over the solidified but still hot crust, there to make
oceans, the rocks exposed to the heated and acid waters would
have been everywhere eroded by the chemical action of these
waters, and by this means they would have been covered after
a while with new rocks. And over those regions where there
were emerged or submerged rocks within reach^of the waves,
the work of the waves in making gravel, sand, and mud
would have been added to that of the chemical action.
By such means the original rock of the cooled crust would
have become nearly or entirely concealed by new deposits;
ARCH^AN TIME. 107
and it is questioned whether any part of it is now exposed
to view. The rocks made out of that crust not those of
the original crust itself are therefore the Archaean rocks
of geology.
I. Distribution.
The Archaean rocks of North America cover a large sur-
face over the northern portion of the continent, and also some
narrow areas elsewhere along the courses of existing moun-
tains. In the accompanying map (Pig. 86) the white areas
are the regions of exposed Archaean rocks. The largest ex-
tends from Lake Superior northwest to the Arctic seas and
northeast to Labrador. It has the shape of the letter V, and
Hudson's Bay is included within the arms of the V. A
peninsula from it extends down into Northgrn New York,
including there the region of the Adirondacks. Other Ar-
chaean ranges are the Highlands of New Jersey, portions of
the Blue Eidge of Pennsylvania, Virginia, and the region
farther southwest (and including the Black Hills of North
Carolina) ; small areas in New England, and one or more on
the Atlantic border south of New York; a large area south
of Lake Superior ; and the crest range of the Eocky Moun-
tain region, including the Wind-Eiver Mountains and the
eastern range in Colorado.
The arms of the great V, or original nucleus of the conti-
nent, are parallel respectively to the Atlantic and Pacific coast
108
HISTORICAL GEOLOGY.
lines; the other narrower areas follow the courses of the great
mountain chains, and are parallel to the same lines. Geology
thus affords a demonstration that even in Archaean time the
C great outlines of the continent were denned, and that all fu-
NL I ture progress was carried forward by working on the plan
thus early laid down. The rest of the continent was under
wate"r (and perhaps also some of the ridges just referred to),
but it probably lay at no great depth.
Archaean areas exist also in Scandinavia, Bohemia, Scotland,
ARCH.EAN TIME. 109
and some other regions. The facts prove that in Archaean j
time the ocean and continents were, in the main, already ]
outlined. "The waters" of the world had been "gathered
into one place/'' and "the dry land" had "appeared."
2. Rocks.
The Archaean rocks comprise gneiss and granite,' syenyte,
syenytic gneiss, and other hornblende rocks, with chloritic
rocks, quartzyte, limestone, and other kinds.
They include immense beds of iron ore, some of them 100
to 200 feet in thickness, vastly exceeding any in later times;
for the Archaean was the iron age in the earth's history. J ^
These beds of ore occur in Northern New York, Southern
New York and Northern New Jersey, Canada, the Marquette
region south of Lake Superior, in Missouri, where there are
what are called iron mountains, and in many other places.
The beds of ore (i, Fig. 87) alternate with
beds of quartzyte and crystalline schists
or slates, and lie between beds of gneiss
and hornblendic gneiss, or other rocks of
the era, as illustrated in the annexed cut Beds of iron ore
County, New York.
representing a section in Essex County,
New York. Hornblende contains much iron, and this is the
reason why it is so common a constituent of Archaean rocks.
The rocks were originally sedimentary deposits; for the
gneiss, quartzyte, and schists are, as explained on page 71,
110 HISTORICAL GEOLOGY.
altered or metamorphic sedimentary rocks. They were origi-
nally deposits of gravel, . sand, and mud made by the ocean.
The stratification in the gneiss and other rocks is the original
stratification of the fragmental beds.
Like other sedimentary deposits the rocks were laid down in
horizontal beds. But they are now upturned at all angles, and
often foHed, showing thereby that, subsequent to their deposi-
tion, they underwent the great disturbances that attend moun-
tain-making. Fig. 88 shows the general condition of the rocks
Fig. 88.
General view of folds in the Archaean rocks of Canada.
in the Archaean regions of Canada. The Archaean mountains,
including the Adirondacks, the New Jersey Highlands, the moun-
tains of Scandinavia, and others, were then made, if not in part
earlier. The original height of these mountains may have been
many thousands of feet greater than it is now, for all the earth's
agencies of destruction have been engaged in the work of level-
ling them, ever since that first of the geological ages.
Many Archaean rocks much resemble the crystalline rocks of
later time, and as both are without fossils, they may be easily
confounded.
The occurrence of beds of iron ore scores of feet thick is
one means of distinguishing areas of Archaean age. The ore
ARCH^AN TIME. Ill
often contains some titanium, and this is not common in iron \ V
ores of later date. Coarse syenitic rocks and labradorite rocks <*
are characteristic of many Archaean regions, if not exclusively
Archaean.
Sure evidence of Archaean age is obtained when fossiliferous
beds of the lowest Silurian are observed overlying unconform-
ably upturned crystalline rocks, as in Fig. 89. Here the nearly
Fig. 89.
Section from south side of the St. Lawrence, Canada, between Cascade Point and St. Louis Rapids,
i. Gneiss ; 2, Potsdam sandstone.
horizontal Silurian beds referred to, No. 2 and those above,
were laid down after the beds below were made, and also
after their upturning; and consequently the evidence that the
latter belong to anterior time is unquestionable.
3. Life.
The earlier part of Archaean time was necessarily without
life; for until the rocks and seas had cooled down to the
temperature of boiling water, life was hardly possible. Plants
of the lowest orders can bear a higher temperature than the) *J
lowest of animals, and were probably the first living species.
Although the evidence is not conclusive that either plants
or animals were living in the Archaean seas, since if fossils
once were present in the rocks, they have been obliterated by
112 HISTORICAL GEOLOGY.
the crystallization of the beds, the existence then of the sim-
plest kinds is thought to be highly probable. Some of the
beds contain great quantities of graphite, the material of which
lead-pencils are made. Now (1) graphite is nothing but car-
bon (page 9), the essential principle of mineral coal, and (2)
mineral coal was formed from plants; moreover (3) mineral
coal has been found in crystalline rocks converted into graphite.
Here, then, is evidence favoring the probable existence of
plants; and if of any, of Sea-weeds, since the Lower Silurian
has afforded relics of no plants but Sea-weeds. Along with
true Sea-weeds there were probably Diatoms, as these minute
species are the simplest of water-plants.
The occurrence of limestone strata is also thought to favor
the idea of the presence of plants or animals, since the lime-
stones of the world are almost all of organic origin. Masses
somewhat coral-like in texture have been described as fossils,
under the name of Eozoon (from the Greek for dawn-life), and
referred to the group of Ehizopods, described on page 32. But
there is doubt as to their being true fossils, some regarding
them as of mineral origin. Ehizopods are the simplest of all
animal life, and the kind most likely to have been associated
with Diatoms over the sea-bottom.
Whenever the earliest plant, however minute, was created,
a new principle that of life was introduced, which should
subordinate physical forces to its uses. Progress in a system
of life became thereafter the subject of chief interest in the
world's history.
SILURIAN AGE.
113
II. Paleozoic Time.
I. Silurian Age, or Age of Invertebrates.
THE term Silurian comes from a region in Wales where the
rocks occur, and which was formerly occupied by a tribe of
ancient Britons called the Silures. The age is divided into
the era of the Lower Silurian and that of the Upper Silurian.
Fig. 90.
Archaean Map of North America.
The map of the Archaean dry land, here repeated, shows to
the eye the part of the North American continent over which
114
PALEOZOIC TIME.
Fig. 91.
Geological Map of England.
The areas lined horizontally and numbered i are Silurian Those lined vertically (2), Devonian. Those
cross-lined (3), Subcarboniferous. Carboniferous (4), black. Permian (5). Those lined obliquely from
right to left, Triassic (6), Lias (7 a), Oolyte (7 6), Wealden (8), Cretaceous (9). Those lined obliquely from
left to right (10, n), Tertiary. A is London, B, Liverpool, C, Manchester, D, Newcastle.
the following Silurian beds might have been spread out: for
LOWER SILURIAN. 115
the beds are all marine, and must have been made in the part
covered with water, the shaded part in the map. The cir-
cumstances were in the main similar on the other continents.
In Europe (Great Britain included) the Archaean dry land lay(
mostly to the northwest, and the larger part of the rest of the>
continent was receiving marine deposits.
The areas in North America, east of the Rocky Mountain
region, and over which Silurian rocks are exposed to view,
are those which are lined horizontally in the map on page 105.
The Silurian regions in England are distinguished in the same
way on the accompanying map (Fig 91) ; they are confined to
Western England and Wales.
1. Lower Silurian.
1. Bocks.
The rocks of the Lower Silurian era are mainly sandstones]\ x
shales, conglomerates, and limestones.
The same is true for all succeeding eras in geological his-
tory; for sand-beds (the source of sandstones), mud-beds (the
source of shales and argillaceous sandstones), and limestones
have been always in progress from this time onward in some
part of each continental region. Moreover, sand-beds have
never been forming in any region without the making of mud-
beds in the waters not far distant, just as now happens along
sea-shore regions ; for the grinding which produces the former
produces also the latter. Nevertheless, the continental areas
116 PALEOZOIC TIME.
over which sand-beds, mud-beds, and limestones were accu-
mulating have varied greatly through the successive periods,
owing to variations in level and other causes; and at times
the larger part of the continental sea has been given up to
limestone-making.
The following is the succession of Lower Silurian rocks in
North America.
1. In the early part of the era, called the Primordial
(meaning the first in order] , sand-beds now called the Pots-
dam sandstone, from a locality in Northern New York were
spread out over wide areas in North America, and especially
about the shores of the Archaean dry land ; but shales and lime-
stones were forming in some places more or less remote from
these shores.
These earliest Silurian sandstones and shales have the layers
sometimes marked with ripples, or with mud-cracks, or with
the tracks of the animals of the era ; and they thus show that
they were not made in deep water, but, instead, that they were
either the sea-beaches or the off-shore sand-flats or mud-deposits
of the era ; and that part of the time they were above the water's
level, exposed to the drying air or sun, for only thus can mud-
cracks be made.
2. As the era advanced, limestone strata (magnesian lime-
stones, mainly) of great extent were formed over the region of
the Mississippi Yalley, or the Interior region of the continent,
while sandstones and shales with but little limestone were ac-
LOWER SILURIAN. 117
cumulating in the area then a shallow sea now occupied
by the Appalachian Mountains.
3. Next a limestone the Trenton limestone was in pro-
gress over both the Appalachian region from the Green Moun-
tains to Alabama and the Interior region, and also far west and
north, the most extensive limestone formation in the world's
history. The limestone was named from Trenton Falls, on West
Canada Creek, near Utica, New York, where the gorge is cut
through it. It includes the Galena or lead-bearing limestone
of Illinois and Wisconsin.
4. Finally, limestone-making was again confined almost
wholly to the Interior region, and the Appalachian area, in-
cluding New York and the Green Mountains on the north,
was receiving fragmental deposits for sandstones, shales, and
conglomerates.
In Great Britain there are, first, slates and sandstones of great
thickness in the Longmynd and Wales, overlaid by the " Lingula
flags " (the equivalent of the Potsdam sandstone) ; above these,
other slates and flags (laminated sandstones), with some layers
of limestone, including the Llandeilo flags, the Bala beds, and
the Lower Llandovery in South Wales, all making one con-
formable series.
2. Life.
The seas abounded in life, but no trace of anything terres-
trial has yet been found.
The plants found are aft sea-weeds. One of the specimens
118
PALEOZOIC TIME.
is represented in Pig. 92. Some thin deposits of coal occur
in one of the formations, which are supposed to have come
from buried sea-weeds, or else from animal material.
The animals are all Invertebrates ; in other words, no trace
of a Vertebrate, not even of the lowest of Fishes, has yet been
discovered among the animal relics. But all the four sub-
kingdoms of Invertebrates are represented, the Protozoan,
the Eadiate, the Molluscan, and the Articulate.
Figs. 92, 93.
Sea-weed. Sponge.
Fig. 92, Buthotrephis gracilis ; 93, Archsepcyathus Atlanticus.
Protozoans, Among Protozoans there were Rhizopods and
Sponges. One of the Sponges is represented half the natural
size in Pig. 93 a, and a transverse section of it, natural size,
in Pig. 93 b. The irregular cellular structure, with the absence
of radiating plates, is evidence that it is not a coral.
Radiates. The Radiates include Corals, Crinoids, and Star-
fishes. Pig. 94 is a side-view of one of the conical corals of
the Trenton limestone; the top is a cup, radiated with plates,
somewhat like Pig. 15, page 29. When living, the flower-like
LOWER SILURIAN.
119
animal had no doubt its beautiful colors, like those of modern
time, and its aspect may be quite well represented by Fig. 16,
page 30.
Figs. 94, 95.
Polyp-Corals.
Fig. 94, Petraia corniculum ; 95, Columnaria alveolata ; 95 a, top view of same.
Another coral, honeycomb-like in its columnar structure, is
represented in Fig. 95. The cells are radiated, as shown in
Fig. 95 ; but in a vertical section (as seen in such a section of
one of the cells in Fig. 95 a) the cells are crossed by horizon-
tal partitions. The coral has been found in masses several
feet in diameter.
Figs. 96-99 represent some of the Crinoids and Star-fishes.
Fig. 97 shows one of the Crinoids of the Trenton limestone,
though not quite a perfect one, as the arms are broken off at
the tips, and the stem below (by which it was attached to the
rock of- the sea-bottom, and which may have been three or four
inches long) is mostly wanting. The name Crinoid means lily- \
like; but the petals or rays of the flower-like animal consist
of small pieces of limestone (the secretion of the animal) fitting
well together. Fig. 96 shows the form of another kind of
Crinoid, one of very irregular shape; its stem when living
120
PALEOZOIC TIME.
was run down into the mud of the sea-bottom, instead of being
attached to a rock. Figs. 98, 99 are two of the Star-fishes of
the ancient seas, related to the modern Ophiurans.
Figs. 96-99.
Fig. 100.
Asterioids. - Crinoids.
Fig. 96, Pleurocystis filitextus ; 97, Lecanocrinus elegans Crinoids : Fig. 98, Palaeaster matutina ;
99, Taeniaster spinosa.
Mollusks. The Mollusks were of various kinds, all the
principal grand divisions of the class having been represented
by species. Par the most abundant were what are called Brachi-
opods, a group that has comparatively few kinds
in modern seas. One of the earliest Brachiopods
from the Potsdam sandstone had a shell not larger
than a finger-nail; a large specimen of it is rep-
resented in Fig. 100. It is called a Lingnla (or
Lingulella) , from the Latin lingua, a tongue, in allusion to
the tongue-like shape of some species. A related species is
found in the Lingula flags of Great Britain. "When living
LOWER SILURIAN.
121
it was fixed to the sea-bottom by a fleshy stem proceeding
downward from the pointed end or beak of the shell, and
passing into the mud or sand; and as the shells are often in
great numbers together, they must have grown thickly over
the sandy or muddy surface.
Other common Brachiopods from the Trenton limestone are
represented in Figs. 101 to 104.
Figs. 101-104.
102.
Fig. 105.
Brachiopods.
Fig. 101, Leptaena sericea ; 102, Orthis occidentalis ; 103, O. lynx ; 104, O. testudinaria.
The shells have two valves like those of a clam or oyster;
but they are unlike common Bivalves in their symmetrical
form; a line let fall from the beak divides
them into equal halves, whereas in a Clam,
as shown in Fig. 105, such a line divides
the shell very unequally. Moreover, the
mouth in a Brachiopod is at the middle
of the shell, whereas in common Bivalves it is toward one
end (near a, in Fig. 105) ; and further, one valve is the
upper and the other the lower, while in a Clam, and related
kinds, one is the right and the other the left. Thus the
6
122 PALEOZOIC TIME.
animal in this ancient group called Brachiopods has a posi-
tion in its shell just transverse to that of a Clam. The ani-
mal is also peculiar in having two spiral fringed arms, and to
FI ice ^i s the name, from the Greek for arm-foot,
alludes. Fig. 106 shows these arms in a
modern species ; one of the pair is rolled up
spirally in its ordinary position, while the.
other is thrown out. The animal has no
gills or branchiae. The Trenton limestone
was made largely of the shells of Brachio-
Khynchonella psittacea. ^ Crmoids and Corals havmg contr ibuted
little toward it.
The Clam and Oyster and other ordinary Bivalves have a
thin fold of the skin lying like a mantle over the body
against the shell ; then, inside of the mantle and either side
of the body, thin leaf-like gills or branchiae ; and then the
body with no arm-like appendages. In allusion to the thin
lamellar branchiae, they are called LamellibrancJis. There were
some Lamellibranchs in the Lower Silurian, but they were
few compared with the Brachiopods. Fig. 107 represents one
of them, related to the Mussel of modern sea-shores.
There were also some spiral shells, two of them of the
forms shown in Figs. 108, 109. They belong to the tribe
of Gasteropods, so called because the animal crawls on its
ventral surface. The ordinary spiral marine shells, and also
the common snail, are of this tribe. The snail may be often
LOWER SILURIAN.
123
Figs. 107 - 109.
seen crawling thus with its shell over its back; and the
marine species when living, if put into a jar of salt water,
will soon be found in
motion over the glass.
There were also many
species of the highest di-
vision of Mollusks,
those related to the Nau-
tilus, and called Cephal-
j because the animal
Fig. 110.
Mollusks.
haS the head furnished Fig. I07> Avicula Trentonensis ; 108, Murchisonia bicincta ;
109, Pleurotomana lenticularis.
with stout arms for cling-
ing; from the Greek for head and feet. A modern Nautilus,
with the animal in its shell, is represented in Fig. 110. The
shell has transverse partitions, or
is chambered, and in this differs
from the shell of the Snail and
all Gasteropods. The animal oc-
cupies the large outer chamber,
and is peculiar in having large
eyes like a fish, and a series
of stout arms around the mouth
provided with suckers for cling-
ing. A different kind of Cephalopod, from modern seas, is
represented in Pig. Ill, a kind having no external shell,
but instead a thin internal bone (Pig. Ill jo), but with
Modern Cephalopod.
Nautilus (X #).
124
PALEOZOIC TIME.
large eyes and a series of arms around the mouth, as in
the Nautilus. In the Lower Silurian era there were spe-
cies of Nautilus, but quite different ones from those of later
Fig. 111.
Modern Cepbalopod.
The Caiamary or Squid, Loligo vulgaris (length of body, 6 to 12 inches) ; *', the duct by which the ink is
thrown out; f, the "pen."
time. But the earliest Silurian species of Cephalopods and
the largest had straight shells, like that of a Nautilus straight-
ened out, whence the name Orthoceras, meaning a straight
horn. One of them, from the Trenton limestone, is represented
in Pig. 112 ; it has partitions like the shell of the Nautilus.
Fig. 112.
Cephalopod.
Orthoceras junceum.
In both the Nautilus and the Orthoceras a tube (called the
siphuncle, meaning little siphon) passes from the outer cham-
ber through the partitions and all the chambers ; and the
hole in one of the partitions is shown in Pig. 112 a. Some
LOWER SILURIAN.
125
of the shells of species of Orthoceras from the Trenton lime-
stone are as large round as a flour-barrel, and must have been
from twelve to fifteen feet long.
Another kind of Mollusk, of quite minute size, makes cor-
als. The animals look like polyps externally, as shown in
Fig. 113, which represents them enlarged, projecting out of
their cells. Fig. 114 is
a view of one of the deli-
cate Lower Silurian cor-
als, and the dots show
the positions of the little
cells of the animal. The
Figs. 113, 114.
Bryozoans.
- p .^ ii3 Eschara> snowing aniin al s extended out of their cells
( X 8) ; 113 a, one of the animals removed from its cell more en-
- larged; 114, Ptilodictya fenestrata, a Lower Silurian species,
natural size ; 114 a, portion of surface of same enlarged.
are CalleCl
meaning
ma Is, the name alluding
to the corals, which are sometimes moss-like in delicacy and
form. Although so small, these corals are a prominent con-
stituent of some of the Silurian limestones.
Articulates. The Lower Silurian Articulates that have been
made out are either Worms or Crustaceans ; no Insects or Spi-
ders having been present, since these are terrestrial species.
The most remarkable of the Crustaceans, and the highest spe-
cies of the world at the commencement of Lower Silurian time,
and later in this era second only to the Orthocerata, were the
Trilobites, so named because the body has three lobes or
divisions longitudinally, as shown in Figs. 115 to 117. One
126
PALEOZOIC TIME.
of the very earliest species is represented in Pig. 115; it was
a gigantic species, the figure being only one third the natural
length. It has some resemblance to a lobster, and yet is very
different. The position of the large eyes is apparent on the
Figs. 115-118.
Trilobitcs.
Fig. 115, Paradoxides Harlani (X }4); 116, Asaphus gigas (X #) ; 117, Calymene Blumenbachii j 118. same
rolled up, as it is often found.
head shield. Two other species, from the Trenton, are repre-
sented in Pigs. 116, 117. The latter is shown folded up in
Pig. 118, a common condition of the specimens. The forms
of three modern species of Crustaceans having some resem-
LOWER SILURIAN. 127
blance to the ancient Trilobites are shown in Pigs. 119 to 122.
Figs. 121, 122 are female and male of the same species. But
the Trilobites differed from
Figs. 119-122.
all these in having had no
true legs. They are supposed
to have had only thin fleshy
plates, for swimming.
The earliest life of the
Modern Crustaceans.
Lower Silurian was made Fig . 119(aspeciesof Serolis(x ^ ); I2o spedesof Porcel .
, . />/-< i lio ' 181 I22 female and male o{ Sapphirina iris.
up largely or urinoiqs,
Brachiopods, Worms, and Trilobites. It was almost all sta-
tionary life; that is, the most of the species were attached to
the sea-bottom by stems. Such were all the Crinoids and
Brachiopods. Trilobites swam free; but, having only swim-
ming legs, they probably often attached themselves to the rocks,
like the shells called Limpets. Afterward there were Mussel-
like shells and corals, which were also attached species, Mus-
sels living attached to rocks by a byssus or horny threads.
Besides these there were the locomotive species, Gasteropods
and Orthocerata; the latter may have given much activity to
the seas, for Cephalopods are not snail-like in pace, like all
Gasteropods, but fleet movers, like fishes. Yet these ancient
species, with their long unwieldy shells, must have been slow \
compared with the Cephalopods of later time.
The life of the Lower Silurian changed much in species dur-
ing its progress. The era has been divided into three periods :
128 PALEOZOIC TIME.
no animals of the earlier part of the first of these periods
/ the Primordial existed in the second, and none of the
earlier part of the second existed in the third. Moreover,
; species were disappearing and others appearing through each
of the successive periods.
3. Mountain-making.
The close of the Lower Silurian was a time of upturning
and mountain-making in North America, Great Britain, and
I Europe. The Green Mountains, from Canada to southern Con-
necticut, and perhaps other heights to the southwest, were
then made. The rocks which include a great limestone for-
mation (the upper part of which is referred to the Trenton)
and also various fragmental rocks overlying the limestone
were folded and crystallized by the heat produced by the dis-
turbance added to that from the earth's depths, and were thus
changed at the time to metamorphic rocks : the fossiliferous
limestone, to white and clouded crystalline or architectural mar-
ble, of which Canaan in Connecticut, Lee in Massachusetts,
and Eutland in Vermont afford noted examples; the quartzose
sand-beds, to quartzyte; the mud-beds, to gneiss, mica schist,
and other crystalline rocks.
In Great Britain the Lower Silurian formations, which are
throughout conformable, are upturned so as to lie unconform-
ably beneath the beds of the next era, the Upper Silurian.
The elevation of the Westmoreland Hills, of the mountains in
UPPER SILURIAN. 129
North Wales, and of the range of Southern Scotland from St.
AbVs Head, on the east coast, to the Mull of Galloway, has
been referred to this era.
The maximum thickness of the Lower Silurian rocks of >
Britain has been stated to be over 40,000 feet. In the Green -
Mountain region it was probably not less than 20,000 feet; in
Pennsylvania, about 11,000 feet; in Illinois, about 800; in
Missouri, nearly 2,200 feet.
2. Upper Silurian Era.
1. Bocks,
The rocks of the Upper Silurian also are sandstones, con-
glomerates, shales, and limestones.
1. There was first in progress, during what has been called
the Niagara period, the formation which includes the Niagara
limestone, which, like the Trenton limestone, was one of the
great limestone formations of ancient time. In Western New
York and to the southwest along the Appalachian region
still a part of the continental sea the earlier beds forming
were a series of sandstone strata (the Medina sandstone), some-
what pebbly below and argillaceous above; then other argil-
laceous sandstones, and in them a bed of red iron ore, with a
little limestone in the upper part; then the Niagara shale and
limestone, the strata at Niagara Palls, where the upper 80 feet
are limestone and the lower 80 feet shale. To the west of
New York, the Niagara shale formation is of little extent,
6* i
1:30 PALEOZOIC TIME.
while the limestone spreads very widely, reaching into Iowa
and Tennessee.
/ The layers of the Medina sandstone often have ripple-marks,
'; mud-cracks, wave-marks, and other evidences of mud-flat or
7
^ sand-flat origin, showing that Central and Western New York,
with the region to the southwest, was then an area of great
sand-flats over an interior sea; but later this interior sea was
more open and clearer; so that there was less sediment, and
the life required for making limestones flourished.
In Great Britain the Wenlock shale and limestone are of
the age of the Niagara shale and limestone. They are in
view between Aymestry and Ludlow, near Dudley, and else-
where. The limestone, like the Niagara, is full of fossils.
2. Afterward the Salina formation, noted for its salt, was
made. Its clayey rocks and salt show that Central New York,
the borders of Canada to the west, and part of Michigan were
then the site of a great salt basin, where sea-water evaporated,
impregnating the mud of the shallow sea with salt, or making
deposits of rock-salt. The brines of Salina and that vicinity
I [ in New York are salt-water wells, obtained by boring down
to this saliferous rock; and at Goderich in Canada there is
a bed of rock-salt 14 to 40 feet thick. Other salt-bearing
/ rocks were made at the same time in Virginia.
3. Next followed another limestone formation of less extent
than the Niagara, called the Lower Helderberg, from the Hel-
derberg Mountains southwest of Albany, where it occurs. It
UPPER SILURIAN. 131
extends southwestward along the Appalachians; also through
parts of the Mississippi Valley where it rests directly on the
Niagara limestone. It also occnrs at some points in the Con-
necticut Yalley. A sandstone the Oriskany sandstone
overlies it in Central New York and along the Appalachian
region, and in some places to the west, from Ohio to Missouri.
Following the "Wenlock group in Great Britain there is
the Ludlow group, consisting of sandstones, shales, and the
Aymestry limestone, corresponding in age with the later part
of the American Upper Silurian.
2. Life.
1, Plants. As in the Lower Silurian, sea- weeds were abun-
dant; but before the close of the era there were also terrestrial j
plants. The species were not Mosses of the lower division of
Cryptogams, or flowerless plants, and not Grasses, but species of
the Ground-Pine tribe, or Lycopods, a section of the highest)
Cryptogams. They are described beyond, in the account of the
Devonian plants. It cannot be affirmed that there were no
Lichens or Fungi over the Silurian rocky lands, or those of
earlier time ; for such terrestrial species, if existing, would not
have become fossilized, since the rocks are mainly of marine or
marsh origin. But that there were no Mosses may be safely
inferred from the absence of all fossil Mosses from the rocks)
of the following Devonian and Carboniferous ages.
2, Animals. The animals included species of all the grand
132
PALEOZOIC TIME.
divisions existing in the Lower Silurian, Protozoans, Radiates,
Mollusks, and Articulates, with the same great preponderance
of Brachiopods among Mollusks, and Trilobites among Articu-
lates. In addition, before the close of the era, there were
Eishes in the seas, the earliest of Vertebrates. No remains of
terrestrial animal life have yet been found.
A few figures of the Invertebrates are here given. Pigs.
123, 124 represent two of the corals of the Niagara period;
Figs. 123-125.
Polyp-Corals. Crinoid.
Fig. 123, Zaphrentis bilateralis; 124, Halysites catenulata. Crinoid : Fig. 125, Stephanocrinus angulatus.
Eig. 123 related to the coral of the Lower Silurian, figured
on page 119; Eig. 124, a coral imbedded in limestone, which
looks, in a section of the limestone, a little like a chain, or a
string of links, and has hence been called Chain-coral. Eig.
125 shows the form of one of the Niagara Crinoids.
Some of the more common Bracniopods of the Niagara
group are represented in Eigs. 126-128.
UPPER SILURIAN.
133
Figs. 126-128.
127
BracMopods.
Fig. 126, Strophomena rhomboidalis ; 127, side-view of Spirifer Niagarensis ; 128, Orthis bilobus ; 128 a,
enlarged view of same.
The following are figures of two of the larger Trilobites.
Both figures are reduced views, Eig. 129 being but one third
the natural length, and Fig. 130 one fourth.
Figs. 129, 130.
Trilobites.
Fig. 129. LichasBoltoni(X tf); 130, Homalonotusdelphinocephalus(X ja
The fishes were related to the modern Sharks and Gars.
Descriptions of the kinds are given under the Devonian, the
specimens of Devonian rocks being more perfect and afford-
ing better illustrations of the subject.
134 PALEOZOIC TIME.
3. Observations on the Silurian Age.
1. The distribution of the emerged lands of North America
at the close of Archaean time led us to the conclusion (page
108) that the continent was then already denned in area, and
its plan of future progress made manifest. The facts respect-
ing the Silurian rocks sustain this view, and show how the
work of completing the continent went on through the Silu-
rian era. It has already been explained, by reference to the
map of the Archaean dry land, on the same page, that rock-
making, and therefore progress, was confined to the submerged
part of the continent. The map shows the position of the
coast-line along which the waves broke when the Silurian age
began, making the sea-beach deposits and sand-flats that now
form part of the Potsdam sandstone. The Appalachian region
must have been one of the areas of great sand-flats or reefs,
for its eastern side was the course of a range of Archaean
mountains ; and the Rocky Mountain region, for the same
reason, was probably another of the shallower portions of the
continent. The Lower Silurian continental sea had its great-
est depth over the intermediate Interior region, of which the
present Gulf of Mexico was then the southern part. These in-
ferences are sustained by the whole course of the history.
2. With the progress of the Silurian the dry land of the
north received a gradual extension southward, southeastward,
and southwestward. This was the direction of growth. Shore-
SILURIAN AGE. 135
lines of the successive periods were more and more remote
from the old Archaean sea-shore, for the limits of the suc-
cessive formations are farther and farther south; so that, at
the close of the age, the coast-line in the region of the mod-
ern State of New York probably lay a little to the south of
the present Mohawk valley, and, extending westward from
Niagara over Western Canada, it bent northward around Lake
Huron ; thence it turned southward so as to cross Northern
Illinois before taking its course to the far north parallel with
the west side of the Archaean nucleus. These conclusions are
deduced from the limits of the Silurian formations, shown
on the map on page 105.
3. At the close of the Lower Silurian the Green Mountains
were made by an upturning and crystallization of the rocks.
A new area of dry land was thus formed between the seas of
New York and New England, and the valley of Lake Cham-
plain was a consequence of the uplifting. There was also an
upward bending of the earth's crust, but without upturning,
over an area from Lake Erie across the Cincinnati region
to Tennessee, making another spot of dry land. The Green"
Mountains were raised parallel to the neighboring Archaean
Adirondacks ; the Cincinnati uplift was parallel nearly to the
Archaean Blue Eidge. Thus progress was strictly after the
plan laid down in Archaean time.
Southern and Western New York, and the region of the
Alleghany Mountains, remained within the limits of the con-
tinental sea through the Silurian age.
136 PALEOZOIC TIME.
4. The rocks of the Interior region of the continent (now
the great Mississippi valley) were mainly limestones from the
beginning of the Silurian to its close; while those of the
Appalachian region were mainly sandstones, conglomerates, and
s/iales. The Trenton limestone spread over both; but, in
general, there were fragmental deposits forming over the Ap-
palachian region at the same time that there were limestone
deposits in progress to the west of it. The Trenton lime-
stone is an exception; but before the Trenton period closed
the Interior region was alone in limestone-making, the Appa-
lachian having become again, as the rocks show, an area of
mud-flats and sand-flats.
These facts prove that the Appalachian region was a great
reef region through the era, and that over the interior of the
continent there was at the same time a clear and wide sea, one
seldom swept by sediment-bearing currents. The limestones
were made of shells, crinoids, and corals mostly ground up;
and their freedom in general from much impurity shows that
the marine life had there the pure waters in which it best
thrives.
Several of the sandstones and shales contain ripple-marks,
mud-cracks, or foot-prints, proving that they were made, not
in a deep sea, but in shallow waters, and that the deposits
were sometimes exposed above the water's surface.
C5. Over 10,000 species of fossils were described from Lower
and Upper Silurian rocks up to the year 1872. The species
DEVONIAN AGE. 137
continued to change through the Upper Silurian era as well
as the Lower Silurian; that is, the species of the early part
had nearly all disappeared and new species had become sub-
stituted before the later part of the era began; and each of
the successive subdivisions in the rocks indicates some old fea-
ture lost during its progress or in the transition, and some
new feature gained.
2. Devonian Age, or Age of Fishes.
The term Devonian was first applied to the rocks of the
age in Great Britain by Sedgwick and Murchison, and al-
ludes to the region of South Devon, where the rocks occur
and abound in fossils.
Through the age the land had its plants and insects, and
the seas their numerous fishes, besides species of all the lower
orders of life. The regions of Devonian rocks are those ver-
tically lined on the North American map, page 105, and the
map of England, page 114.
1. Rocks.
The Lower Devonian rocks of North America overlie con-
formably the Upper Silurian, making a continuous series with
them.
The age commenced with the era of the Corniferous lime-
stone. This was the great limestone of the Devonian, just as
the Niagara was of the Upper Silurian, and the Trenton lime-
138 PALEOZOIC TIME.
stone of the Lower Silurian. It spreads through New York
from the Helderberg Mountains south of Albany, where it has
been called the Upper Helderberg limestone; and stretches
westward to the Mississippi, and beyond it into Iowa and
Missouri. In New York and along the Appalachian region,
it is underlaid by a sandstone or grit rock.
The limestone is in some places a coral-reef rock, as plainly
so as any coral-reef limestone in modern tropical seas. Near
Louisville, Kentucky, at the Ealls of the Ohio, it consists of
an aggregation of corals, many of large size, and some are
standing in the position of growth. The limestone rock often
contains a kind of flint called hornstone; and, as the Latin
for horn is cornu, the limestone was named the Corniferous
limestone.
The Devonian deposits following this limestone called
often the Upper Devonian are mostly sandstones and shales,
named the Hamilton, Portage, and Chemuug beds, from locali-
ties in New York ; and above these, at the top, there is an
extensive conglomerate and sandstone called the Catskill group.
These fragmental formations are confined mainly to Southern
New York and to the Appalachian region to the southwest.
In parts of the Interior region there were limestones form-
ing when the Hamilton sandstones and shales were in pro-
gress; but subsequent to these limestones the Devonian rock
formed in the Interior region is mainly a shale of little
thickness.
DEVONIAN AGE. 139
The flagging-stone so much used in New York and the
adjoining States is an argillaceous sandstone from the Hamil-
ton beds at Kingston and other places on the Hudson Eiver.
In Great Britain the Devonian formation includes a great
thickness of red sandstone in Scotland, Wales, and England,
which was formerly distinguished as the " Old Red Sandstone/''
In South Devon there are limestone and shales in place of
red sandstone, and hence a greater abundance of fossils. In
the Eifel, Germany, the Eifel limestone is a Devonian coral-
reef rock of the age of the Corniferous. Devonian sandstones
cover a large area in Eussia.
2. Life.
1, Plants. The plants included, besides sea-weeds, various
terrestrial kinds; and among them, in the middle and later
Devonian, large forest-trees.
These early species, as stated on page 131, were mostly of
the higher Cryptogams.
7. Ferns, some of them Tree-ferns. A portion of one of
the Ferns is shown in Fig. 131, and part of the stem of a
Tree-fern in Fig. 132.
2. Equiseta. The modern Equiseta, or Horse-tails (the lat-
ter term a translation of the former) have striated jointed
stems, which may be pulled or broken apart easily at the
articulations. The ancient species had a similar character.
A portion of one of these rush-like Devonian plants is
PALEOZOIC TIME.
Figs. 181, 132.
Ferns.
Hf. .31. NeuropKris ^lymorph, j ,y, TreeJim, Caulopteris aMiqua.
represented in Fig. 133. One of the articulations of the stem
is shown at a b. In allusion to its reed-like character it is
called a Odamit*, from the Latin calamm, a reed The
plant represented in Fig. 134 is supposed by some to belong
the Equ ]S etum tribe ; the word AteroilKto means star-leaf.
134
133
Fig. 133, Calamites transitionis ; 134, Asterophyllites latifolia.
DEVONIAN AGE.
141
8. Lycopods. The earliest land plants, and those most char-
acteristic of the world in ancient time, were the Lycopods.
The little trailing Ground-Pines of our modern woods, so
much used for decorating churches at Christmas-time, are
examples of Ground-Pines; the close resemblance to miniature
Pine-trees is the origin of this name. The earliest of the an-
cient Lycopods were of small size, but some of those of the
Middle Devonian were large forest- trees. Fig. 135 represents
Figs. 135 - 137.
Lycopods. Gymnosperms.
F'g- I 3S> Lepidodendron primaevum ; 136, Sigillaria Hallii. Gymnosperm : 137, Cordaites RobbiL
a part of the exterior of one of the Devonian Lycopods.
The plants are called Lepidodendrids (from the Greek for
scale and tree) , in allusion to a resemblance between the scarred
surface and the scaly exterior of a reptile. The scars are the
bases of the fallen leaves, and resemble the same on a dried
branch from a spruce-tree. In the true Lepidodendrids the
scars are in alternate order, as illustrated in Fig. 135. In
142 PALEOZOIC TIME.
another group, called Sigillarifo, the scars are in vertical series,
as in Fig. 136.
4. Phenogams, or Flowering Plants. Among the Flowering
plants there were trees allied to the Yew, Spruce, and Pine,
kinds having the simplest of flowers, and the seed naked in-
stead of in pods. In allusion to the latter character they are
called Gymnosperms, meaning having naked seeds. The flowers
and fruit are usually in cone-like groups, and in allusion to
the cones a large part of the species are Conifers. Fig. 137
is probably a leaf of one of the Conifers.
2. Animals. Protozoans, Radiates, Mollusks, and Articu-
lates were represented by numerous species, as in the Silurian
age; and among these Brachiopods were the prevailing Mol-
lusks, Corals the most abundant Eadiates, and Trilobites the
most common of Articulates. Three of the Corals of the
coral-reef limestone (Corniferous limestone) from the Falls of
the Ohio, near Louisville, are represented in Figs. 138-140.
Fig. 138 represents a specimen of one of the large simple
Corals, broken at both extremities. The radiating plates are
seen at top. The top, when perfect, had a depression rayed
with such plates, and to this the name of this ancient group
of Corals, Cyathophylloid*, alludes, it coming from the Greek
for cup and leaf. Some specimens of the species are nearly
three inches in diameter at top and a foot long; and, when
living, the polyp or flower-animal when expanded was as large
as a small-sized sunflower, and probably as brilliant in color.
DEVONIAN AGE.
143
Fig. 139 shows the surface of a massive coral whose polyps
covered the surface like those of Fig. 14, on page 29. The
other kind, Fig. 140, is one of the most common ; the structure
Figs. 138 -UO.
iHfcfilfeife*i
138
Polyp-Corals.
Fig. 138, Zaphrantis gigantea ; 139, Phillipsastrsea Verneuili ; 140, Favosites Goldfussi.
is columnar, suggesting that of a honeycomb, and hence its
name, Favosites, from the Latin favus, a honeycomfi.
Besides marine species there were also Insects among ter-
restrial Articulates. Fig. 141 represents a wing of one of
the May-flies of the Devonian world ; a gigantic species much
exceeding any now known. It measured five inches in spread
144
PALEOZOIC TIME.
Fig. 141.
of wings. The May-flies or Ephemerae are species that live
in the water during the young or larval state, and when ma-
ture fly in clouds over moist
places. One of the Devonian
kinds could make the shrill
sound of a locust.
In addition to Invertebrates
there were Fishes among Yer-
tebrates. The remains of the
Fishes are the head, teeth, large spines that formed the front
margin of the fins, and also the whole body with its scales;
but never the back-bone (vertebral column), as this was car-
tilaginous and not bony, and hence decayed on burial.
The species included are (1) Sharks; (2) Gars or Ganoids;
and (3) intermediate kinds called Placoderms.
1. Sharks. The remains of the sharks are eitner the teeth,
the shagreen, or hard, rough-pointed covering of the body,
Fig. 142.
Fin-spine of a Shark.
and the large spines with which the front margin of the fins
are sometimes armed. Fig. 142 represents one of the fin-
spines of a shark of the Corniferous period, two thirds the
full length. The shark was one of great size, as the length
DEVONIAN AGE. 145
of the spine indicates. Some of the sharks had rather blunt,
cutting teeth; but the most common kind, related to the liv-]
ing Cestracion of Australian seas, had a pavement of bony/
pieces over the inner surface of the lower jaw, making the
mouth a formidable grinding apparatus, fit for cracking
Brachiopods and the like.
2. Gars or Ganoids. The Gar-pikes of the Mississippi and
the Great Lakes, now a rare kind of Fish in the world, are
examples of the type of Fishes that was exceedingly abundant
in species in the Devonian Age. The scales of Gars are bony
and shining, unlike those of ordinary modern Fishes, and to
this, Agassiz's name, Ganoid (from the Greek for shining),
refers. In many species the scales are set side by side with
a special arrangement for interlocking at one margin after the
fashion of the tiles on a roof; while in others they are put
on more like shingles, or in the way common in ordinary
fishes. Figs. 143, 144 represent two Figg W3 . U6>
kinds of tile-like scales; and 145, the j^g^ ^ us
under surface of two of the latter,
showing how they are secured to one
another. Figs. 146, 147 represent two
specimens of the Ganoid fishes of the
Devonian. The tail in Fig. 146 has a Scales of Ganoids -
peculiarity that belonged to all of the ancient fishes; that is,
the vertebral column extends to its extremity. In Meso-
zoic and Cenozoic species and modern Gars the vertebral
146
PALEOZOIC TIME.
Figs. 146, 147,
Ganoids.
Fig. 146, Dipterus raacrolepidotus (X '/i) ; 147, Holoptychius ; 147 a, scale of same.
column stops at the commencement of the tail-fin, as in
Tig. 148.
Some of the Ganoids of the Middle Devonian whose re-
mains have been found in Indiana and Ohio were of great size.
Figs. 148, 149.
149
Ganoids.
Fig. 148, tail of Thrissops ; 149, tooth of an Onychodus.
One of them had jaws a foot to a foot and a half long, with
teeth in the lower jaw (Fig. 149) two inches or more long.
DEVONIAN AGE.
147
A Devonian fish between a Ganoid and Shark is repre-
sented in Fig. 150.
Fig. 150.
Cephalaspis Lyellii.
3. Placoderms. Still stranger forms are those called Pla-
coderms. The body of Fig. 151 is encased in bony pieces
Fis?s. 151, 152.
Placoderms.
Fig. 151, Pterichthys Milleri (X #) ; 152, Coccosteus decipiens (X #)
like that of a Turtle, and the length of the species, whose^
remains occur in Eussia and Scotland, is supposed to havey
148 PALEOZOIC TIME.
been twenty to thirty feet. The term Placoderm alludes to the
covering of plates, and is from the Greek for plate and skin.
The teeth of Ganoids are usually very sharp. Sometimes
they are small and fine, and grouped so as to make a brush-
Fig. 153. like surface ; but often they are very
large and stout. The material of
the interior of the teeth, called den-
tine, is intricately folded, and in allu-
s i on to ^ passages of a labyrinth,
such teeth are said to have within a labyrinthine texture.
A simple form of this labyrinthine texture is represented in
Fig. 153.
The facts reviewed with reference to the life of the Devo-
nian teach that during the progress of the age the marshes
and dry land .were covered with jungles and forests; that the
trees were without conspicuous flowers, and the most of them
with no true flowers at all; that the seas were brilliant with
living Corals, as well as Crinoids, and abounded in Bra-
chiopods and Trilobites ; that they also had their great fishes,
Sharks, Gars, and Placoderms. The land, too, had its swarms
of Insects, and probably also its Spiders to spread their webs
for the May-flies, although no relics of them have yet been
found.
3. Mountain-making.
The Devonian age passed quietly for the larger part of the
North American continent, without any tilting of the rocks;
CARBONIFEROUS AGE. 149
yet not without wide, though small, changes of level, varying
the limits and depth of the Interior sea; such changes of
level and of limits being indicated by the varying limits of
the rocks, all of which are of marine origin. This quiet wa*s
not interrupted between the Devonian and Carboniferous eras,
as far as yet discovered, except to the northeast in the region
of New Brunswick, Nova Scotia, and Northeastern Maine.
There an upturning and flexing of the beds occurred, and,
as a result, some mountain-making.
The southward extension or growth of the dry land of the
continent continued; and, by the close of the Devonian, the
shore-line probably crossed the southern portion of what is
now the State of New York, where is the southern limit
of the outcropping Devonian, so that all of Canada except the
southwest extension north of Lake Erie, nearly all of New
York, and much the larger part of New England, were above
the sea-level, together with Wisconsin and the borders of the
adjoining States. There was probably also an island, trending
north-northeast, over the Cincinnati region (page 135), and an-
other about an Archaean area in Missouri. See map, page 105.
3. Carboniferous Age, or Age of Coal-Plants.
The Carboniferous age was the time when the most exten-
sive coal-beds of Europe and America were formed. The
name Carboniferous is from the Latin carbon, coal.
150 PALEOZOIC TIME.
1. Rocks. Coal-measures.
1. The age commenced with a marine period, the Subcar-
boniferous, in which a large part of the North American
continent was under the sea, though not at great depths, and
Great Britain and Europe also were to a large extent sub-
merged. During it, limestone strata, with some intervening
sand-beds, were in progress in portions of Great Britain and
Europe, and over much of the Mississippi basin or the In-
terior region; and, at the same time, great fragmental depos-
its, making sandstones, shales, and conglomerates, were laid
down along the Appalachian region from the borders of New
York southwestward, the thickness of which was five times as
V great as that of the limestone strata.
The limestone was formed to a great extent of Crinoids, and
has been called Crinoidal limestone. The Crinoids were of
numerous species and very various forms. One of the most
perfect specimens is represented in Fig 154, only the stem
below being wanting. The figure shows the numberless stony
pieces really blocks of limestone material of which it con-
sists, and which ordinarily fell to pieces when the animal died,
as there was little animal membrane to hold them together.
The animal opened out its arms at will, and when expanded,
the breadth of the flower-like summit in this species was
about three inches. The stem below, when entire, was prob-
ably a foot or more long. The little disks of which the stem
CARBONIFEROUS AGE.
151
in Crinoids consists, looking like button-moulds, are common
fossils in the limestones. (See page 34.) Some of them are
an inch in diameter. Fig. 155 represents another kind of
Crinoid, which was without_ams, called a Pentremites, from
the Greek for Jive, the form of the stem being approximately
five-sided.
Figs. 154-156.
Crinoids. Coral.
Fig. 154, Zeacrinus elegans ; 155, Pentremites pyriformis. Coral : 156, surface of Lithostrotion Canadense.
There were also Corals; and a top view of the most com-
mon of these is represented in Fig. 156. Brachiopods also
contributed largely to the rock, as to all earlier limestones :
figures of two of them are given in Figs. 157, 158.
2. After the Subcarboniferous period a period of submer-
gence began the true Coal period, or that of the Coal-meas-
ures, as the series of coal-beds and rocks containing them is
called. The rocks are mostly sandstones, shales, and conglom- )
152 PALEOZOIC TIME.
crates; but in the Interior region of North America there
/ are some intervening limestone strata. The rock at the base
of the coal-measures is generally a conglomerate called the
millstone-grit.
157
Brachiopods.
Fig. 157, Spirifer bisulcatus ; 158, Productus punctatus.
The Coal-beds contain only terrestrial or fresh-water fossils,
and nearly all are plants; while the strata that separate them
have sometimes marine or brackish water fossils.
The areas of the coal-measures are the black areas on the
maps of North America and England, pages 105, 114.
In North America there is one area, the Acadian, to the
northeast in Nova Scotia and New Brunswick; a second, of
very small extent in Ehode Island; a third, the Alleghany,
reaching from near the southern boundary of New York over
part of Pennsylvania, Ohio, Kentucky, and Tennessee to Ala-
bama ; a fourth, in Central Michigan ; a fifth, the Eastern In-
terior, covering parts of Illinois, Indiana, and West Kentucky;
a sixth, the Western Interior, over parts of Iowa, Missouri,
CARBONIFEROUS AGE. 153
Kansas, Arkansas, and Texas. The last two were originally
united in one, the Mississippi valley now separating them.
It has been estimated that the area of the workable coal-beds
of the United States is at least 120,000 square miles. The
coal area of Nova Scotia and New Brunswick is 18,000 square
miles.
The principal coal areas of England are those of South
Wales; the great Lancashire region east of Liverpool (B, on
the map, p. 114) and Manchester (C) ; the Derbyshire coal
region farther east; and on the northeastern coast, the New-
castle coal-field (D). There are also coal-fields in Scotland
between the Grampian range on the north and the Lammer-
muirs on the south ; and others, of Ulster, Connaught, Leinster
(Kilkenny), and Munster, in Ireland. The areas of England
and Scotland are supposed to have been originally one great
coal-field. There are valuable coal-fields of smaller extent in
Belgium, Prance, and Spain, and stjll^smaller in Germany andj
Southern Russia.
The greatest thickness of the coal-measures in Pennsylvania^
is 4,000 feet; in Illinois, 1,200 feet; in Nova Scotia, about
15,000 feet. In Great Britian it is 7,000 to 12,000 feet in
South Wales, and contains a hundred beds of coal ; 7,000
feet in Lancashire, with forty beds of coal; 2,000 feet at
Newcastle. The aggregate thickness of the coal-beds of a
region is not over one fiftieth, of that of the coal-measures.
The coal-beds vary in thickness from less than an inch to
7*
154 PALEOZOIC TIME.
30 or 40 feet. The " mammoth vein" of the anthracite re-
gion in Pennsylvania is 29 feet thick at Wilkesbarre; but
there are some layers of shale in the course of it, a common
fact in all coal-beds. Some coal-beds contain too much earthy
matter to be of any value.
The mineral coal is of different kinds. That of Central
Pennsylvania and of Rhode Island is anthracite, while that
of the rest of the country is almost wholly bituminous coal.
Anthracite is a firm lustrous coal/ burning with but little
flame, while the bituminous coal, as that from Pittsburg and
the States west, is less firm and usually of less lustre, and
burns with much yellow flame. The flame is due mainly to
the fact that part of the carbon is combined with hydrogen (or
with hydrogen and oxygen) into a compound that, when heat
is applied, becomes a combustible gas or mineral oil. Bitu-
minous coal when heated affords more or less of mineral oil
(the material from which kerosene is obtained), although it
\ contains none ; the oil or gas is produced by the heat out of
some carbonaceous material present. Some bituminous coals
especially those compact coals, scarcely shining, called can-
ne l coa l afford 50 per cent or more of volatile matter;
while anthracite yields very little, and this is mostly the vapor
of water.
Coals always contain some impurity which is the " ashes "
and " clinkers" of a coal-fire. This ashes or earthy mate-
rial was largely derived from the plants themselves, and for
CARBONIFEROUS AGE. 155
the best coals wholly so; but in other cases it is part of the
detritus that was from time to time washed over the beds
of vegetable debris when they were forming. The coal-beds
always contain a little sulphur, enough to give a sulphur
smell to the gases from the burning coal; and the most of it
comes from the presence of _pyrite, a compound of iron and
sulphur.
The layer of rock under a coal-bed is often a clayey layer,
called the underclay, and it is frequently full of the
under- water stems or roots of plants. The trunks sometimes
project from the top of a bed of coal, as shown in Fig. 65,
page 84. Many logs or great trunks lie in the strata that
intervene between the coal-beds, which were once floating logs ; j
and multitudes of ferns and flattened stems or trunks of these
and other plants are often spread out in the shales, and espe-
cially in the bed of rock directly over a coal-bed. Moreover,
the coal itself, even the hardest anthracite, has sometimes im-
pressions of plants in it, and, more than this, contains through-
out its mass vegetable fibres in a coaly state which the
microscope can detect.
Coal was made from plants, and each coal-bed was origi-
nally a bed of vegetable material like the peat-beds of the
present time in mode of accumulation. (See, on this point,
page 40.) The plant-bed having accumulated until several
times thicker than the coal-bed to be made out of it, was
finally covered with beds of clay or sand; and while thus
buried it gradually changed to coal.
156 PALEOZOIC TIME.
Plants when dried are one half carbon, the chief material
of charcoal, the rest being mostly the two gases oxygen and
hydrogen; after the change, eight tenths to nine tenths or
more of the whole are carbon.
3. The coal-measures are followed in Europe by a series
of red sandstones and clayey rocks or marlytes, with a mag-
nesian limestone, constituting the Permian group, so called
from the district of Perm, in Russia. In North America the
Permian rocks include the sandstones and shales at the top
of the coal-measures in Kansas.
2. Life.
1 Plants. The plants were similar in general character to
their predecessors in the Devonian age, though mostly dif-
ferent in species and partly in genera. Of the higher Cryp-
togams called Acrogens (or upward growers, as the word
from the Greek signifies) , because they can grow into trees
there were (1) Ferns, (2) Equiseta, (3) Lycopods ; and of
the Phenogams, or flowering trees, there were Conifers, or plants
of the Pine-tribe. The trees and shrubs grew luxuriantly
over the almost endless marshes of the continent, and spread
also beyond them over the higher lands.
The features of the vegetation and of the ordinary land-
scape is shown in the following ideal sketch. The tree at
the centre is a Tree-fern, and there are smaller Ferns below.
The tree near the left side is a Lycopod of the ancient tribe
CARBONIFEROUS AGE.
157
of Lepidodendrids ; and in the right corner there are other
Lepidodendrids and the trunk of a Sigillaria. In the left
corner there are Equiseta. The region is represented as a
Fij?. 159.
Carboniferous Vegetation.
great marshy plain with lakes. The lakes of the Carbon-
iferous era probably had their many floating islands of vege-
tation, carrying large groves like the floating islands of some
lakes in India.
158
PALEOZOIC TIME.
Fig. 160.
Fern.
Sphenopteris Gravenhorstii.
A portion of one of the Perns is shown in Pig. 160, and
of another in Pig. 161. Pig. 162 represents one of the Equi-
Fig. 161.
Neuropteris hirsuta.
seta, a species of Calamites (page 140) ; plants with jointed
stems that grew often to a height of 20 feet, and sometimes
Fig. 162.
Equisetum.
Calamites cannseforniis.
CARBONIFEROUS AGE.
159
were a foot in diameter, very unlike the little Horse-tails
of modern time.
The Lycopods of the tribe of Lepidodendrids had the as-
pect of Pines and Spruces, and were 40 to 80 feet or more
in height. On some, the slender pine-like leaves were a foot
or more long. Figs. 163, 164 show the scars of the outer
163 - 165.
163
Lycopods.
Fig. 163, Lepidodendron clypeatum ; 164, Halonia pulchella ; 165, Sigillaria oculata.
surface of two of the Lepidodendrids arranged, as usual, in
alternate order; and Eig. 165 those of a Sigillaria in vertical
series. The resemblance of the scars in the latter to an im-
pression of a seal suggested the name Sigillaria y from the
Latin Sigilla, seal.
The cones of the Lepidodendrids and Conifers and the
nuts of the latter also occur in the beds. Two of these nuts
160
PALEOZOIC TIME.
are represented in Figs. 166, 167. They are supposed to
have belonged to trees related to the modern yew-tree.
Nearly 500 species of Carbonif-
erous plants have been described
from North America, and about
the same number from Europe ;
and of these more than one third
were common to Europe and
America.
There are also coal-regions in
the Arctic islands which have af-
Nuts of conifers, forded some of the same species of
Fig. 166, Trigonocarpus tricuspidatus ; 167,
T.ornatus; 168, view of lower end of same. plants that W6rC growing in Eu-
rope and America, showing great uniformity in the climate
of the era; a fact sustained also by the occurrence in the
Arctic deposits of many fossil shells and corals identical with
some then living in the seas of Europe and America.
2. Animals. The seas of the Carboniferous age abounded
in Crinoids and Corals among Eadiates, and Brachiopods far
exceeded in number all other kinds of Mollusks; but in the
group of Articulates, while there were many kinds of Worms
and Crustaceans, Trilobites were few. Trilobites had been
replaced by other Crustaceans, some of which were much like
the modern Shrimp. Examples of the Crinoids, Corals, and
Brachiopods of the earlier part of the age are figured on
pages 151, 152.
CARBONIFEROUS AGE. 161
Fishes were in great numbers and of large size, and they
belonged to the two grand divisions that were especially char-
acteristic of the Devonian, the Sharks (called also Sela-
chians, from the Greek for cartilage, the Sharks being fishes
with a cartilaginous skeleton) and the Ganoids. One of the
Ganoids of the coal-measures is represented in Fig. 169. It
Figs. 169, 170.
170,
Fishes.
Ganoid : Fig. 169, Eurylepis tuberculatus, from the coal-formation in Ohio. Selachian : Fig. 170, tooth of
Carcharopsis Wortheni ; a, profile of section of same.
has the vertebrated tail characteristic of all Paleozoic fishes.
Fig. 170 shows the form and size of the teeth of one of the
sharks of the Illinois region.
The land had its Insects, true Spiders, Scorpions, and Cen-
tipedes, and also its land Snails ; and among the Insects there
were May-flies, Cockroaches, and Crickets. A view of one of
the May-flies, twice the natural size, is shown in Fig. 171 ;
of the wing of a Cockroach in Fig. 172; of a Spider, from
Morris, Illinois, in Fig. 173; and of a Centipede, from Nova
Scotia, in Fig. 174.
Besides these species there were also Reptiles, the earliest
162
PALEOZOIC TIME.
relics of which thus far found come from Carboniferous rocks.
Footprints of them have been described from the Subcarbon-
Figs. 171-174.
174
Terrestrial Articulates.
Fig. 171, Miamia Bronsoni (X 2) ; 172, Blattina venusta, wing of a Cockroach. Spider : Fig. 173,
Arthrolycosa antiqua. Centipede : Fig. 174, Xylobius sigillarise.
iferous beds of Pennsylvania, indicating a large animal having
a tail, the tail having made its mark on the mud-flat over
CARBONIFEROUS AGE.
163
Fig. 175.
which the animal marched. In the Carboniferous beds of
Illinois, Ohio, and Nova Scotia skeletons have been found.
One of them, from Ohio, is represented in Pig. 175. It
has the broad cranium with
large open spaces that is
found in the Erog and Sala-
mander; but while modern
species have a naked skin
and no teeth, the Carbon-
iferous kinds were furnished
with scales and sharp teeth
very much like those of)
the Ganoid fishes. Progs'
and Salamanders belong to
the inferior division of Rep-
tiles called Amphibians.
They are distinguished from
true Reptiles (such as Liz-
ards, Crocodiles, Snakes,
Turtles) by having gills
when young, which serve
them for respiration until
they become full grown ; then the gills drop off, and they
use their lungs. The Carboniferous species are believed to
have had this low fish-like character in the young state, and
thus to have been related to the modern Frog and Salaman-
164 PALEOZOIC TIME.
der, or Amphibians; but, while so, they were greatly superior
to the modern representatives of the tribe.
Besides these Amphibians, there were also true Reptiles.
Fig. 176 represents a vertebra of one of them, from the
Nova Scotia coal-measures. The
Figs. 176, 177. . .
vertebra, as the section in .big.
177 shows, was concave on both
surfaces like those of fishes, and
also like those of the sea-sau-
rians, found in the rocks of the
next geological age, reptiles
Fig. I7 6, Vertebra E Acadicus, Marsh; that had paddleS like whaleS.
177, profile of same. .,, -i /> , i i -\ *>
Finally, before the last period of
the Carboniferous age had passed, there were also still higher
Eeptiles, those that lived on the land.
No remains of Birds or of Mammals have yet been found
in any rocks as early as those of the Carboniferous age.
3. Changes during the Progress of the Carboniferous Age.
Changes of level were going on over the North American
continent throughout the Carboniferous age; but they were
oscillations above and below the sea-level in many alternations,
and of the gentlest and slowest kind possible, and not uplift-
ings into mountains. Just such alternations of level had been
in progress all through the preceding ages; but the Carbon-
iferous movements were peculiar in this, that the continent
CARBONIFEROUS AGE. 165
over its broad surface was just balancing itself near the wa-
ter's surface, part of the time bathing in it and then out
in the free air, and so on, alternately; while, in former times,
the oscillations seldom carried the interior region out of the
sea, or if it did, only portions at a time. It was peculiar
also in the fact that the wide continent lay quiet above the
sea-level, with a nearly even surface, for a very great period
of time, sufficiently long to make beds of vegetable debris
thick enough for coal-beds; many of the coal-beds are six
feet thick, and some twenty or more ; and even six feet would (
require, according to an estimate that has been made, a bedh
thirty feet thick for bituminous coal, and a much thicker one/
for anthracite.
The Interior of the continent from Eastern Pennsylvania to
Central Kansas was a region of vast jungles, lakes with float-
ing grove-islands, and some dry-land forests, and the debris
of the luxuriant vegetation produced the accumulating plant-
beds. A Cincinnati area of emerged land then divided the
continental marsh from Lake Erie to Tennessee; but farther^
south the eastern and western portions were probably united. J
The Michigan coal area was an independent marsh region.
The Green Mountains separated the Pennsylvania area from
those of New England and Nova Scotia; but the two latter
were probably connected along the region of the Bay of Fundy
and Massachusetts Bay.
The changes of level could hardly have carried up evenly
166 PALEOZOIC TIME.
all parts of the Interior marsh-region from Pennsylvania to
beyond the Mississippi; and it is evident that they did not,
since it is difficult to make out the parallelism between the
beds of the eastern, central, and western portions.
The era of verdure during which a plant-bed was in pro-
gress finally came to its end by a return of the salt water
over the continental interior which destroyed the terrestrial
life; and then began the deposition of sediment covering up
the plant-beds and making sandstones or shales or conglom-
erates, or the forming of limestones. Finally, the continental
surface, or wide portions of it, again emerged slowly, putting
an end to its marine life, and opening a new era of verdure.
Such alternations continued until all the successive coal-beds
were made ; some of them affecting perhaps the whole breadth
of the Interior coal area, others more local. Thus the era was
one of constant change ; yet change so gradual that only a being
whose years were thousands or tens of thousands of our years
would have been able to discover that any was in progress.
In Nova Scotia the oscillations went on until nearly 15,000
feet of deposits were formed; and in that space there are 76
coal-seams and dirt-beds; and therefore 76 levels of verdant
fields between the others when the waters covered the land.
But over that region the waters submerging the region were
mainly fresh or brackish waters, since no marine shells exist in
the beds, while there are land shells and bones of reptiles.
The area was an immense delta in the Carboniferous age at
APPALACHIAN REVOLUTION. 167
the mouth of the St. Lawrence, then the only great river of
the continent, and the submergences were connected with the
floods of the stream as well as changes of level in the crust
of the earth beneath.
The Permian period, or the closing part of the Carbonifer-
ous age, was an era of gradual submergences, without long
eras of verdure or the formation of plant-beds.
4. Mountain-making at the close of Paleozoic Time.
From the beginning of Paleozoic time to its close all changes
over the Appalachian region west of the Archaean ridges, south-
west of New England, and over the great Interior region of the
continent, had gone on quietly, with gentle oscillations of the
surface and slight displacements, but no general upturning in
any part.
These ages of quiet and regular work in rock-making were 1
very long, for Paleozoic time includes at least three fourths J V
of all time after the commencement of the Paleozoic.
Over the Appalachian region from New York southward,
the Silurian, Devonian, and Carboniferous deposits have great
thickness. The amount in Pennsylvania and Virginia has been '
estimated at 40,000 feet, or over seven miles. But over the
Interior region, where limestones were the most of the time
forming, the thickness is from 3,000 to 4,000 feet. These
Appalachian deposits, more than ten times thicker than those
of the Interior, were accumulating there for the making of a
168 PALEOZOIC TIME.
range of mountains; and at the close of the Paleozoic all was
ready and the mountains were made.
These 40,000 feet of deposits were laid down in a great
trough made by the gradual sinking of the earth's crust. Eor
the lowest sandstone of the series bears evidence that it was
made in shallow waters, as stated on page 116; and the last
in the series, the Carboniferous beds, were spread out hori-
zontally just above or just below the surface, the coal-beds
proving a small emergence part of the time, and ripple-marks,
mud-cracks, and footprints indicating that the sea-level was
near by. The coal-measures contain beds of iron ore of great
economical importance; and these are evidence that the con-
dition was at times that of a great muddy marsh, probably a
salt marsh, the iron ore being a marsh deposit.
If, then, the top and bottom strata were made near the
water-level, there must have been seven miles of sinking dur-
ing the interval between their deposition. Other beds of the
series bear like evidence of shallow- water origin; so that the
fact is clear that the earth's crust, along what is now the
region of the Alleghany Mountains, west of the Blue Ridge,
for a breadth of nearly a hundred miles and a length of seven
hundred and fifty or more, was slowly sinking, so slowly
that the sediments laid down kept the trough all the time
full to the surface, or nearly so.
This sinking of the earth's crust over the region, and the
concurrent accumulation of sedimentary beds, were the pre-
APPALACHIAN REVOLUTION. 169
paratory steps in the mountain-making that was then to go
forward, and steps that took, as above remarked, three fourths
of all geological time after the Archaean era.
The catastrophe consisted in the (1) folding, (2) fracturing,
(3) solidifying, and in part (4) crystallizing of the beds; and
also (5) in the change, in Central Pennsylvania, of bitumi-
nous coal to anthracite.
The folds were numerous, and involved the whole breadth
of the region; and if their tops had not since been worn off
by the action of water, some of the folds would now rise \
over 10,000 feet above the sea-level. Their characters are j
shown in Fig. 178, of a section from Virginia, extending
Fig. 178.
fly # - ^yy^^^^^.x.--.^^^
from the southeast on the right to the northwest on the left,
over a distance of six miles. It presents an example, as
explained on page 84, of the denudation the country has
undergone, as well as of the folding.
The coal-formation was involved in the folds, a fact
which proves that the folding began after the coal-beds were
formed. Pig. 179 is a section from the vicinity of Potts-
ville, Pennsylvania, P being the position of Pottsville on the
coal-measures. Pig. 180 represents another from near Nes-
quehoning, Pennsylvania, showing the anthracite beds doubled
up, and in part vertical.
8
170
PALEOZOIC TIME.
1. The folds are steepest and most numerous to the south-
eastward, or toward the ocean, and diminish to the northwest-
ward. (See Fig. 178.)
Figs. 179, 180.
Sections of the Coal-measures.
Fig. 179, on the Schuylkill, Pa. ; P, Pottsville on the coal-measures ; 14, the coal-measures ; 13 to n, Devonian
formations ; 8 to 5, Upper Silurian ; 4 to 2, Lower Silurian. Fig. 180, Anthracite region, near Nesquehon-
ing, Pa. ; the black lines coal-beds.
2. The folds generally have the western slope steepest, as
if pressure from the direction of the ocean had pushed them
westward; and sometimes the tops have thus been made to
overhang the western "base. (Fig. 179.)
Fig. 181. I
Section of the Paleozoic Formations of the Appalachians, in Southern Virginia, between Walker's
Mountain and the Peak Hills (near Peak Creek Valley).
F, fault ; a, Lower Silurian limestone ; b, Upper Silurian ; c, Devonian ; d, Subcarboniferous, with coal-beds.
3. The rocks were also fractured on a grand scale, and
those of the eastern side of the fracture shoved up so as to
make faults in some cases of more than 10,000 feet. Fig.
APPALACHIAN REVOLUTION. 171
181 represents one of these great faults. The fault is at F;
to the right of F is the coal-formation, and to the left, a bent-
up Lower Silurian limestone; so that a Lower Silurian rock
is brought up to a level with the coal-formation, a lift, ac-
cording to Lesley, of 20,000 feet.
4. The rocks were solidified through the aid of the heat
caused by the movement of the rocks (page 72) ; and by
the same means the change of the coal to anthracite was
caused. This change to anthracite took place where the rocks
are most upturned; it diminished westward, and accordingly
the coal, on going west, is first a semi-anthracite or a semi-
bituminous coal, and then true bituminous coal, as at Pitts-
burg. The rocks in some regions were crystallized.
5. While there was so much folding and fracturing, there
was no chaotic confusion of the rocks produced, the stratifi-
cation being perfectly retained.
It follows from the facts (1) that the force acted quietly,
or with extreme slowness, for otherwise confusion would
have been produced; and (2) that the pressure acted from
the direction of the ocean, the forms of the folds and their
greater numbers and steepness in that direction proving this.
Now, what was the action producing the folding and accom-
panying effects?
The earth's crust below the region rested at the time on
liquid rock; if it did not, the trough 7 miles in depth
could not have been made by the downward bending of the
172 PALEOZOIC TIME.
crust. Suppose the thickness of the crust to have been at the
time 100 miles; and that below 100 miles there was fusion
and the temperature of fusion. In the making of the trough
the crust was bent downward, and as it formed it was kept
full of sedimentary beds; so that, at the close of the Car-
boniferous age, the distance from the surface to the original
bottom of the bent crust was increased by 7 miles, making
it 107 miles. If, then, the distance down to the temperature
of fusion was 100 miles, the bottom of the. crust beneath the
trough for a thickness of 7 miles must have been wholly
or partly melted off. The crust would have been greatly
weakened by such a loss, and also by the heat penetrating
upward into it; for it had received no corresponding increase
of strength from the 7 miles of deposits added, since these
were not wholly consolidated. As a consequence, the pressure
from the direction of the ocean, resulting from the earth's
contraction (page 89), the same that had been making the
trough, produced finally a break below and a collapse, and
thereby a pressing together of the thick deposits lying in the
trough, folding and breaking them ; and also raising the upper
surface above its previous level, because the width of the base
on which they rested was narrowed by the collapse.
These facts respecting the formation of the Alleghany Moun-
tains illustrate the way in which other mountains of folded
rocks have been made. The Green Mountains had a similar
history : first, a slow subsiding of the crust making a trough,
APPALACHIAN REVOLUTION. 173
and a trough that was kept full of sedimentary deposits, and
which took the whole of the long Lower Silurian era for its
completion (probahly half the whole length of Paleozoic
time) ; then a break below, and a collapse producing folds
and fractures throughout the region; contemporaneously, the
production of heat as a consequence of the friction of the
folding and fracturing rocks, which was added to the heat
that had come up into the strata from the depths below dur-
ing the sinking; and the solidification and metamorphism of
the various rocks as a consequence of the heat.
Mountains were made in Europe and Great Britain at the
same time with the Alleghanies, so that the close of Paleozoic f
time has its mountain boundary elsewhere besides in America. S
Changes in Paleozoic Life at the Close of the Era.
In Paleozoic time Crinoids, Brachiopods, Cyathophylloid
Corals, Orthocerata, Trilobites, vertebrate-tailed Ganoid Pishes,
and Lepidodendrids, Sigillarids, and Calamites among plants,
were characteristic species in each of the classes to which
they belong. With the close of it, Trilobites, Lepidodendrids,
and Sigillarids became extinct; Cyathophylloid Corals, Ortho-
cerata, and vertebrate-tailed Ganoids nearly so; and, after-
ward, Brachiopods among Mollusks, and Crinoids among
Radiates, were greatly inferior in numbers and importance to
other types of more modern character. It is thus that the
Paleozoic features of the world passed by.
174 MESOZOIC TIME.
The characteristics of the following era, the Mesozoic, had
in part appeared before the Paleozoic era closed. Eor Am-
phibians and true Eeptiles were then in existence, Shrimps
and other species among Crustaceans and Insects, Spiders, and
Centipedes among Articulates. And the grand division of
plants which had its maximum display in the Mesozoic
the Cycads, of which an account is given beyond had some
species before the age closed.
The extinction of species at the close of the Paleozoic was
so nearly universal that, thus far, no fossils of the Carbonif-
erous age have been found in rocks of later date. But the
rocks now in view were those that were made over the conti-
nental seas, and, more correctly, over only portions of those
seas; and hence they give no facts as to the species of the
ocean, and but an imperfect record of those of the continental
III. Mesozoic Time.
MESOZOIC TIME includes only one age, the age of Eeptiles.
The Mesozoic areas on the maps of the United States and Eng-
land, pages 105 and 178, are lined obliquely from the right
above to the left below.
Age of Reptiles.
This age is divided into three periods :
1. The TRIASSIC: named from the Latin tria, three, in
allusion to the fact that the rocks in Germany have three
subdivisions.
REPTILIAN AGE. 175
2. The JURASSIC : named after the Jura Mountains, on the
eastern borders of Erance.
3. The CRETACEOUS : named from the Latin creta, chalk, the
formation including the chalk-beds of England and Europe.
1. Rocks.
By the close of the Paleozoic, the Interior region of the
American continent east of the Mississippi had become dry
land. Accordingly, Triassic and Jurassic rocks were formed
only on the Atlantic border east of the Appalachians, and
over the western half of the continent beyond Missouri.
These rocks on the Atlantic border cover long narrow areas
parallel with the Appalachians from the Gulf of St. Lawrence
southwestward. One of them lies along the east side of the
Bay of Fundy ; another in the Connecticut valley from Northern
Massachusetts to New Haven on Long Island Sound ; another,
commencing in the region of the Palisades, extends through
New Jersey and Pennsylvania into Virginia; and others occur
in Virginia and North Carolina. These areas are indicated on
the map on page 105.
The rocks are mainly red sandstones. In Virginia, near Eich-
mond, and in the Deep River region, North Carolina, there are
thick beds of good mineral coal. They contain no marine fos-
sils ; the few that occur are either brackish-water or fresh- water.
It follows, hence, that the long narrow ranges of sandstone were
formed in valleys, parallel with the Appalachians, into which,
for some reason, the sea did not gain full entrance.
176 MESOZOIC TIME.
In Western Kansas, and farther west over the Bocky Moun-
tain region, there are red sandstone strata of great extent,
often containing gypsum, but generally without fossils, that are
regarded as Triassic. Fossils have been found in rocks of this
period in California, and also in British Columbia and Alaska.
Jurassic beds, with marine fossils, overlie the Triassic of the
Eocky Mountain region, west of the summit, making in part
the Wahsatch Mountains, the Sierra Nevada, and other ranges.
At the close of the Jurassic period a great geographical
change took place in Eastern North America and also west of
the Mississippi; for in the Cretaceous period beds full of
marine fossils were forming all along the Atlantic border
south of New York, and over a wide region bordering the
Gulf of Mexico; up the Mississippi valley, to the mouth of
the Ohio; from Texas northward over Kansas and a large
part of the eastern slope and summit region of the Eocky
Mountains, perhaps reaching to the Arctic; and also along
the Pacific border west of the Sierra Nevada. The outline
of the continent when these beds were in progress is shown
in the accompanying map (Fig. 182), the shaded portion be-
ing the part that was then under water, filled with Cretaceous
life and receiving Cretaceous deposits of sediment.
The Cretaceous beds are mostly soft green and gray sand-
stones, partly compact shell-beds and " rotten " limestone,
with hard limestone in Texas, and chalk in Western Kansas.
Marine fossils are abundant, and they generally indicate shallow
REPTILIAN AGE.
177
waters. Over the Bocky Mountain region the beds are in some
places 10,000 feet above the sea; showing that the mountains/
-p ^ |H*
have been elevated to this extent since the beds were made. '
Fig. 182.
North America in the Cretaceous Period.
MO, Upper Missouri region.
In Great Britain the Triassic beds (No. 6 on the accom-
panying map, Fig. 183) were red argillaceous sandstones and
clay rocks (marlytes) formed in a partly confined sea-basin. At
Cheshire they contain a bed of rock-salt derived from the evapo-
ration of the waters of the sea-basin. The Jurassic rocks con-
sist^ below, of a limestone called the Lias (No. 7 a) ; other
8* L
178
MESOZOIC TIME.
Fig. 183.
Geological Map of England.
The areas lined horizontally and numbered i are Silurian. Those lined vertically (2), Devonian. Those
cross-lined (3), Subcarboniferous. Carboniferous (4), black. Permian (5). Those lined obliquely from
right to left, Triassic (6), Lias (7 a), Oolyte (7 6), Wealden (8), Cretaceous (9). Those lined obliquely from
left to right (10, n), Tertiary. A is London ; B, Liverpool ; C, Manchester ; D, Newcastle.
limestones above called Oolyte (7 b), part of which is a
REPTILIAN AGE.
179
coral-reef limestone, showing that there were coral-reefs in the
British seas of the era ; and near and at the top of the series,
fresh-water or soil beds, called the Portland dirt-bed, and the
Wealden (No. 8). The oolyte is so named from the occur-
rence of beds of limestone which are made of minute spheri-
cal concretionary grains, of the size of the roe of a small .
fish, the word coming from the Greek for egg.
As the Jurassic ended there were large areas of dry land and
marshes in Southeastern England. But with the commence-
ment of the Cretaceous period there was a new submergence,
and green and gray sand-beds were accumulated, followed by
a deeper submergence and the formation of about 1,200 feet I
Figs. 184-187.
Rhizopods.
Fig. 184, Lituola nautiloidea ; 185, Flabellina rugosa ; 186, Chrysalidina gradata ; 188, Cuneolina pavonia.
of chalk, the upperjart containing flint nodules. The chalk \
consists very largely of the shells of Ehizopods, species not
larger than fine grains of sand, some of which are here fig-
ured, much enlarged; and since, as stated on page 34, similar
beds of Rhizopods are now in progress over the bottom of
the Atlantic west of Ireland, and the Sponges and some other
fossils of the chalk are probably deep-water species, it is be-
180
MESOZOIC TIME.
lieved that the chalk was formed at depths not less than
1,000 feet. The flint of the chalk was made from the sili-
ceous Sponges, spicules of Sponges, and Diatoms of the same
sea-bottom.
2. Life.
L Plants, The forests of Mesozoic time contained Conifers
and Tree-Ferns, like the Carboniferous, but were especially
Fig. 188.
Cycas circinalis (X
characterized by Cycads, plants that looked like Palms, as
the figure on page 180 shows, but were Gymnosperms, like
-REPTILIAN AGE.
181
the Conifers. Hence the forests of the early and middle
Mesozoic consisted chiefly of Tree-ferns, Conifers, and Cycads ; \
and where the Tree-ferns and Cycads predominated the aspect j)
was much like that of modern groves of Palms.
189-192.
Angiosperms (or Dicotyledons).
Fig. 189, Leguminosites Marcouanus ; 190, Sassafras Cretaceum ; 191, Liriodendron Meekii ; 192, Salix Meekii.
In the Cretaceous beds occur the first evidence of the ex-
istence, in the world, of actual Palms and of plants and trees
now so common, related to the Elm, Maple, and other trees
with net-veined leaves, species which have the seeds in a
seed-vessel, and which are therefore called Angiosperms, from
182
MESOZOIC TIME.
the Greek for vessel and seed. A few leaves from the Creta-
ceous of the United States are represented in Pigs. 189 to 192.
The forests still had in some places their numerous Cycads;
but their general character was changed, and for the first time
they looked modern.
2. Animals. The Corals and other Radiates had for the
most part a general resemblance to those of the present era,
although all were extinct and mostly of extinct genera. The
same is true of the Mollusks, and yet some kinds under these
classes were especially Mesozoic in type.
This is eminently true of the higher division of Mollusks,
the Cephalopods. The chambered shells of this tribe, repre-
sented by Orthocerata, Nautili, and
some related species in the Silurian,
were in vast numbers under the
type of Ammonites, while there were
also many Nautili. Fig. 193 repre-
sents a front view and 194 a side
_., _ . , , view of one of the earlier of these
V J Ammonites, a Triassic species.
The animal occupied the outer cham-
ber of the shell, as in the Nauti-
lus (Fig. 110, page 123). Fig. 193
shows the partition which was the bottom of this outer cham-
ber. Around its sides there are pocket-like depressions into
which the mantle of the animal descended to enable it to hold
Figs. 193, 194.
Cephalopod.
Fig. 193, Ammonites tornatus ; 194, side view
of same reduced to one half.
REPTILIAN AGE.
183
on to its shell. Two other species of Ammonites are repre-
sented in Eigs. 195 - 197. Fig. 196 shows the pockets in the
outer chamber of 195. Pig. 197 represents a species with the
outer edge unbroken and much prolonged. The pockets are
depressions in the partitions at their margins. There were
some Devonian and Carboniferous species, called Goniatitet, that
Figs. 195 - 197.
1 9 6
Cephalopoda.
Fig. 195, Ammonites Bucklandi, from the Lias ; 196, same in profile, showing outer chamber and its pockets ;
197, A. Jason, from the OSlyte.
had such pockets, but the pockets were simple in outline;
those of the Ammonites are very irregularly plicated within.
Their complicated outline is well shown in Fig. 198, repre-
senting the series along half the margin of a partition in a
Cretaceous species, the shaded part a to 6 being half of the
series of pockets, twice the natural size, and b 6 the middle
184 MESOZOIC TIME.
r line of the back of the shell. Among the Ammonites of
** \ the Cretaceous there were species four feet in diameter.
Fig. 198.
Series of pockets in Ammonites placenta.
Besides these there were other kinds of Cephalopods having
internal shells or bones and called Belemnites. One of these,
from the Cretaceous of New Jersey, is represented in Fig. 199,
but, as usual with the fossils, it is imperfect, the upper slen-
der part being broken off. Pig. 200 shows a side view of
the bone complete, as it has been found in some species.
The bone has the same relation to the animal as the pen
(Fig. 202) in the modern Squid (Fig. 201), it being internal
and lying in the mantle along the back; the animal of the
Belemnite was much like a Squid.
These Cephalopods were in great numbers in the seas, over
a thousand species having been found fossil. In view of
their abundance it is a remarkable fact that no Belemnite
and only one Ammonite is known to have lived after the
close of the Cretaceous, and we have no evidence that by the
close of the first period of the Tertiary even one was living.
These highest of Mollusks ' thus passed their climax during
the Mesozoic era.
REPTILIAN AGE.
185
The Vertebrates included not only Fishes and Beptiles, like
the Carboniferous age, but also Birds and Mammals.
Figs. 199-202.
Cephalopoda.
Fig. 199, Belemnitella mucronata, broken at top ; 200, a Belemnite with the upper part, a b, perfect ; 201,
modern Calamary or squid, Loligo vulgaris ; 202, pen or internal bone of same.
Fishes. Ganoids and Sharks were the prevailing kinds of
the Mesozoic until the Cretaceous era, and then fishes of
modern type Herring, Salmon, Perch, and the like were in
186 MESOZOIC TIME.
great numbers, species that have lony and not cartilaginous
skeletons, and which are therefore called Teliosts, meaning
bony throughout. They include the common edible species.
The Ganoids lost their tails, that is, the vertebrated char-
acter of the tail-fin, in the first period of the Mesozoic. Some
species had then a vertebrated tail, some half-vertebrated, and
others non- vertebrated, that is, had merely a caudal fin; but
after the Triassic, all were of the modern non-vertebrated type.
Reptiles. Eeptiles were the dominant species of the era
through all the periods.
In the Triassic, the Amphibians were of great size, as shown
by their footprints on the sandstones of the Connecticut val-
ley and at some other localities, and also by the bones that
have occasionally been found. Some of the largest of them
walked as bipeds on feet that made tracks 16 to 20 inches
long and nearly as broad, and with a stride of three feet,
indicating a height of at least 10 or 12 feet. Pig. 203
shows the form of the impressions. The tracks of the much
smaller forefeet are occasionally found, showing that this huge
biped Amphibian sometimes brought them to the ground; the
form is shown in Pig. 203 a. Twenty -two consecutive tracks
of one of these bipeds were laid open in 1874 at one of the
quarries of Portland, Connecticut. Other species have smaller
tracks, and some are less than half^an inch long.
Other Amphibians of the era walked on all fours. Pigs.
204, 204 a represent the tracks of a hind foot and fore foot
REPTILIAN AGE.
187
of one kind, and 205, 205 a those of another, both from the
Connecticut valley.
Figs. 203-206.
206*
Tracks of Amphibians and True Reptiles.
Amphibians : Figs. 203, 203 a, Otozoum Moodii (X /') ; 204, 204 a, Anisopus Dewyanus ( X %) ; 205, 205 a,
A. gracilis ( X %). True Reptile: Fig. 206, 206 a, Anomcepus scampus, a Dinosaur ( X J4).
All the Amphibians, there is reason to believe, had large
teeth and scale-covered bodies, like the Amphibians of the]
Carboniferous age. A tooth of a related four-footed species
from Europe is shown two thirds the natural size in Pig.
207. The head of the Amphibian that was thus armed was ;
over 2 feet long, and three fourths as broad.
There were also true Eeptiles of various kinds. One division
of them, called Dinosaurs (meaning terrible lizards), had the
hinder feet three-toed like those of birds. The tracks of one
from the Connecticut valley sandstone is shown one-sixth the
natural size in Eig. 206. They .walked usually on their hind
188 MESOZOIC TIME.
legs, like bipeds, but sometimes put their forefeet down. These
were four-toed. The print of the forefoot of this species is
represented in Fig. 206 a.
Fig. 207. There are many kinds of three-toed tracks in
the Connecticut valley sandstone which have
never been found associated with tracks of the
forefeet; and as they have precisely the form
of those of birds, they have been regarded bird-
tracks. But they may have been all made by
these bird-like Eeptiles.
Some of the Dinosaurs of the Jurassic and
Cretaceous periods better deserve the name of
saurus. terrible lizards. The Megalosaur was a huge
carnivorous reptile 25 to 30 feet long; the Iguanodon and
Hadrosaurs were vegetable eaters, fully as large.
Another division included Enaliosaurs, or the Sea-Saurians,
which had paddles like whales, and were 12 to 50 feet long.
Fig. 208.
Ichthyosaurus communis ( X /, o)-
a, one of the vertebrae.
One kind, called Iclithyosaurs (meaning fish-lizards] (Fig. 208),
had a short neck, a very large eye, and thin vertebrae concave
REPTILIAN AGE. 189
on both sides (Fig 208 a), much resembling those of fishes.
One species was 30 feet long. Another kind, called Plesiosaurs
(meaning, somewhat like a lizar d), had a long snake-like neck
(Fig. 209), short body, and vertebrae as long as broad.
Fig. 209.
Plesiosaurus dolichodeirus ( x J6 ).
a, one of the vertebrae ; b, profile of same.
A third division included the Mosasaurs, snake-like rep-
tiles, 15 to 80 feet long, with short paddles, jaws sometimes
a yard long, and the lower jaw peculiar in having an elbow-
joint to fit it to be used like an arm for working the carcass >
of a great beast down its enormous throat. They had power-
ful teeth; one of them, about half the size of the largest, is
represented in Fig. 210. Several species have been found in
the Cretaceous beds of New Jersey and Kansas, along with
Hadrosaurs, Dinosaurs, and other kinds.
A fourth division included Crocodiles, with long slender jaws
like the Gavial, the crocodile of the Ganges.
190
MESOZOIC TIME.
Fig. 210.
A. ^h division included flying Beptiles,
called Pterosaurs (from the Greek for winged
Saurian). One of them, reduced to one
fourth the natural size, is represented in Fig.
211. The wing is made by the elongation
of one of the fingers and the expansion of
the skin from the side of the body. Some
species from Kansas had an expanse of wing
of 24 or 25 feet. They had the habits of "]
bats.
Thus the age was literally an age of
Beptiles. Air, earth, and seas were all occu-
pied by them, and by species of great mag-
nitude, among them those of the highest
grade. The Eeptilian type thus had its
maximum display in Mesozoic time.
Birds. A bird with its feathers has been found fossil in
the Oolyte of Solenhofen, Germany; and bones of a number
of birds in the Cretaceous of the United States. The Solen-
hofen bird had a long tail, furnished with a row of long quills
either side. A Kansas species, described by Professor Marsh,
had teeth set in sockets, a striking Eeptilian character.
Mammals. Bones from a few species of Mammals have
been found, the earliest in the Triassic beds of Germany and
North Carolina. Fig. 212 represents a jaw-bone from North
Carolina. The remains of other related kinds have been found
Tooth of a Mosasaur.
REPTILIAN AGE. 191
in the Oolyte at Stonesfield, England, and also in the Upper
Oolyte in the Purbeck beds. The species are Marsupials,
Fig. 211.
Pterosaur.
Fig. 211, Pterodactylus crassirostris (X #).
that is, mammals related to the Opossum and Kangaroo; they
are peculiar in having a pouch (Marsupium, in Latin) on the
under side of the body, over the breast of the mother, for
Fig. 212.
Dromatherium sylvcstre.
receiving the young, which are born in an immature state.
Nearly all modern Marsupials are confined to the continent of
Australia; a few exist still in America.
192 MESOZOIC TIME.
Thus all the classes of Yertebrates had, in Mesozoic time,
their species, even to Birds and Mammals. As early as the
/ Triassic, its first period, the Amphibians passed their climax
\ in numbers, size, and grade, little being afterward known of
nhe huge scale-covered tribe ; and during its following periods
true Reptiles had their time of greatest expansion, giving a
strong Reptilian character to the Reptilian age. But the
Birds and Mammals which appeared in the age were only the
commencement of tribes that were to reach their fullest dis-
play in later time. Both the early Birds and Mammals had
marks of inferiority, and also characteristics that showed some
relation to the Reptiles with which they lived. Thus the
Birds had long tails, and some, at least, true teeth like Rep-
tiles ; and the Mammals have been called semi-oviparous, that
is, kinds whose young were in an immature state when born,
approximating in this respect to the egg state, which is an
example of an extreme degree of immaturity. It is also a
fact of interest that among Reptiles the Dinosaurs were like
birds, not only in their biped mode of locomotion, but in the
special way by which they were adapted to this kind of pro-
gression ; for they had the same kind of feet as birds, the
same number of toes, the same number of joints to the sev-
eral toes, also hollow bones in part, a somewhat similar
structure in the hinder part of the skeleton to which the leg-
^ bones are articulated, and other points of resemblance.
The progress in the life of the world in Mesozoic time is
REPTILIAN AGE. 193
also seen in the fact, that with the opening of its third period,
Sharks and Ganoids were no longer the only fishes, the mod-
ern tribes having made their appearance; and, too, Conifers,
Tree-ferns, and Cycads were not the only forest-trees, for al-
ready Palms and Aagbspesas had added vastly to the variety fix
of foliage and to the richness of the flowers and fruits. Of
lines of transition from the older trees up to these Palms and
AngiagpfTTVi" nothing is known. ^
The old law of change characterized the life of Mesozoic
time. New fossils are found in every successive rock-stratum,
and also older kinds are missed. The system of life was in
course of expansion by the introduction of new species and a
casting off of the old.
3. Mountain-making in Mesozoic Time.
The Sierra Nevada, Wahsatch, and some other ranges of [
the western slope of the Eocky Mountains were made at the
close of the Jurassic. All the strata there existing from the
bottom of the Silurian to the top of the Jurassic were folded)
up in the making of the Wahsatch Mountains, and probably )
in that of the Sierra Nevada.
In the course of the Jurassic, or at its close, the Triassic
(or Triassic and Jurassic) rocks of the Atlantic border (Con-
necticut Eiver valley and elsewhere) were slowly tilted; and
then occurred a great number of deep fractures, mostly par-
allel in course to the direction of the areas of the sandstone,
9 M
194 CENOZOIC TIME.
which opened down to a region of liquid rock; for the liquid
rock came to the surface and cooled, and now constitutes
many ridges, such as Mount Holyoke, Mount Tom, the Pali-
sades on the Hudson, and others between Nova Scotia on
the north and South Carolina. During the formation of the
sandstone a slow sinking was in progress, as is proved by the
footprints on the surfaces of layers and other markings, these
showing that the layers originally mud-flats and sand-flats
of an estuary were successively at the water-level. The
sinking brought a strain on the rock-made bottom of the
trough, and ended in a breaking of the crust, and thence
came the ejections of trap. The trap resembles the cooled
rock of most volcanoes, but is commonly much more compact.
IV. Oenozoic Time.
CENOZOIC TIME comprises two Ages :
I. The TERTIARY, or AGE OF MAMMALS.
II. The QUATERNARY, OT AGE OF MAN.
I. The Tertiary, or Age of Mammals.
The Tertiary age has been divided into three sections: (1)
the EOCENE; (2) the MIOCENE; (3) the PLIOCENE. These
terms signify, severally, (1) the dawn of recent time; (2) the
less recent ; (3) the more recent. The areas of Tertiary rocks
in North America and England are distinguished on the maps,
TERTIARY AGE.
195
pages 105 and 114, by being lined from the left above to
to the right below.
1. Rocks.
In the accompanying map the white area represents the
dry land of the continent in the Eocene, or early part of the
Fig. 213.
Hap of North America in the early part of the Tertiary Period.
Tertiary. Only the borders of the Atlantic, the Gulf of
Mexico, and the Pacific (the shaded portions) were covered
by the sea, and over these parts Tertiary rocks were forming
through marine action aided by the contributions of rivers.
196 CENOZOIC TIME.
The geographical changes since the opening of the Creta-
ceous period were great, as will be seen by comparing the
map with that on page 177. The Eocky Mountain region
was now above the sea. The rivers of the eastern part of
the continent, or those contributing waters and sediment to
the Atlantic, had two thirds or more of their present extent;
but the Ohio and Mississippi were still independent streams,
emptying together into an arm of the Mexican Gulf. The
Missouri and other western streams were just beginning to
be. The Mountain region but slowly emerged, and till near
the close of the Tertiary there were great lakes instead of
great rivers. In the Eocene the lakes occupied the Green
River and other summit basins. Afterward they were farther
east and west, and in the Pliocene, as Marsh states, a lake
extended from Northern Nebraska to Texas. The Tertiary
consequently includes, from its beginning, vast fresh-water as
well as marine formations.
Marine Tertiary beds of the Eocene period were formed on
the Atlantic border south of New York, and on the borders
of the Mexican Gulf; but Miocene only on the Atlantic bor-
| der, some change of level having excluded them from the
Gulf border west of Florida; and Pliocene along the coast
-^( region of South Carolina, though of this there is doubt. On
the Pacific border there- are marine beds, both of the Eocene
and Miocene periods; the latter are most extensive.
Underneath the Marine Eocene beds of the Lower Mississippi
TERTIARY AGE. 197
there are Lignitic beds, that is, beds containing lignite
a kind of mineral coal retaining usually something of the
structure of the original wood alternating with beds that
are partly marine, the whole indicating that fresh-water marshes
there alternated with fresh- water lakes and salt seas ; for the
Lignitic beds were once beds of vegetable debris such as are
formed in marshes.
Fresh-water Tertiary beds cover large areas over the Eocky
Mountain summit region, and its eastern slope, as well as
part of its western in Oregon and elsewhere. They were
formed in and about the great lakes alluded to above. Im-
mense numbers of bones of mammals and many entire skele-
tons are contained in these beds, showing that the shores of
these lakes were the resort of wild beasts, some of them of
elephantine size. In the Green River basin and other parts
of the summit region the beds are Eocene; while over the
eastern slope they are mostly Miocene and Pliocene, the
latter of widest extent.
Underneath these fresh-water beds over the eastern slope
in the region of the Upper Missouri, and far north in British
America, as well as far south, there is a Lignitic formation
which is partly, especially below, of brackish- water origin;
and these are equivalents of the Lignitic beds below the
marine Eocene of Mississippi. Over the summit region of
the mountains the Lignitic formation has a thickness of sev-
eral thousand feet, and instead of Lignitic beds there are val-
198 CENOZOIC TIME.
uable beds of mineral coal. There are marine, brackish-water,
; and fresh-water strata in the formation, the latter mainly in
the upper part. The coal-beds occur in Wyoming, Utah, and
Colorado, and some of them, opened near the Pacific Bailroad,
afford coal for its locomotives. These beds overlie the Cre-
taceous beds conformably, and the latter also have similar coal-
beds; so that the Cretaceous deposits and era here blend with
the Tertiary. Moreover, a very few Cretaceous shells occur in
some of the marine beds and the remains of some reptiles
related to the Cretaceous Dinosaurs. The great majority of
the fossils are Tertiary in aspect and genera, and they are
therefore here referred to the Eocene, although regarded as
Cretaceous by some geologists. These Lignitic beds and the
. underlying Cretaceous were all upturned together in one
- / mountain-making effort, before the fresh-water Eocene
A"
i of the Green Eiver basin were deposited.
In Great Britain there are marine Eocene Tertiary beds in
the " London basin," and next a thin Pliocene stratum, no ma-
rine Miocene existing there. Over Europe and Asia the Eocene
formation was widely distributed, showing that those continents,
even as late as the early Tertiary, were largely under the
sea. The Pyrenees, portions of the Alps, Apennines, Carpa-
thians, and mountains in Asia were partly made of them.
The beds in many places contain the coin-shaped foraminifers
(Ehizopod shells) called Nummulites, varying from half an
inch to one inch or more in diameter; and the limestone of
TERTIARY AGE. 199
which some of the Egyptian pyramids are built is made up
chiefly of Nummulites. One of them is shown in Fig. 214;
the exterior is represented as removed from part Figt
of the interior to show the cells, which were once
occupied by the minute BMzopods. Some species
of a related genus occur in modern coral seas.
They must have been exceedingly abundant over
the great continental seas of the Tertiary. Miocene beds have
a thickness of several thousand feet in Switzerland (consti-
tuting the Eigi and some other summits), and occur in many (
other parts of Europe; but they are limited in area com- }
pared with the Eocene. Marine Pliocene beds are of still
less extent, yet have a thickness in Sicily of 3,000 feet.
The marine Tertiary rocks are very various in kind. The
larger part are soft sand-beds, clay-beds, and shell deposits,
the shells often looking nearly as fresh as those of a mod-
ern beach. Others are moderately firm sandstone. There
are also loose and firm limestones. The green sand called*
"marl/'' used as a fertilizer, which is so characteristic of^
the Cretaceous, also constitutes beds in the Tertiary of New
Jersey.
The fresh-water beds are like the softer marine beds,
but contain, of course, no marine shells. Part of them are
quite firm; but others are easily worn by the rains. Some
great areas in the Eocky Mountain region, both over the
summit and the eastern slope, have been reduced in this way
200 CENOZOIC TIME.
to areas of isolated ridges, towers, pinnacles, and table-topped
hills, that are mostly barren, owing to the dry climate, and
which are therefore called " Bad Lands," or in French (in
which language the expression was first applied), " Mauvaises
Terres."
2. Life.
The life of the Tertiary age shows in all its tribes an ap-
proximation to that of the present time. The mammals, and
probably the birds, are all of extinct species. But among
the plants and the lower orders of animals there were many
species that still exist : in the Eocene, a small percentage ; in
the Miocene, 25 to 40 per cent; and in the Pliocene, a much
larger proportion. The common oyster and clam were living
as far back as the Miocene era, along with a large number
of shells that are now extinct species. Progress through the
Tertiary era was gradual in all departments.
The forests of North America were much like the modern,
but with a larger proportion of warm-climate forms. Palms
flourished over Europe and in England through the Eocene.
In the Miocene the European species were still those of a
warmer climate than the present, and included some Australian
species. Even in the Arctic zone there were in the Miocene
great forests of Beach, Oak, Poplars, Walnut, and Redwood
(Sequoia, the genus to which the " great trees " of California
belong), with Magnolias, Alders, and others.
The modern aspect of the marine shells is shown in the
TERTIARY AGE.
201
following figures : Figs. 215 - 219, of American Eocene spe-
cies, and 220 - 223, of Miocene from the Atlantic border.
Figs. 215-219.
Eocene of Alabama.
Fig. 215, Ostrea sellaeformis ; 216, Crassatella alta ; 217, Astarte Conradi ; 218, Cardita planicosta ; 219,
Turritella carinata.
This is further manifest in the following figures of fresh-water
shells from the Lignitic beds of the Rocky Mountain regions,
Figs. 220-223.
222
Miocene of Virginia.
Figs. 220, 221, Crepidula costata ; 222, Yoldia limatula ; 223, Callista Sayana.
9*
202
CENOZOIC TIME.
species which are supposed to prove that those beds are
Tertiary instead of Cretaceous. To appreciate the change since
Fig. 230.
Shells of the Lignitic Beds.
Lamellibranchs : Figs. 224, 224 a, Corbula mactriformis ; 225, Cyrene intermedia ; 226, Unio priscus.
Gasteropoda : Fig. 227, Viviparus retusus ; 228, Melania Nebrascensis ; 229, Viviparus Leai.
Paleozoic time, the reader should turn back to the figures of
shells on pages 121 to 133.
The Tertiary Vertebrates were more unlike the moderns
than- the Invertebrates. Among
fishes, Sharks were exceedingly
abundant, and their teeth, the most
enduring part of the skeleton, are
very common in some of the beds;
and those of one kind, pointed, tri-
angular in form, were nearly as
large as a man's hand. One of
the smaller of these teeth is repre-
sented in Fig. 230.
The true Eeptiles were Crocodiles,
Lizards, Snakes, gigantic and smaller Turtles, and others.
Shark's tooth.
Carcharodon angustidens.
TERTIARY AGE.
203
Among the birds there were Owls, Woodpeckers, Cormo-
rants, Eagles; and those of France included Parrots, Trogons,
Flamingoes, Cranes, Pelicans, Ibises, and other kinds related
to those of warm climates.
The Mammals of Mesozoic time, thus far discovered, were
probably all of the lower order called Marsupials; but with
the opening of the Cenozoic era there were true Mammals.
The Eocene beds about Paris, France, afforded to Cuvier the
first specimens described ; and now they are known from all
parts of the world, and from none in greater variety than from
the fresh-water Tertiary region west of the Mississippi.
The earliest kinds were related most nearly to the mod-
Fig. 281.
Tapirus Indicus, the modern Tapir of India.
ern Tapir (Fig. 231), Hog, Ehinoceros, and Hippopotamus.
There were also kinds between these and the Deer. All the
above mentioned are Herbivores, that is, plant-eaters. There
204
CENOZOIC TIME.
were also Carnivores, or flesh-eaters, related to the dog and
wolf, and Monkeys related to the Lemurs.
One of the Herbivores of the Bocky Mountain Eocene is
the Dinoceras of Marsh, a figure of the skull of which is
here given. It was nearly as large as an Elephant, but had
Fig. 232.
Dinoceras mirabile (X %).
six horns and was somewhat related to the Ehinoceros. Fig.
233 represents the skull of one of the Miocene species,
an Oreodon, which was intermediate in characters between
/ the Deer, Camel, and Hog. The form of a European spe-
cies more like a Deer, called a XijpJwdon, is given, as re-
stored by Cuvier, in Fig. 234. There were also Horses
through the Tertiary; but while the modern Horse has only
TERTIARY AGE.
205
one toe out of the full mammalian number five, some of the
Pliocene had three toes, one large, and two too short for use;
Fig. 233.
Oreodon gracilis.
Miocene kinds had three toes, and all usable; and the Eocene
had four toes, and all usable.
Fig. 234.
Xiphodon gracile.
206 CENOZOIC TIME.
In the Miocene and Pliocene there were Mastodons, Ele-
phants, Bhinoceroses, Camels, and Monkeys over the Bocky
Mountain region, besides many smaller species. The marine
Tertiary of the Atlantic border has afforded, as should be
r expected, but few of these species. Cattle related to the Ox
have not been found in beds earlier than the Pliocene.
The Mammalian type was at last extensively unfolded, its
grand divisions being well represented. But the maximum
, / display of the brute races took place still later, in the early
\ or middle Quaternary, after Man had appeared.
3. Mountain-making.
/ In North America, after the deposition of the coal (or Lig-
) nitic) beds of the summit region of the Bocky Mountains,
{ / and of similar beds in California, there was a flexing and
/ upturning of the strata along with those of the Cretaceous
' beneath, which together, as has been stated, make one con-
) tinuous series, and ridges over 3,000 feet and more high
V were thus made in the coast region of California, and others
of greater height in Mexico, New Mexico, Colorado, and to
the north.
During the formation of the Lignitic beds the uplifting of
the whole Bocky Mountain region above the sea was in pro-
gress; for such beds of vegetable debris as they were made
from show that long periods of rest above the sea alternated
with shorter periods of submergence. After the epoch of up-
TERTIARY AGE. 207
turning which followed, if not also contemporaneously with
it, this elevation was continued, and without a return again
below the sea-level. But the existence of the vast fresh-water
lakes over the surface proves, as first observed by Hayden,
that the rising went forward with extreme slowness, and
probably with long delays at intervals; and it is quite cer-
tain that the present height at least 10,000 feet in Colo-
rado and Wyoming above the level in Cretaceous times, since
the Cretaceous beds, full of marine fossils, are now at this
height was not attained before the close of the Pliocene,
if it was then.
The Pyrenees, Apennines, part of the Northern Alps, and
other high mountains of Switzerland, the Carpathians, and
other mountains in Eastern Europe were raised thousands of
feet, and the mountain regions in Western Thibet, in Asia,
16,500 feet, after the Eocene Tertiary had partly passed, and
the rise perhaps began at the same time with that of the ^
Cretaceous and Lignitic mountains of the Rocky Mountain
summit and the coast region of California.
After the Miocene another range 2,000 to 3,000 feet in
height was made along the California coast-region west of the
Cretaceous range, and some disturbances took place in the
Tertiary over the summit region of the Rocky Mountains.
The close of the Miocene was a time of great disturbance
and of mountain-making also in Europe, to the north of the j
Alps, in Switzerland, and elsewhere.
208 CENOZOIC TIME.
At the same time, that is, in the Miocene era, great erup-
tions of igneous rocks took place over the western slope of
the Rocky Mountains, covering thousands of square miles;
^-.^ and probably the deep fractures were then opened which gave
/ origin to the volcanoes Mount Shasta, Mount Hood, and other
summits in the Cascade Range. So also along the coast of
( Ireland and of Scotland, and the Inner Hebrides to the Faroe
/ Islands, the eruptions were of great extent. Fingal's Cave and
S the Giant' s Causeway date from this period.
In each case over the Rocky Mountains the making of a
mountain range was preceded, as in that of the Appalachian
region (page 168), by a sinking of the earth's crust where the
range was to be, and the accumulation in the trough, as it
formed, of some thousands of feet of deposits. Then followed
the catastrophe, as explained for the Appalachian region on
page 172, causing upturnings, foldings, fractures, consolida-
tion; and sometimes also a crystallization of the beds, chang-
ing them to granite, gneiss, and allied rocks. Each time, after
a mountain system was completed, that part of the earth's
crust was too much stiffened to be the site of another sink-
ing trough, and consequently the trough made later, if there
was any so made, was to one side of the former. In the
Tertiary the crust over the whole Rocky Mountain region had
finally become so stiffened that no new trough was begun
after the Miocene; and instead of a folding of the thick Mio-
cene formation into a mountain range, great breaks of the
QUATERNARY AGE. 209
crust took place from which floods of lavas were let loose and
the lofty volcanoes were begun.
4. Climate.
During Mesozoic time the Arctic zone was warm enough
for great Reptiles, warm-climate species, and the British
seas for coral-reefs.
The close of the Cretaceous was probably an era of unusual-
cold, sending cold oceanic currents from the Arctic zone; for
no other cause will account for the general destruction of spe-
cies that then took place over the continental seas of America,
Europe, and Asia. But the Eocene era was one of warm
climate again over Great Britain, for England was then a
land of Palms; and Palms continued to flourish over Middle
and Southern Europe during the Miocene period. Through
both the Eocene and Miocene the Arctic lands were covered
with forests, and hence the Arctic climate must have been
comparatively warm, not colder at least than the presents
climate of the Middle United States- and Northern Prussia.]'
There was a cooling off with the progress of the Miocene,
and by the close of the Tertiary the earth had probably its j
frigid, temperate, and torrid zones, nearly as now.
2. Quaternary Age, or Era of Man.
The scene of work for the Quaternary age was to a large
extent widely different from that of the Tertiary and preceding
210 CENOZOIC TIME.
ages; and the kind of work was equally different. With the
close of the Tertiary the continent, which was begun in the
nucleal V of Archsean time, was finished out very nearly to
its present limits, and at its close an elevation added the Ter-
tiary formation of the sea-border to the dry land.
This accomplished, the Quaternary opened. Agencies were
now at work over the broad surface of the continent its
dry land, and not continental seas, as formerly transport-
ing southward gravel and earth from regions to the north, in
order to cover the hills with gravel and soil and fill the val-
leys with alluvial plains. Over both Europe and America
transportation went forward from the high latitudes southward,
except where there were mountains sufficiently lofty to be
sources of independent movements. Hills and valleys were
no impediment to the great agent engaged in this immense
continental system of transportation. The aid of the ocean
was not needed in these movements, and was not given ex-
cept to a small extent along its borders.
After these great results were attained the work of the
rivers went on more quietly, and finally, through this and
other agencies, in connection with some change of continental
level, the earth assumed slowly its present perfected condition
of surface and climate.
The age is divided into three periods : (1) the GLACIAL
period; (2) the CHAMPLAIN period; (3) the BECENT or TEE-
RACE period.
QUATERNARY AGE. GLACIAL PERIOD.
1. Glacial Period.
1. Glacial Phenomena. The general facts are these:
In America and Europe, over the northern latitudes, sand,
gravel, stones, and masses of rock hundreds of tons in weight
are found from a few miles to a hundred and more south of
the region whence they were derived. This transported ma-
terial is called drift, and the stones or rocks, bowlders.
In North America, the region over which the transportation
took place embraced the whole surface from Labrador or
Newfoundland to the western borders of Iowa, and farther
west for a distance not yet determined, and it reached south-
ward to the parallel of 40 and in some places beyond this.
In Europe it included the British Islands and Northern Eu-
rope, down to the parallel of 50, where the temperature is
about the same as along the parallel of 40 in North America.
The direction of travel was generally to the southeastward,
southward, or southwestward.
- The fact and the direction of transportation have been as-
certained by tracing the stones to the ledges from which they
were derived. Thus bowlders of trap and red sandstone from \
i
the Connecticut valley are found on Long Island, and masses 5
of granite, gneiss, quartzyte, and other rocks in New Eng- <
land, to the southward or southeastward of the ledges that >
afforded them. In the same manner masses of granular mar-
ble have been proved to have come from a formation 50 or 7
212
CENOZOIC TIME.
100 miles to the northward of their present position. So
again masses of native copper are found in Indiana and Illi-
nois that were brought from the veins of native copper south
of Lake Superior. The greatest distance to which bowlders
have been traced has been 400 or 500 miles in Europe, 200
or 300 over Eastern North America, and 1,000 miles along the
Mississippi Eiver valley, where they reach nearly to the Gulf.
The masses sometimes contain 2,000 to 3,000 cubic feet,
so that they compare well in size with large houses.
Drift regions are also regions of extensive planings, pol-
ishings, and scratchings of the rocks (Fig. 235). These
Fig. 235.
Drift scratches and planings.
scratches may almost anywhere be found on rocks that have
been recently uncovered. Yast areas are thus scoured and
scratched over, and the scratches have great uniformity in
direction. The bowlders also are scratched.
QUATERNARY AGE. GLACIAL PERIOD. 213
Scratches and bowlders occur on top of Mount Mansfield,
the highest point in the Green Mountains, 4,430 feet above 1
the sea, and at a level of 5,500 feet on the White Mountains 5
in New Hampshire; and the direction of the scratches shows
that the transporting agent moved over both of these sum- .
mits without finding in them any serious impediment, and M-
thence continued on its way southeastward.
The drift covers the mountains and hills of drift regions,
and makes also a large part of the formations in the valleys.
Over the hills it is unstratified drift) the sands, gravel, and
stones having gone down pell-mell together ; in the ^valleys it ) ^
is stratified drift, stratified because there the sands and
gravel were deposited in flowing water, which sorted some-
what the material and spread it out in beds. The excava-
tions in cities or villages for the cellars of houses are often
made in the stratified drift, and the sands usually show a
succession of beds which is evidence of the action of water.
2. Cause of the Glacial Phenomena. No known agent is
adequate for transportation on so vast a scale excepting mov-
ing ice. And, as Agassiz was the first to appreciate, it was
glacier ice. The size of the blocks transported is no greater
than is now borne along on the backs of glaciers; and the
planing and scratching is just what the Alps everywhere ex-
emplifies. The moraines of the glaciers, as explained on page
60, are derived in the Alps from the cliffs either side of the
ice-stream, and a small part only are taken up by the abrad-
214 CENOZOIC TIME.
ing surface at bottom. In the Continental glacier of the Gla-
cial period, the stones, gravel, and sand were gathered from
the hills over which the ice moved, for there were no cliffs
or peaks projecting above the surface even in hilly New
England. The White Mountains, as above stated, have
scratches to a height of 5,500 feet, or to within 800 feet of
the summit, and therefore were buried in the great glacier
nearly to its top, and in snow, if not ice, for the rest. Tak-
I ing the height at the White Mountains as a guide, the upper
surface of the glacier at that point was at least 6,000 feet
above the sea-level, and the thickness of the mass about 5,000
feet. Prom this region it sloped away over Southern and
Southeastern New England to its place of discharge in the
Atlantic. A thickness of even 2,000 feet, which is over four
times that of the largest Alpine glacier, would have given great
abrading power to the heavy mass. All soft or decomposed
rocks would have been deeply worn away by it, and hard
rocks with open joints or planes of fracture torn to pieces;
and the heavily pressing, slowly moving mass would have taken
the loose and loosened rock-material over the hills beneath
into itself, as additional freight for transportation.
/ Masses of trap 500 to JLOOCLtons in weight lie along the
\ elevated western border of the plain of New Haven in Con-
necticut, which were gathered up from the trap hills between
Meriden and Mount Tom in Massachusetts. The hills are
1,000 to 1,300 feet high, and their tops, when the masses
QUATERNARY AGE. GLACIAL PERIOD. 215
were taken up, were 1,500 to 2,000 feet below the upper sur-
face of the overlying glacier.
A glacier moves in the direction of the slope of its upper (
surface, in spite of the slope of the surface beneath it. It
is like thick pitch in this respect. If pitch were dropped
indefinitely over a spot in a plain, it would spread away
indefinitely; and if the surface around had a rising slope, it
would fill up the basin and then keep on its course. So it
is with the ice of a glacier. In order to have a southeast-
ward course, a glacier must have its surface highest to the
northwestward with slope southeastward; and if the snows
were more abundant to the north in the Glacial era, and the
melting less abundant there, than to the south, an accumula-
tion to the north might have gone on that would have pro-
duced movement southward. If the plain beneath the pitch
had deep channels obliquely crossing it, the pitch in these
channels would follow their direction, while the overlying
pitch kept on its main course. So with the glacier : its lower
part within the large valleys followed the directions of the
valleys, as the scratches and bowlders show; while the upper
portion had its usual course, the course which is indicated
by the scratches elsewhere over the higher parts of the
country.
The cold of the era may have been mainly due to an ele-
vation and extension of Arctic lands, increasing the area of
Arctic land-ice; and to a partial closing, through this eleva-
216 CENOZOIC TIME.
tion, of the Arctic region against the warm current of the
Atlantic Ocean, the Gulf Stream, which is now a source of
warmth to all of Northeastern Europe, and even Iceland,
Nova Zembla, and the polar seas and lands. Other reasons
for cold have been suggested, references to which will be
found in large works on the subject.
South America has its Glacial region, and evidences of
transportation toward the equator; so that the phenomena
described were not confined to only one hemisphere. Some
writers suppose it to have been alternately in the two hemi-
spheres. But the evidence of this does not appear to be satis-
factory.
The moving glacier of New England appears to have had
its head in the height of land between the St. Lawrence val-
ley and Hudson Bay; for the scratches diverge from this
region over Eastern Maine, New Hampshire, Vermont, and
New York, being in "Western New York and the region just
east of Lake Huron southwest in direction.
South of drift latitudes there were glaciers of great magni-
tude about the higher mountains; and moraines, scratches,
roches moutonnees, occur on a grand scale in many valleys of
the higher ridges of the Eocky Mountains and the Sierra
Nevada, as mementos of their former Glacial history. The
accompanying sketch (Fig. 236) of roches moutonnees in one
of the higher valleys of Colorado is repeated here from page
61, because the events indicated belong to the Glacial period.
QUATERNARY AGE. GLACIAL PERIOD.
217
The roches moutonnees extend along the valley through an
ascent of nearly 2,000 feet. At present there are no glaciers
within 500 miles of the place.
Flar 230.
View on Roche-Moutonnee Creek, Colorado.
In the same era a glacier in the Alps buried all Switzer-
land 2,000 to 4,000 feet deep in ice, and left immense blocks >
of Alpine rocks on the Jura Mountains.
Depositions of earth and stones from the glacier must have
been going on to some extent through the whole Glacial era.
The perpetual grinding of stones against stones in a glacier makes
a very fine clayey earth ; and a clay of this kind was dropped
10
218 CENOZOIC TIME.
over the hills and in the valleys, making thick deposits; and
as these deposits often contain large bowlders, derived likewise
from the glacier, they are called bowlder-days.
2. Champlain Period.
1. Melting of the Glacier and Deposition of the Drift. The
larger part of the deposition of the drift was delayed until
the glacier melted. There is reason to believe that during
the Glacial period the land over the northern latitudes stood
at a higher level than now, and that this was one cause of
the occurrence of a cold era. Whether this were so or not,
the glacier was made finally to disappear through a sinking
of the land over northern latitudes, which brought on a
milder climate and determined, and then hastened, the melt-
ing. This subsidence marks off the commencement of the
Champlain period, the second period of the Quaternary. The
earlier part of it was the era of the melting of the great
glacier. The melting would have gone on for a long time
with extreme slowness ; but when the glacier was thinned
down to the last 500 to 1,000 feet, in which part of it the
most of the gravel and stones were, it went forward rapidly;
and then took place the pell-mell dumping of gravel and stones
over the hills and valleys, with the stratification of whatever
fell into the waters. At last, as the facts prove, there was an
immense flood owing to the rapidity of the final melting; for
the later depositions in many regions are greatly coarser than
QUATERNARY AGE. CHAMPLAIN PERIOD. 219
the earlier, the finer material having been swept away down
stream and into the ocean.
The Mississippi valley was the outlet for the waters of the
great region it now drains; and the flood during the whole
Glacial period must have been great, and floating ice laden
with northern stones must have often hurried off down stream
to the Gulf. But at the final flood it made thick deposits
on the way to the Gulf, as observed by Hilgard, and in
Mississippi bowlders as large as a bushel basket are found in
the beds.
Icebergs thus despatched to the Mexican Gulf must have
made havoc of the warm- water life; and it is therefore no
occasion for surprise, as Hilgard remarks, that the sea-shore
drift deposits contain no marine species of shells.
The subsidence, with which the Champlain period opened,
was greatest to the north, being over 500 feet on the St.
Lawrence near Montreal, 400 feet on Lake Champlain, over
200 feet on the shores of Maine, and but 40 to 100 feet along
Southern New England. The river-beds hence did not have
even their present slope, and consequently the rivers in part be-
came great lakes. For the same reason the flood waters made
deposits of great breadth along the river valleys and lake re-
gions, the greatest fresh- water deposits of geological history.
The depth of the submergence at Montreal, on Lake Cham-
plain, along the coast of Maine, and most other points on
the sea-coast is proved by the occurrence of sea-shore depos-
220 CENOZOIC TIME.
its full of sea-shells at the heights just stated. In the beds
on Lake Champlain the bones of a whale have been exhumed,
which lived in the waters of the lake in the Champlain pe-
riod, when it was a great arm of the enlarged St.- Lawrence
Gulf. All the rivers and lakes over the continent in the lati-
tudes north of 40, and partly those south of it, have high
alluvial plains at a level far above the river or lake they
border; and they were made in this Champlain period when
the land was below its present level.
2. Champlain Period after the melting. After the melting
was completed, the rivers, though still at flood height, were
more quiet in their action, and they made depositions in
the river- valleys, wherever these were not already filled to
the flood level, of a finer alluvium; and much of this allu-
vium contains fresh-water shells, and occasional bones of
quadrupeds. The amount of sand, gravel, and clay which
had been dropped over the hills by the ice was immense,
and it lay loose, easy to be taken up by streams the rains
might make; and hence the filling of the valleys even after
the ice had disappeared may have gone forward for a while
with much rapidity. But the finer alluvium shows that
before the Champlain period ended the flow of the larger
streams was comparatively quiet.
In Europe and Great Britain the Champlain period was one
of subsidence over the higher latitudes, as in America, and
the subsidence was greatest to the north. In Prance and
QUATERNARY AGE. RECENT PERIOD. 221
Belgium the depression below the present level was 50 to j (__
100 feet; in Southern England, 100 to 200 feet; in Northern
England and Scotland, as reported by British geologists, 1,000 (
to 1,400 feet. In Sweden it was 200 at the south to 400 or </
500 to the northeast, so great that an ocean channel then
connected the Baltic with the White Sea. The alluvial deposits
on the Rhine, below Basle, are in some places 800 feet or J
more in height above the river. But this height does not
indicate a depression of as great an amount in the Cham-
plain period; for much of it was owing to the piling of the
flooded waters in the narrow valley. The distance from Basle
in a straight line to the North Sea at the mouth of the Rhine
is about 400 miles; and if the flood from the melting glacier
increased the slope of the surface of the waters on an average
only 2 feet a mile, the flood level at Basle would have been
800 feet above the present level of the river.
3. Recent Period.
The Champlain period was brought to a close by a raising
of the land over the higher latitudes, bringing the continent
finally up to its present level. This elevation placed the old
sea-beaches of the Champlain period high above the sea, at
their present level, that is, over 500 feet near Montreal, over
200 feet on the coast of Maine, and so on, as above stated;
and this level is approximately a measure of the elevation.
River- valleys, after the rise, had a much steeper slope than in
222
CENOZOIC TIME.
the Champlain period, and hence their flow was increased in
rate. They consequently went on cutting down their beds
through the Champlain deposits of the valley to a lower level;
and at the time of their annual floods they wore away the
deposits on either side of the channel, making thereby an
alluvial flat or flood-ground, for every river has a flood-
ground which it covers in its times of flood, as well as a
channel for dry times. This sinking of the river-beds left
the old flood-grounds as a high terrace far above the level of
Fig. 237.
Terraces on the Connecticut River, south of Hanover, N. H.
the stream; and the great elevated plains still remain to at-
test to the vastness of the floods from the melting glacier.
In the course of the elevation a series of terraces was often
QUATERNARY AGE. RECENT PERIOD. 223
made along the valleys, as illustrated in the accompanying
view (Fig. 237). A section of a valley thus terraced is repre-
sented in Pig. 238. The formation terraced is, as is shown,
the Champlain; and in the Champlain period it filled in gen-
eral the valley across (from f to f), excepting a narrow
channel for the stream, the whole breadth having been the
Fig. 238.
Section of a valley with its terraces completed.
flood-ground of the Champlain River. But after the elevation
of the land that closed the Champlain period began, the river
commenced to cut down through the formation, making one
or more terraces in it, on either side of the stream. In Fig.
238, R is the position of the river-channel after the terra-
cing; and on either side of it there are terraces at the levels
ff't d d', b b', and also another on the right side at r.
These terrace-plains are usually the sites of villages. They add
greatly to the beauty of the scenery along all water-courses.
The terraces fail where the valley is narrow and rocky.
Between the Champlain and Recent periods, or in the open-
ing part of the latter, Europe passed through a second, but
less severe Glacial epoch. Marks of it have been pointed
out in glacial deposits in the Alps and other places, but espe-
224 CENOZOIC TIME.
cially through the occurrence in great quantities of remains
of the Reindeer, a high-latitude animal, in Southern France.
With the bones of the Reindeer there are also those of
other cold-climate species. This epoch is called the Rein-
deer era; and the part of the Eecent period following it
the Modern era.
4. Life of the Quaternary.
L General Observations, The plants and the lower tribes
of the Animal kingdom in the early part of the Quaternary
were essentially the same as now. The species of corals mak-
ing coral-reefs in the tropics were probably in existence and
at work before the close of the Tertiary age; and the same
is true of part of the Insects, Eishes, Reptiles, Birds, and
Mammals of the modern world, perhaps of a large part.
There must have been some exterminations as a conse-
quence of the cold of the Glacial period, and of the ice of
high latitude regions. Many plants were driven south by
the coming on of the cold, and thus escaped destruction; and
some of these now live on Mount Washington and other high
summits of temperate North America. Birds must have short-
ened their northward migrations and lengthened them south-
ward, and for the most part may have escaped catastrophe.
The beasts of prey, cattle, and other large mammals of Drift
latitudes must also to a great extent have moved toward the
tropics as the rigors of the approaching ice-period began to
LIFE OF THE QUATERNARY AGE. 225
be felt. Certain it is, that after the ice had gone there was
a large population of brute Mammals over Europe and the
other continents ; and facts seem to prove that they hung
about the southern limit of the ice, and often moved north-
ward with the lulls in the intensity of the climate or thej
shortening-in at intervals of the ice-field.
2. Brute Mammals. The brute mammals reached their maxi-
mum in numbers and size during the warm Champlain period,
and many species lived then which have since become extinct.
Those of Europe and Britain were largely warm-climate spe-
cies, such as now are confined to warm temperate and tropical
regions ; and only in a warm period like the Champlain could
they have there thrived and attained their gigantic size. The
great abundance of the remains and their condition show that
the climate and food were all the animals could have desired.
They were masters of their own wanderings and had their
choice of the best.
The relics have been found in deposits along the margins
of rivers and lakes; in marshes, where they were mired; in
caves, buried in the stalagmite (page 24) that had been
deposited over them. In Britain and Europe the caves were
the haunts of Bears, Hyenas, and Lions, much larger than
any of the kind now living ; these beasts of prey dragged
into them the bodies of the animals they fed upon. The
Cave-Bear resembled much the Grizzly Bear of Western
North America; and the Cave-Hyena and Cave-Lion are re-j
10* o
226 CENOZOIC TIME.
garded as the same in species with the African Hyena and
( Lion, although these modern kinds are dwarfs in comparison.
With these there were in Britain and Europe species of
Bhinoceros, a Hippopotamus, the Siberian Elephant or Mam-
moth, the Brown Bear, Wolf, Wildcat, Lynx, Leopard, Fox,
Elk, Deer, and others. The modern Horse was among them,
/yet gigantic in size like many of the other Mammals of that
V genial period. The Irish Deer (Cervus megaceros), skeletons of
which have been found in Irish bogs, had a height to the tip
/ of the antlers of 10 to 11 feet, and the span of the antlers
was sometimes 12 feet. The Elephant (lElephas primigenius)
and the most common Ehinoceros (B. tichorinus) had a hairy
covering, and this fitted them to wander off into regions far
north; their remains, especially those of the Elephant, show
that they lived in great herds over Northern Siberia, where
now the mean temperature of the year is 5 to 10 F. The
Ehinoceros had a length of 114 feet, and the Elephant was
nearly a third taller than the largest of modern Elephants.
In North America also there were large Lions and Bears,
but none of them, as far as known, made caves their dens.
The largest of the species was the Mastodon (Fig. 239), an
animal with tusks and trunk like an Elephant. When full
grown it was 12 to 13 feet in height, and to the extremities
of the tusks 25 feet long. The teeth had a crown as large in
area as this page, and of the form shown in Fig. 240. Skele-
tons have been found in marshes where the heavy beasts were
LITE OF THE QUATERNARY AGE.
227
mired; and portions of their undigested food the small
branches of spruces and other trees have been taken from
between their ribs, where the stomach once was.
Fig. 239.
Skeleton of Mastodon Americanos.
There were also American Elephants of great size, much
resembling the Siberian. Fig. 241 represents a tooth of one
of them found in Ohio ; it is a little larger than that of the
Mastodon. There were also Horses of large size, Tapirs, Oxen,
Beavers, and various gigantic species of the tribe of Sloths.
The Sloth tribe was especially characteristic of South
America. The modern Sloth is as large as a Dog of medium.
228
CENOZOIC TIME.
size. These species of the Champlain period included a Me-
gatherium (Fig. 242), which was larger than the largest of
Figs. 240, 241.
. Teeth of Mastodon and Elephant.
Fig. 240, Mastodon Americanus (X #) ; 241, Elephas Americanus (X #)
existing Ehinoceroses. As the figure shows, it was a lazy
beast, the bones of the hind legs being much like logs, and
Fig. 242.
Megatherium Cuvieri (X 'As).
those of the fore-feet furnished with hands a yard long for
LIFE OF THE QUATERNARY AGE. 229
pulling down trees after raising itself erect on its hind
legs and enormous tail a third support for the purpose.
This is one of many kinds of gigantic Sloth-like animals that
lived in South America during the era. Other related species
had a shell somewhat like the modern Armadillo; and these
also were gigantic, one of them (Fig. 243) measuring 5 feet
across its shell, and having a length of at least 9 feet.
Fig. 243.
Glyptodon clavipes (X */ }0 ).
In Australia the Mammals are now, with some small ex-
ceptions, Marsupials, the Kangaroo being one of them.
They were also Marsupials then; but the ancient kinds par-
took of the peculiar feature of the era, great magnitude,
some of the species being as large as a Hippopotamus, one
having a skull a yard long, and many of them being far
larger than any modern Marsupial.
Thus the brute races of the Middle Quaternary on all the
continents exceeded the moderns greatly in magnitude. Why,
no one has explained.
230 CENOZOIC TIME.
The genial climate of the Champlain period was abruptly
J. L terminated. Eor carcasses of the Siberian Elephants were
frozen so suddenly and so completely at the change, that the
flesh has remained untainted. Near the close of the last cen-
tury, one huge carcass dropped out of the ice-cliff at the
mouth of the Lena, and for a while made food for dogs.
The existence of a hairy covering was then first ascertained.
A hairy Rhinoceros has also been found in the ice. This
change of climate was probably connected with the commen-
cing of the Eeindecr or second Glacial era; and it was then
that the Reindeer and some other species succeeded in mi-
grating to Southern France, there to live until the cold epoch
had passed. The remains of the Reindeer are found along
with those of the Cave-Bear, Cave-Hyena, Rhinoceros, Ele-
phant, and other Champlain species, showing that all lived
together there at that time.
3. Man. Man was in existence during the Champlain
period; and probably in its earlier part before the ice had
disappeared (a part often included in the Glacial era by geol-
ogists) .
Relics, indicating that he was a contemporary of the gigantic
Champlain Mammals, occur in various caverns and in river
and lacustrine deposits, in Britain, Europe, Syria, and in
other regions.
The relics of Man are stone implements, such as arrow-
heads, hatchets, pestles, and stone chips made in the manufac-
MAN. 231
ture of the implements ; bones, shells, and other materials hav-
ing upon them his markings or carvings; his pottery; the
charcoal left from his fires; the bones of animals broken
lengthwise to get out the marrow; his own bones, skulls and
skeletons.
In Europe and Western Asia the stone implements of the
earlier part of what is sometimes called the Stone age are of
rude make and unpolished. This part of the age has been
called the Paleolithic era in human history, or that of the \
oldest stone implements, the word, from the Greek, signi-
fying old and stone. The stone implements occur along with
bones of the Cave-Bear, Cave-Hyena, Mammoth, Rhinoceros,
and several other Champlain species, and also with the bones
of Man; and these human relics are so associated with those
of extinct Mammals that there is no reason to doubt that
they were contemporaries.
Next came the Reindeer era. Its stone-implements are un-
polished, but better made than those of the preceding era.
Besides these there are examples of bones, shells, horn and
stone engraved with the forms of animals, and others that are
variously carved, or made into spear-heads and other forms,
and also perfect human skeletons. Fig. 244 represents a
drawing, on ivory, of the hairy Elephant; it was found in
the cave of La Madelaine, in Perigord, Southern France, and
shows that the Elephant was well known to the men of the
period. These human relics are associated with remains of
232
CENOZOIC TIME.
7
the same Champlain Mammals that occur in the earlier de-
posits,, and also with great numbers of the bones of the
Itaindeer, and many of the Aurochs, Elk, Deer, and other
species of later time.
Fig. 244.
Elephas primigenius ; engraved on ivory (X Y s ).
Next followed an era in which the implements were still
of stone, but often polished, and in which the remains of the
E^indeer are rarely found, and those of the peculiar Cham-
plain species not at all, but instead portions of skeletons of
the domestic dog and other existing quadrupeds, with much
broken pottery. This era in the Stone age is called the Neo-
lithic, from the Greek for new and stone. The shell-heaps
(Kitchenmiddens) of the Danish Isles in the Baltic are among
the Neolithic localities.
The bones and skeletons of Man of this Stone age in no
case indicate a race inferior to the lowest of existing races,
or intermediate between Man and the Man- Apes, the species
among the brutes which approach him most nearly. But still
MAN. 233
they are those of uncivilized Man, and in part of Man of a
low order of faculties.
The skeleton of Neanderthal (a part of the valley of the
Diissel, near Diisseldorf) is the worst, but it is not older
than others having better skulls and higher foreheads. The
capacity of the cranium was 75 cubic inches, which is greater
than in some existing men. A jaw-bone of low type, found
in the oldest Belgian deposits, had little height and great
thickness, as if for powerful use, and the posterior of the
molar teeth was the largest, a brutal feature.
The skeletons of the Reindeer era in Southern Prance are in
part those of men of unusual height, 5 feet 9 inches to
over 6 feet ; and the skulls are large and well shaped, with
the foreheads high and capacious. They are of better size and
shape than many of the Reindeer era in Belgium, which are
small and after the Laplander type.
One of the most perfect was found in the stalagmite that
formed the floor of the cave of Mentone, near the borders of
France and Italy, on the Mediterranean. Eight feet above it in
the stalagmite there were remains of the extinct Rhinoceros
and other Champlain species. The man would compare well,
if we may judge from the skeleton, with the best among
civilized races, his forehead broad and high, and rising with
a facial angle of 85, his height 6 feet; and yet he was a
European savage of the Reindeer, if not Paleolithic era; for
about him lay his flint implements and weapons, his chaplet
234 CENOZOIC TIME.
of stag's canines, and shells that he had gathered for food
or ornament from the shores near by. The tibia or shin-bone
was somewhat flattened, a peculiarity often observed in the
skeleton of the American Indian. The brain-cavity of a skull
found in the cave of Cro-Magnon, in Southern Prance, had a
capacity of 97 cubic inches, which is very much above that
of ordinary Man, and nearly three times that of the highest
Man-Ape.
In North America cases of the occurrence of ancient human
bones or skeletons in Quaternary deposits are not as well
authenticated as those in Europe. Admitting the facts that
have been published, they do not give Man greater antiquity
than those above mentioned.
No case of the presence of human relics in deposits of the
Tertiary age on any continent is yet well established. Mr.
W. Boyd Dawkins, an excellent British geologist and original
observer in this department of the science, states, in his recent
work on Cave-Hunting (1874), that the evidence obtained
proves that "Man lived in Germany and Britain after the
maximum Glacial cold had passed away," and that no human
remains te have been discovered up to the present time in
any part of Europe which can be referred to a higher an-
tiquity than the Pleistocene (Quaternary) age." The human
relics thus far found in Syria and Asia lead to no greater
antiquity for Man. Migration into Europe along with the
Champlain Mammals in pre-Glacial time is suspected; but on
this point there are as yet no known facts.
GEOLOGICAL WORK STILL GOING FORWARD. 235
The second Glacial epoch in Europe and Asia (which
there is reason to believe produced effects also in North
America) appears to have finally brought to a close the era
of giant beasts, leaving the world for Man.
The Age of Man still continues; and now it has as its j
fossils, not only flint implements and human bones, but also I
buried cities, temples, statues, manuscripts.
The system of life, long in progress, finally reached its
completion in a being that could search into the earth's his-
tory, study Nature's laws, investigate the system of the uni-
verse, judge of right and wrong in himself and others and
will the right; and who has thus the highest credentials of
kinship with the Infinite Author of physical and moral law.
The progress of chief interest hence is no longer the develop-
ment of animal races and characters, but the exaltation of
Man in the direction of his higher nature.
5. Geological "Work still going Forward.
Rock-making has not yet ceased; for the old agencies
the waters, the winds, and life are still at work with un-
impaired energies. Sand-beds, pebble-beds, and mud-beds are
accumulating along sea-shores and in shallow waters, precisely
like those that were hardened into ancient sandstones, con-
glomerates, and shales; and limestones are forming from shells
and corals similar to ancient limestones. Moreover, modern
236
CENOZOIC TIME.
Fig. 245.
Dodo, with the Solitaire in the background.
From a painting, at Vienna, made by Roland Savery, in 1628.
LENGTH OE GEOLOGICAL TIME. 237
fossils include, besides human remains, corals, shells, and
relics of all the various tribes of the era, as in past time.
Further, species are becoming extinct; at least through
Man, if not in other ways. The Dodo, an extinct chicken-
like bird of 50 pounds weight (Fig. 245), was living on
Mauritius in the 17th century. The Moa, larger than an
Ostrich, and other birds with it, have recently disappeared
from New Zealand. The Aurochs (Bison prisons] of Europe
is nearly extinct. Thus wild animals have begun to disap-
pear before advancing Man. The same is true of plants.
Again, changes of level are still going on. A large part
of Sweden is rising at the slow rate of 4 feet or so a cen-
tury, and as slowly a portion of Greenland is subsiding.
Such movements, along with earthquakes, prove that contrac-
tion from the cooling of the earth's crust has not ceased.
Hence, although the earth is in its finished state, enough
of geological work is now going on to enable Man to decipher
the records of the past.
V. Observations on Geological History.
I. Length of Geological Time.
To the question, "What is the length of geological time,
geology gives no definite reply. It establishes only the gen-
eral proposition that time is long.
238 GEOLOGICAL HISTORY.
The Canon of the Colorado (page 78) is a gorge 200
miles long, bounded the most of the way by steep walls
of rock over 3,000 feet in height, cut through sandstones,
limestones, and other rocks, and at bottom over parts of it,
for several hundred feet, into granite; and above the lofty
walls a few miles back from the stream the pile of nearly
horizontal strata is continued in mountains to a height of
(7,000 to 8,500 feet above the bed of the river. All the
facts, as its describers testify, point to running water as the
agent that made the great channel. The region was under
the sea until the close of the Cretaceous period, for marine
Cretaceous strata are the uppermost rocks. It follows, then,
that all this extensive excavation was accomplished by slow-
acting water during Cenozoic time. Surely Cenozoic time was
very long.
The gorge of the Niagara Eiver below the Falls has a
length of 7 miles. It is the work of the waters since the
middle of the Champlain period; for in the first place, a
former channel leading from the Whirlpool toward Lake On-
tario was entirely filled by the gravel and sands thrown in
by the melting glacier during the earlier part of that period;
. and, secondly, Champlain beds containing shells of Lake Erie
and a tooth of the Mastodon, formerly spread over the place
where the gorge now is, as shown by the remains of the for-
mation above on the Canada side. The water has conse-
quently made this vast excavation, 7 miles long, since Man
LENGTH OF GEOLOGICAL TIME. 239
appeared. The rate of progress of the Falls up stream is
not satisfactorily ascertained; the most rapid rate that has
been estimated would give more than 30,000 years for they
work.
The thickness of a sedimentary deposit is no satisfactory
basis for determining the length of time it took to form. In
a sea 100 feet deep 100 feet of sediment may accumulate;
and the thickness could not exceed this (except a little through
wave-action and the winds) if a million of years were given
to it.
Let the same region be undergoing a subsidence of an inch
a century, and the thickness might increase at that rate; and
much faster if a yard a century; and with either rate, giving
time enough, any thickness might be attained. Hence a stra-
tum of sandstone 100 feet thick may have been formed in a
thousandth part of the time of a thin intervening bed of shale.
Nevertheless, the aggregate maximum thickness which the
strata attained during the several ages may be used for an
approximate estimate of the comparative lengths of those
ages. On such data, it is ^deduced that the time-ratio for
Paleozoic, Mesozoic, and Cenozoic time was not far from
12 : 3 : 1. Consequently, if we suppose the length of time
since the Paleozoic began to be 16 millions of years, Paleo-
zoic time will include 12 millions, Mesozoic 3 millions, and
Cenozoic 1 million. Most geologists would make the whole
interval several times 16 millions.
240 GEOLOGICAL HISTORY.
2. Progress in Features.
The earth through the ages made progress,
1. In its surface features: from the condition of a melted
sphere as featureless as a germ,, to that of an almost univer-
sal ocean with small lands, enough of land to mark out
the feature-lines of the future continents; and at last after
slow expansion southward, a lifting of mountain ranges at
long intervals, and a retreating of the waters to the exist-
ence of great continents having high mountain borders and
well- watered interior plains.
2. In its river-systems: from the existence of only little
streamlets draining small lands in the Archaean and Silurian
eras, and making no permanent geological record beyond a
rain-drop impression; to a condition of vast fresh-water lakes
and marshes when beds of vegetable material accumulated for
the making of coal-beds; and finally to that of the completed
continent, when a single river with its tributaries drains,
waters, and contributes fertility to hundreds of thousands of
square miles of surface, and the work of fresh waters in rock-
making exceeds that of the ocean.
3. In its climate: from a condition of general uniformity
of temperature, to, at last, though with interrupted progress,
that of the present diversity, when the poles have a per-
manent capping of ice, and only the equatorial regions per-
petual verdure.
PROGRESS IN FEATURES. 241
4. And, again, in its living adornments: from an era when
the ^small rocky lands were bare, or gray and drear with
lichens, and all other life was of the simplest kind and below
the water-level; to a time of flowerless forests and jungles
over immense plains, yet with no sounds from living Nature
more musical than the Amphibian's croak; and onward to
the better time when the earth abounds in flowers and fruits
and birds, and is covered with the homes of Man.
3. The System of Nature of the Earth had a beginning
and will have an end.
A system of progress or development in the earth as much
implies that it had a beginning, as that in any plant or ani-
mal. Man, Mammals, Fishes, Mollusks, Rhizopods, Plants,
all had, according to geological history, their beginning; so
also mountains, valleys, rivers, continents, rocks. And so
also the earth; and therefore the system of nature, whose
development went forward in and through it, had its begin-
ning.
If this is true of one sphere in space, we may rightly take
another step and assert that the universe had its beginning.
It also admits of demonstration that the earth will have its
end. A finished state is always the state before decline and
death. The earth is dependent for all the beauty in its liv-
ing adornments, and even for the existence of its life, on the
heat and light of the sun. The sun is losing annually its
11 *
GEOLOGICAL HISTORY.
heat; and however infinitesimal the amount of loss, it is sure
to end in a cooled and dark sun; and hence, even long be-
fore the sun is cold, the earth, supposing it to have met with
no earlier catastrophe, will have become dark and lifeless,
literally a dead earth.
4. Progress in Life.
1. The progress in life was in general from the simpler
forms to the more complex, or from the low to the high.
This truth has been illustrated in each chapter of the pre-
ceding geological history.
2. The progress was by gradual steps. Species appeared
and disappeared, not only at the beginning of ages, or of the
subdivisions of ages called periods, but also during the pro-
gress of periods, each of the successive strata containing some
fossils not found below, and failing of others that are abun-
dant in underlying beds. There were at times epochs of wide-
spread catastrophe, ending periods, and two of them, those
closing Paleozoic and Cenozoic time, were nearly or quite
universal for the continental seas. But these must have left
unharmed the life of the deep ocean; and they may not have
exterminated all the life of the emerged land, or even of the
whole area of continental seas.
3. The progress was according to system. The first animal
life was probably the Protozoan, or Ehizopods, Sponges, and
the like; kinds that are minute and destitute of members.
PROGRESS IN LIKE. 248
But later the four great systems of structure the Radiate,
Mollusk, Articulate, and Vertebrate were denned; and the
species which appeared afterward in the long succession were
constructed according to one or the other of these systems.
Each system, by the new species that came into existence as
time moved on, became displayed in higher and more diver-
sified forms. The first of the Vertebrates were the Fishes,
the simplest of its tribes. Even in these limbless species
the arms and legs of the higher Vertebrates were present,
though only in the state of fins; and the lung, though only
as a cellular air-bladder ; and the ear, though only as a closed
cavity containing a loose bone; and so with other parts.
Thus the earliest of Vertebrates possessed in an incipient stage
many of the organs that became fully developed in the later
and higher Vertebrates. And in the succession of species that
existed, all were made on the fish-structure as its basis, even
the species of the highest class, those of Mammals and
Man. A zoologist, in order to understand the fundamental
elements in the human structure, goes to the fish and the
frog for instruction; and Nature is so true to her funda-
mental principles, that he there finds what he looks for.
4. The system of progress is rightly called a system of de-
velopment or evolution. With every step there was an un-
folding of a plan, and not merely an adaptation to external
conditions. There was a working forward according to pre-
established methods and lines up to the final species, Man,
244 GEOLOGICAL HISTORY.
and according to an order so perfect and so harmonious in
its parts, that the progress is rightly pronounced a develop-
ment or evolution. Creation hy a divine method, that is, by
the creative acts of a Being of infinite wisdom, whether through
one fiat or many, could be no other than perfect in system,
and exact in its relations to all external conditions, no other,
indeed, than the very system of evolution that geological history
makes known.
5. The system not one of regular progress upward, but one
involving the culmination and decline of some tribes as the
general unfolding went forward. As has been brought out
in the history, the division of Trilobites, Brachiopods, and
Crinoids, besides others, reached their maximum, or culminated,
in Paleozoic time; of Amphibians, in the first period of the
Mesozoic era; of Eeptiles and Ganoids among Vertebrates,
and of Cephalopods, the highest of Mollusks, in the later
Mesozoic; of brute Mammals, in the Champlain period of
Cenozoic time. So, again, in the kingdom of plants, the
highest Cryptogams the Acrogens culminated in the Car-
boniferous period, that is, the later Paleozoic; Cycads, in the
middle Mesozoic ; while Palms and Angiosperms have the present
era as their time of greatest display and perfection. These
are a few examples, showing that progress did not go on
regularly upward; but that the old, not only in species, but
also in tribes and orders, were culminating and then passing
away, as new and higher tribes were introduced, in the pro-
gressing evolution of the kingdoms of life.
PROGRESS IN LIJFE. 245
6. Parallelism between the progress of the system of life and
the progress of individual life. An animal, in its growth from
the germ, or, as it is called, its embryonic development,
passes through a succession of forms before reaching the adult
state. In Mammals the changes after birth are small, the larger
part of them having taken place before birth. But in the lower
animals the successive forms are often widely diverse, and they
frequently mark successive stages in the life of the animal.
Thus, in Insects, there is the caterpillar or grub stage, before
the adult; and in many Crustaceans, Mollusks, Worms, and
Radiates there are several such stages.
Now species have existed and many now exist which
have the general characters of the forms in these lower stages ;
and, in accordance with the above proposition, the order of their
appearance in the geological series is, in general, as announced
by Agassiz, that of their development in the embryonic series.
Thus, as the worm-like grub precedes the adult insect, so
Worms, in geological history, preceded Insects. As a fish-like
condition of an Amphibian precedes the adult form in which
the fish-like feature is lost, so Fishes preceded Amphibians.
The examples of the principle are numerous. Some authors
have so great faith in it, that they are ready to decide as to the
form of the earliest species of a tribe from the earlier stages
in individual development. But this is unsafe, since such forms
may have come late into the system of life as well as early;
inasmuch as progress was not' in all cases upward progress.
246 GEOLOGICAL HISTORY.
Where the parallelism above mentioned is not apparent in
the general form or structure, it is still manifested in certain
comprehensive laws common to both kinds of progress, the
geological and embryonic. The following are some of these
laws.
a. The low before the relatively high.
6. The simple before the complex. A germ has little dis-
tinction of parts ; the animal it is to evolve is there in a very
general condition, that is, without any special organs. As de-
velopment of a Mammal goes on, the denning of the head be-
gins, and this is one of the first steps in the evolving of special
parts, or in the specialization of the structure. Protuberances
also form and commence the defining of the limbs ; and then,
finally, the parts of the limb become distinct, or are specialized.
Thus it is throughout the structure, until the specialization of
the parts peculiar to the particular animal is completed.
This law of the general before the special is a law also in
the geological progress of the system of life. In a fish, the
earliest of Vertebrates, the vertebrate structure is exhibited in
its most generalized condition. The vertebral column consists
of one single uniform range of vertebrae without a neck portion,
and without a pelvis to divide the body from a tail and afford
support to hind limbs ; the limbs are fins, and hence only rudi-
ments of limbs ; the vertebrae have great simplicity of form ;
the teeth are all of the simplest kind ; the lung is merely an
air-bladder, and so on. Thus, all through the structure, a fish
PROGRESS IN LIFE. 247
is an exhibition of the vertebrate type in a generalized state.
The Vertebrates which succeeded to fishes, the Amphibians,
have the grand divisions of the body well brought out, and are
specialized also as to limbs even to the toes, and in other ways.
Passing onward in time, the new Vertebrates appearing exhib-
ited successively a more and more complete specialization of
organs and functions, up to Man. In the development of Man
from the embryo, it is not true that he passes through a fish-
like condition ; but it is the case that certain fish-like charac-
teristics may be observed in the structure, during its earlier
progress ; and one of these is an opening beneath the jaws, (
which Dr. Wyman has regarded as representative of the gill- j
openings of Fishes.
This law of progress by specialization has its exceptions ; for
Snakes, which are limbless, succeeded to higher reptiles which
had limbs. But such cases only exemplify another fact, al-
ready illustrated, that, while upward progress was the rule,
there was also progress downward, and especially after the time S v
of culmination of a tribe had passed.
c. Stationary forms sometimes before the locomotive. Thus,
(1.) Crinoids, part of the earliest life of the globe, were sta-
tionary species living attached by a stem; and, after these,
there were free Asterioids. So the young of the modern Cri-
noid has a stem for attachment, and loses it, in many spe-
cies, as it becomes an adult (a Comatulid). (2.) The earliest
Brachiopods were attached species, and so are the young of
all existing Brachiopods.
248 GEOLOGICAL HISTORY.
d. Forms in a group having the body elongated posteriorly,
and endowed behind with locomotive power, generally precede
those that are shorter behind and superior in the anterior por-
tion of the body and head, a headward transfer of the forces
of the structure marking all upward progress. The young of a
crab has an elongated locomotive tail-extremity, which it loses
as it develops to a crab ; and so the long-tailed shrimps pre-
ceded crabs in geological history. The young of a modern
Ganoid or gar-pike has an elongated verteb rated tail, which it
loses with the change to the adult; and so Ganoids in Palae-
ozoic time had vertebrated tails, but in Mesozoic time lost them.
In the young of some birds the tail segments of the vertebral
column are much elongated and free, but, with progressing
development, they become greatly contracted, and often con-
solidated together; and so the earliest Birds, in part, at least,
had long vertebrated tails. The young of an Insect is an elon-
gated, worm-like grub ; and so Worms preceded Insects. The
embryo of Man in an early stage of development has a tail half
as long as that of a dog in the same stage.
The principle is a general one through the animal king-
dom. This shortening behind is directly connected with, or
a consequence of, a transfer forward of the forces of the ani-
mal structure by which improvement is given to the anterior
extremity, and a higher grade of power and functions to the
head. Progress from the embryo in animals is always attend-
ed with a gradual improvement of the head extremity, and
PROGRESS IN LIEE. 249
also with changes of form in adaptation to it ; and, parallel
with this, progress in the system of animal life, from its
earliest beginnings onward, was similarly attended, under all
tribes, by a headward transfer of power in the being, and by
such structural changes as this involved. Marsh has shown
that the Carnivores and Herbivores of the early Tertiary had (
brains but a half or a third as large in bulk as those near- (
est related to them in type and size among modern species.
This kind of progress is progress in capitalization ; this
term being derived from the Greek for head. And the prin-
ciple here illustrated may be briefly announced as follows :
Progress both in the system of animal life and in individual
life is eminently progress in cepJialization.
Man, the last and highest being in the system of life, de-
rives his exalted position from the extreme degree of cephaliza-
tion which characterizes his structure. Besides having a great
brain and great head power, his fore-limbs are removed from
the locomotive series, and turned over to the service of the
head, and, as is involved in this transfer, his body is erect.
Thus, by an abrupt transition, he stands apart from the ape
and all brute races.
7. The transitions between species, in the system of progress,
not yet proved to be gradual The systematic succession in
the progress of life, made manifest by facts derived from the
rocks, leads many to hold that the whole has been as much a
growth under the control of physical law as is proved to be
250 GEOLOGICAL HISTORY.
true of the development of the earth's features. Geological
history has accordingly been appealed to for evidence as to
whether species, instead of being independent types of structure,
are so linked together by gradual transitions, that we cannot
reasonably avoid the conclusion of their production from one
another by gradual change. That evidence it has not yet af-
forded. This is admitted by all, even by those who believe
that the transitions were gradual. Geology has brought to
light fewer examples of gradual transition than occur among
living species. The wide intervals that have separated related
groups are diminished from time to time by the discovery of
remains of intermediate species. It has been thus for the
interval between the Elephant and Mastodon, and for that be-
tween the Horse of modern time and the Tapir-like animals
of the early Tertiary (page 204) ; and the same in many other
cases. And yet the new species found have still strong specific
differences, arid those that have thus far been discovered between
the Horse and Tapir are of distinct genera ; so that the idea
of abruptness between species is not yet set aside by geological
evidence.
But geological evidence on this point is, as has been often
urged, far from satisfactory. The record is unquestionably
very imperfect. The following are examples.
It is certain that there were birds in the Jurassic period
in Europe, for one with its feathers has been found fossil.
But thus far we know of but that one specimen out of the
many; for if there was one there were myriads.
PROGRESS IN LIFE. 251
There is the same evidence that there were Marsupial Mam-
mals during the Triassic era in North America, and therefore
during the Jurassic and Cretaceous eras following; and yet
only two jaw-bones of Triassic Marsupials have been found in
all the American Mesozoic rocks.
There was abundant life in the oceans of the long Triassic
and Jurassic eras; but, nevertheless, not a fragment of any
species has been found in the Triassic or Jurassic rocks on
the Atlantic border of North America; and the Triassic of
the Rocky Mountain region is as destitute of marine life. The
American record respecting marine species of the Atlantic
border for the long time between the Carboniferous and Cre-
taceous eras is utterly a blank.
Again, of the plants of the great forests that covered the
American continent in the Triassic and Jurassic eras less than
50 species are known; and yet the whole of the dry land of
the continent must have been covered, and the kinds through
all that time must have been very numerous.
These are examples of the imperfection in the record, and
they naturally weaken much the force of geological evidence.
But if they weaken it, they do not authorize the conclusion
that the transitions were always gradual.
There are some gaps of great width. Of the species con-
necting Mollusks or other Invertebrates with the first of
Eishes, geology has afforded not a fact: it has found only
great Sharks, Ganoids, and Placoderms as the earliest spe-
252 GEOLOGICAL HISTORY.
cies. With regard to the Palms, which first appeared in the
Cretaceous, none of the preceding links have been found; and
none for the Elm, Magnolia, and various other Angiosperms
that accompanied the first Palms. Bones of true Mammals
are very abundant in the Tertiary strata; and yet in the Cre-
taceous beds, those next earlier, there are numerous remains
of great Reptiles, and not a trace, as yet observed, of the
true Mammals.
8. Origin of Man. The interval between the Monkey and
Man is one of the greatest. The capacity of the brain in the
lowest of men is 68 cubic inches, while that in the highest
Man- Ape is but 34. Man is erect in posture, and has this
erectness marked in the form and position of all his bones,
while the Man- Ape has his inclined posture forced on him
by every bone of his skeleton. The highest of Man-Apes, the
Orang-utan, cannot walk without holding on by his fore-
limbs ; and, instead of having a double curvature in his back
like Man, which well-balanced erectness requires, he has but
one. The connecting links between Man and any Man- Ape
of past geological time have not been found, although earnestly
looked for. No specimen of the Stone age that has yet been
discovered is inferior, as already remarked, to the lowest of
existing men; and none is intermediate in essential characters
between Man and the Man-Ape. Until the long interval is
bridged over by the discovery of intermediate species, it is
certainly unsafe to declare that such a line of intermediate
species ever existed, and as uuphilosophical as it is unsafe.
PROGRESS IN LIFE. 253
If, then, the present teaching of geology as to the origin
of species is for the most part indecisive, it still strongly
confirms the belief that Man is not of Nature's making.
Independently of such evidence, Man's high reason, his un-
satisfied aspirations, his free will, all afford the fullest assur-
ance that he owes his existence to the special act of the
Infinite Being whose image he bears.
9. Man the highest species. It is sometimes queried whether
the future may not have its various new species of life, and,
among them, some higher than existing Man; whether the
age now passing is not to be followed, as was true of the
Carboniferous, or the Reptilian, by another still more glorious
in its living species; whether, if one of the great Dinosaurs
of the Mesozoic age could have thought about his own and
other times, he would not have imagined his age the last and
the best possible, and whether Man is not playing as foolish
a part in styling himself the " lord of creation."
Against the introduction of new species in coming time
science has little to urge. But there is strong reason for
holding that, whatever the changes in the lower tribes, exist-
ing Man will always remain the highest in the series.
(1.) Science has made known that the highest of species
next to Man, that is, the brute Mammals, have already passed
their maximum (page 225) ; hence, the rest of time remains
for the culmination of the only higher type, that of Man.
And, as this type includes now but one species, we have rea-
son for expecting no new species in the future.
254 GEOLOGICAL HISTORY.
(2.) From geological history we learn also that the type of
Yertebrates commenced in kinds that were horizontal in atti-
tude, the Fishes; and that from the horizontal there was,
in the B/eptiles and Mammals, a raising of the head above
the line of the body, up to the Ape, in which the attitude is
nearly vertical; and, finally, to perfect vertically in Man, a
being having the head placed directly over the body and hind
limbs. Thus, as Agassiz observed, the last term in the series
has been reached; there can be nothing beyond. This is true
as to the general type of structure; but it leaves it an open
question whether there may not be other species of Man, or
erect beings, of still higher grade.
(3.) But a different species of Man higher than existing Man
is not a possibility. We can conceive of other species of Man
distinguished by having some of the external features of the
Man-Apes. But these are marks of inferiority, and, if possi-
ble in a type of so high grade, could belong only to inferior
species.
The increasing erectness and breadth of forehead in Man,
and the shortening of the jaws, giving a nearly vertical line
to the front, which are a known result of culture, indicate
the course which upward progress must take. And in these
points and some others closely related, the limits of perfec-
tion have been nearly reached by some among the present
race. Further improvement can give physically only larger
capacity to the brain and greater beauty of form to the
PROGRESS IN LIFE. 255
whole structure, and make these qualities more general. No
wide divergence from existing Man can be conceived of.
When all possible change in these directions has been accom-
plished, Man will still be Man, and no more the head of the
system of life than he is at present.
(4.) Beyond all this we may say, that since no Dinosaur, and
no other species but Man, has ever been capable of reviewing
the past or contemplating the future; and since Man not only
has all time and all Nature within the range of his thought
and study, but can even yoke Nature for service, and in fact
has her already at work for him in numberless ways, the
system with such a head must be complete.
Nature, through Man, has attained to the possession of a
living soul capable of putting her once wasted energies into
strong and combined movement for social, intellectual, and
moral purposes, and this is the consummation that the past
has ever had in prospect.
The Man of the future is Man triumphant over dying
Nature, exulting in the freedom and privileges of spiritual
life.
INDEX
NOTE. The pronunciation of some of the scientific words is indicated by an accent.
ACONCA'GUA, 65.
Ac'rogens, 103.
Carboniferous, 156.
Adirondacks, 107-
Agate, 5.
Ages in Geology, 99.
Alabama Eocene, 201.
Albite, 2.
Algae. See SEA-WEEDS.
Alleghany Mountains, making of, 168.
Alluvial deposits, 49.
Alps, glaciers in, 58.
elevation of, 20?.
Amethyst, 11.
Ammonites, 182.
Amphibians, 163, 186.
Amygdaloid, 18.
An'giosperms, Cretaceous, 181.
Tertiary, 200.
Anisopus, tracks of, 18?.
Anthracite, 154.
origin of, 171.
Anticli'nal, 85.
Apennines, 207-
Appalachians, making of, 168.
Appalachian region, 135, 136, 167.
folded rocks of, 85, 169.
thickness of formations of, 167.
Archse'an time, 106.
North America, 108.
Arequi'pa, 65.
Argillaceous sandstone, 15.
Ar'gyllite, 15.
Articulates, 100.
As'aphus gigas, 126.
As'terophyllites, 140.
Astrsea, 28.
Atmosphere, agency of, 44.
Augite, 8.
Au'rochs, 232.
Aymestry limestone, 131.
Azoic. See ARCHAEAN.
BAI^ beds, 117-
Basalt, 18.
Basaltic columns, 22.
Beach-formations, 51.
Bear, cave, 225.
Belem'nites, 184.
Bilin, infusorial bed of, 36.
Birds, 101, 164.
Jurassic and Cretaceous, 190.
Tertiary, 203.
Bituminous coal, 154.
Black lead, 9.
Blue Ridge, 107.
Bog Iron-ore, 12.
Bowlders, 211, 214.
Bowlder-clay, 218.
Brachiopods, Silurian, 121, 133.
Devonian, 142.
Carboniferous, 152.
Brains, growth in, 247.
Brines of Salina, 130.
Bryozo'ans, 125.
CALAMI'TES, 140, 158.
Calcareous rocks, 14, 27.
Calcite, 9.
Calyme'ne Blumenbachii, 126.
Cambrian. See PRIMORDIAL.
Camel, Tertiary, 206.
Cannel coal, 154.
Canon. See COLORADO.
Carbon, 8.
Carbonate of lime, 9.
Carbonic acid, 9.
Carboniferous age, 149.
258
INDEX.
Carboniferous age, changes during, 164.
Car'ni-vores, 304.
Carpathians, 207.
Catskill period, 138.
Cave animals of Quaternary, 225.
Cenozoic time, 194.
Centipedes, 162.
Cephalization, progress in, 249.
Cephalopods, 123.
of Mcsozoic, 182.
Cestracionts, 145.
Chain-coral, 132.
Chalcopy'rite, 13.
Chalk, 179.
Chainplain period, 218.
Chemung beds, 138.
Cincinnati uplift, 135, 165.
Circumdenudation, 81.
Clay-slate, 15.
Climate, progress in, 238.
Mesozoic, 209.
Quaternary, 215, 218, 230.
Tertiary, 209.
Coal, kinds of, 154.
formation of, 155.
of Rocky Mountain region, 197-
sulphur in, 155.
Coal-areas, American, 152.
-areas of Britain, 153.
-beds, characters of, 153.
-beds, formation of, 165.
-beds of Triassic, 175.
-beds, flexures in, 169.
-measures, 151.
-period, 151.
-plants, age of, 103, 149.
Coccoliths, 34, 40.
Coccos'teus, 147.
Cockroaches, 161.
Colora'do, canon of, 20, 77, 78, 237.
Columna'ria, 119.
Conformable strata, 88.
Conglomerate, 14.
Conifers, Devonian, 142.
Carboniferous, 156, 160.
Mesozoic, 180.
Connecticut River sandstone and footprints, 175.
terraces, 222.
trap rocks, 194.
Continents denned in Archaean time, 108.
origin of, 94.
Contraction a cause of change of level, 89.
Copper ore, 13.
00^13,27-30.
Silurian, 109, 119, 132.
Devonian, 142.
Carboniferous, 151.
Corallines, 34.
Corniferous limestone, 137.
Cotopaxi, 65.
Craters, 65.
Crepid'ula costata, 201.
Cretaceous period, 175.
America, map of, 177.
Great Britain, map of, 178.
Crinoidal limestone, 34, 150.
Cri'noids, 30, 34, 100.
Silurian, 119, 132.
Subcarboniferous, 150.
Crocodiles, 189.
Crusta'ceans, 100.
Cryp'togams, 103.
Crystalline rocks, 15-18, 26.
Culmination of types, 102.
Currents, oceanic, 50.
Cy'athophyl'loid corals, 142.
Cycads, 174, 181.
DAWKINS, W. B., on human relics, 234.
Decay of rocks, 42.
Deer, Irish, 226.
Delta of Mississippi, 49.
Den'udation, 48, 81, 86.
Detri'tus, 25.
Development, system of, 243.
Devonian age, 137-
hornstone, 138.
Diamond, 8.
Di'atoms, 5, 35.
Dikes, 65.
Dinoceras, 204.
Dinosaurs, 187.
Dip, 83.
Dodo, extinction of, 237.
Dol'eryte. See TEAP.
Dol'omite, 10.
Drift, 211, 213
sands, 45.
scratches, 212.
Dromatherium, 191.
Dunes, 45.
EARTH, first condition of, 106, 238.
progress in features, 238.
INDEX.
259
Earth, progress in life, 240.
Earthquakes, 64, 88.
Elephant, Quaternary, 226, 232.
Elevations, causes of, 80.
Emery, 6.
Ena'liosaurs, or Sea-saurians, 164, 188.
England, geological map of, 114, 178.
E'ocene, 194.
Eosau rus, 104.
Eozoon, 112.
Equise'ta, 139, 156.
Erosion, 48, 81.
Evolution, 243.
Expansion of rocks, effects of, 63.
FAULTS, 75, 87, 176.
Fa'vosi'tes, 143.
Feldspar, 6.
Ferns, Devonian, 139.
Carboniferous, 157, 158.
Fingal's cave, 208.
Fishes, 101.
Age of, 137-
Carboniferous, 161.
Devonian, 144.
Mesozoic, 185.
Silurian, 133.
Teliost, 186.
Fish-spines, 144.
Flags, 15, 139.
Flexures, 84, 89.
Flint, 4, 38, 180.
Flint arrow-heads, 230.
Folded rocks, 84, 89, 169.
Footprints. See TKACKS.
Foramin'ifers, 32.
Fossils, use of, in determining the equivalency
of strata, 97-
number of Paleozoic, 136.
Fox, Quaternary, 226.
Fractures, 87, 176.
Fragmental rocks, 15.
Fresh waters, action of, 46.
Fruits, fossil, 160.
GALE'NA, 13.
Gan'oids, Carboniferous, 161.
Devonian, 144, 145.
Triassic, 186.
Garnet, 8.
Gas'teropods, 122.
Geysers, 69, 73.
Giants' Causeway, 18, 208.
Glacial period, 211.
Glacier period of Switzerland, 58, 217.
second, of Europe, 223, 235.
scratches, 60, 221.
Glaciers, 58, 213.
Glyptodon, 229.
Gneiss, 16.
Gon'iatites, 183.
Gran'ite, 15.
Graph'ite. 9, 112.
Gravel, 15.
Greenland, changes of level in, 237-
Green Mountains, making of, 128, 135, 165.
limestone of, 128.
Green River Basin, 197.
Grit, 23.
Ground Pines, 131.
Gym'nosperms, 142.
Gypsiferous formation, Triassic, 176.
HALYSI'TES, 132.
Hamilton group, 138.
Hawaii, volcanoes of, 66, 68.
Heat, 63.
Height of Mount Shasta and other volcanic
peaks, 65.
Helderbcrg group, 130, 138.
Hem'atite, 11, 12.
Her'bi-vores, 203.
Highlands, 107.
Hippopotamus, 226.
Holoptych'ius, 146.
Hornblende, 7.
Hornblende rocks, 17, 109.
Hornstone, 4, 38.
Horse, fossil, 204, 226.
Hot springs, 68.
Human skeletons, fossil, 231.
Hyaena, cave, 225.
ICE of lakes and rivers, 57.
glacier, 58, 211.
Icebergs, 62.
down the Mississippi valley, 219.
Ichthyosaurus, 188.
Igneous rocks, 63.
Tertiary, 208.
Triassic, 194.
Iguan'odon, 188.
Infusorial earth, 36.
Insects, Devonian, 143.
260
INDEX.
Insects, Carboniferous, 162.
Invertebrates, 102.
Irish Deer, 226.
Iron ores, 11, 12.
Archaean, 109, 110.
Iron mountains of Missouri, 109.
JOINTS in rocks, 88.
Jorullo, 66.
Jurassic period, 175.
KILAUE'A, 67-
Kitchen-middens, 232.
LABKADOKITE, 7-
Lake Champlain in the Quaternary, 219.
Lakes of Rocky Mountain region, Tertiary, 196.
Lamellibranchs, 122.
Laminated structure, 15.
Lateral pressure, 89.
Lava, 19. .
Layer, 21.
Lead ore, 13.
Lemur, 264.
Lepidoden'drids, 141, 157.
Lepte'na, 121.
Level, change of, in Sweden and Greenland, 237-
changes of, in the Quaternary, 215, 218.
origin of changes of, 89.
Lias, 177.
Life, agency of, in rock-making, 27-
general laws of progress of, 240.
Lignite, 197.
Lignitic beds, 197, 202.
Limestone, 9, 10, 13
formation of, 27, 33.
Lingulella, 120.
Lingula flags, 117, 120.
Lion, cave, 225.
Lirioden'dron, 181.
Lithostrotion Canadense, 151.
Llandeilo flags, 117.
Llandovery beds, 117.
Lower He'lderbevg, 130.
Ludlow group, 131.
Ly'copods, 131, 141, 156.
Lynx, Quaternary, 226.
MADREPORA, 28.
Magnesian limestone, 11, 13, 116.
Magnetite, 11.
Mammals, 101.
Age of, 99, 194. .
Mammals, first of, 190.
Tertiary, 203.
Quaternary, 225.
Man, Age of, 209.
relics of, 230.
the head of the system of life, 237, 253.
origin of, 252.
Map of England, 114, 178.
of North America, Archaean, 105.
of North America, Cretaceous, 177.
of North America, Tertiary, 195.
Marble, 14.
of Green Mountains, 128.
Marsh, 0. C., growth of brains, 247.
Marsupials, 191, 203.
Quaternary, 229.
Mastodon, Quaternary, 226.
May-flies, Devonian, 144.
Medina group, 130.
Megaceros. See IRISH DEER.
Meg'alosaur, 188.
Megatherium, 228.
Mento'ne skeleton, 233.
Mes'ozoic time, 174.
Metamorphic rocks, 26.
Metamorphism, 71, 89.
Mia'mia Bronsoni, 144.
Mica, 7.
schist, 16.
Microscopic organisms, 32, 35.
Millstone-grit, 152.
Mineral coal. See COAL.
Miocene, 194.
Mississippi River, delta of, 49.
detritus of, 48.
valley, in the Glacial and Champlain pe-
riods, 219.
Missouri iron ores, 109.
Mollusks, 27, 100.
Monkeys, 204.
Monument Park, 82.
Moraine, 60.
Mo'sasaur, 190.
Mosses, 131.
Mountains, making of, 80, 83, 89, 171.
of Paleozoic origin, 128, 148, 167-
made during the Mesozoic, 193.
made during the Tertiary, 206.
Mount Holyoke, 194.
Hood, 208.
Loa,66.
Mansfield, glacial scratches on, 213,
INDEX.
261
Mount Shasta, 64, 208.
Tom, 194.
Mountains, White, scratches on, 213.
White, alpine plants on, 224.
Mud, 15.
Mud-cracks, 55.
Myr'iapods, or Centipedes, 162.
NAUTILUS, in the Silurian, 124
Neanderthal skull, 233.
Ne'olith'ic era, 232.
Niag'ara group, 129.
River, gorge of, 238.
Nova Scotia coal-measures, 166.
Num'mulites, 32, 33, 198.
Nummulitic limestone, 198, 199.
Nullipores, 34.
Nuts, fossil, 160.
OCEAN, effects of, 50.
life in depths of, 40.
Oceanic basin, origin of, 94.
Old red sandstone, 139.
On'onda'ga limestone. See UPPER HELDER-
BERG.
Oolyte, 178, 179.
Opal, 5, 73.
Ore'odon, 204.
Organic remains, rocks made of, 25.
Oris'kany sandstone, 131.
Orthis, 121.
Orthoceras, 124.
Or'thoclase, 7-
Ostrea sellseformis, 201.
Otozoum Moodii, 187.
Owl, 203.
Ox, first of, 206.
Oyster, Tertiary, 201.
PAL'^EASTER, 120.
Paleolith'ic era, 231.
Paleozo'ic time, 113.
Palisades, 194.
Palms, Cretaceous, 181.
Tertiary, 209.
Paradox'ides, 126.
Parrot, 203.
Peat, formation of, 40.
Pentac'rinus, 31.
Pen'tremi'tes, 151.
Permian group, 156.
Plac/oderms, 147.
Plants, Archaean, 112.
Carboniferous, 156.
Cretaceous, 181.
Devonian, 139.
lime-secreting, 34.
Lower Silurian, 117.
Upper Silurian, 131.
Tertiary, 200.
Triassic, 180.
Platephem'era antiqua, 144.
Ple'siosaurs, 189.
Pleurotoma'ria lenticula'ris, 123
Pliocene, 194.
Plumba'go. See GRAPHITE.
Polycystines, 37-
Polyps, 28, 100.
Polythala'mia. See FORAMINIFERS.
Porphyry, 19.
Portage group, 138.
Portland (England) dirt-bed, 1?9.
Post-tertiary. See QUATERNARY.
Potsdam sandstone, 116.
Primordial period, 116.
Productus, 152.
Progress of life, 242.
Pro'tozo'ans, 99, 112, 118.
Pterichthys, 147-
Pterodactyl, 191.
Pterosaurs, 190.
Pudding-stone, 14.
Pyrenees, 207.
Pyrite, 10.
Pyroxene, 8.
QUADRUPEDS. See MAMMAJLS.
Quaternary Age, 209, 224.
Quartz, 3.
Quicklime, 9.
RA'DIATES, 30, 99.
Rain-prints, 56.
Ran'iceps Lyellii, 163.
Recent period, 221.
Reefs, coral, 33.
Reindeer era, 224, 231.
Reptiles, 101.
Carboniferous, 161, 163, 164.
Mesozoic, 186.
Reptilian age, 174.
Rhine, alluvial deposits of, 221.
Rhinoceroses, Tertiary, 203.
Quaternary, 226.
262
INDEX.
Rhi'zopods, 32, 33, 40, 99.
Archaean, 112.
Cretaceous, 179.
Ripple-marks, 54.
Rivers, action of, 47.
of Palezoic origin, 56.
River terraces, 222.
Roches moutonuees, 61, 216.
Rocks, Archaean, 106.
fragmental, 25.
kinds of, 3, 13.
making of, 23, 33, 35, 44.
metamorphic, 26.
of Mississippi valley, 136.
stratified, 19, 21, 25.
thickness of Lower Silurian, 129.
thickness of Paleozoic in North America,
167.
unstratified, 21.
Rocky Mountains, origin of, 193, 206.
Mountain coal-area, 198.
Rotalia, 32.
ST. LAWRENCE River in the Quaternary, 219,
221.
Saliferous group of Britain and Europe, 177-
rocks of New York, 130.
Sali'na rocks, 130.
Salix, Cretaceous, 181.
Salt of Salina and Canada, 130.
of Triassic, 177.
Sand, 15.
Sand-scratches, 46.
Sandstone, 14, 15.
Sapphire, 6.
Sassafras Cretaceum, 181.
Schist, schistose rocks, 16.
Scoria, 19.
Scratches, glacial, 60, 212.
Sea-beaches, elevated, 221.
Sea-saurians, 164, 188.
Sea-weeds, or Algae, 112, 117.
Sediment of Mississippi River, 48.
Sela'chians, 144, 161.
Shale, 14.
Sharks, Devonian. 144.
Carboniferous, 161.
Tertiary, 202.
Upper Silurian, 133.
Shasta, 64.
Shells, rocks made of, 27, 33.
Sid'erite, 12.
SigiUa'ria, Sigillarids, 141, 159.
Silica, or Quartz, 3, 5.
Silicates, 5.
Siliceous plants, 35.
sponges, 39.
Polycistines, 37.
waters of Geysers, 68.
Silurian age, 113.
Lower, 115.
Upper, 129.
Skeletons of man, 231.
Slate, 15.
Sloths, gigantic, of Quaternary, 227.
Sol'fata'ras, 70.
Solidification, 70.
Spathic iron ore, 12.
Species, exterminations of, 127, 173, 240.
Sphagnous mosses, 40.
Sphenopteris Gravenhorstii, 158.
Spicules of Sponges, 37.
Spiders, 100, 162.
Spirifer, 152.
Sponges, 37, 39, 79.
Squid, 185.
Stalactites, 24.
Stalagmite, 24.
containing bones of cave animals, 225, 233.
Stone age, 231.
Strata, definition of, 21.
Stratification, 19.
Strike, 83.
Subcarboniferous period, 150.
Subsidence during the Champlain period, 218,
220.
Sweden, modern change of level in, 237.
Sy'enyte, 17.
Synclinal, 85.
System of life, 242.
TAILS of fishes, 145.
Tapir, 203.
Teliost fishes, 186.
Terrace period. See RECENT PEKIOD.
Terraces along rivers, 221.
Tertiary age, 194.
Time, length of geological, 237, 239.
Trach'yte, 19.
Tracks of reptiles, 187.
Transitions between species, 237.
Trap, 18.
of Connecticut valley, etc., 193.
columnar, 22.
INDEX.
263
Trav'ertine, 24.
Tree-ferns, 157.
Trenton limestone, 117.
Triassic period, 17*.
Tri'lobites, 125, 133, 142, 160.
Tufa, 19.
calcareous, 24.
UNCONFORMABLE strata, 88.
Unstratified rocks, 21.
Uplifts, 89.
Upper Helderberg, 138.
Upper Silurian, 129.
VALLEYS, formation of, 73.
Veins, formation of, 73.
Vertebrates, 110.
Tertiary, 202.
Vesuvius, 67.
Volcanic rocks, 18.
Volcanoes, 64.
WATER, action of fresh, 46.
action of oceanic, 50.
freezing and frozen, 57.
Waves, action of, 51.
Weal'den, 179.
Wenlock limestone, 130.
Whales, first of, 210.
Willow, Cretaceous, 181.
Wind-drift structure, 45.
Wind River Mountains, 107.
Winds, effects of, 44.
White Mountains, glacial scratches on, 213.
alpine plants on, 224.
Wolf, Quaternary, 226.
Worms, 100.
XIPHODON, 204.
YELLOWSTONE Park, 70.
ZEACRINUS elegans, 151.
THE END.
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