Nature, ā the first mentioned being the infcrio)-, the other the superior. The
latter is also the more typical group, or that in which the idea of the type is
more fully represented : ā
o. Life in general. ā (1.) Vegetable kingdom; (2.) Animal kingdom.
h. Vecjetahle kingdom. ā (1,) Cryptogams, or flowerless plants; (2.) Phaeno-
gams, or flowering plants.
c. Animal kingdom. ā (1.) The flower-like type, including Radiates; (2.) the
true Animal type, or cephalized species, that is, those having a head (or ante-
rior and posterior polarity with bilateral symmetry), including Mollusks, Arti-
culates, and Vertebrates.
d. Siib-ldngdom of Jfollusks. ā (1.) The flower-like type, including the Bryo-
zoans, closely like flowers, the Brachiopods, which also in general were attached
below by stems or pedicels, and Ascidians, also, often attached and many
radiated exteriorly ; (2.) the true Molluscan type, including Acephals, Cepha-
lates, and Cephalopods.
e. Sab-kingdom of Vertebrates. ā (1.) Water-vertebrates, including Fishes; (2.)
Land-vertebrates, including Reptiles, Birds, and Mammals.
/. Class of Crustaceans. ā (1.) EiTtomostracans ; (2.) Malacostracans.
g. Class of Rejitiles. ā (1.) Amphibians; (2.) True Reptiles (p. 344).
h. Class of Mammals. ā (1.) Marsupials, or Semi-oviparans ; (2.) Non-marsu-
pials, or typical Mammals (p. 423).
^ 1. Life ix general. ā In the inferior subdivision the earliest species of life
were probably the Protopliytes, ā these and other Algae commencing in the later
Azoic. They have the locomotive powers of animals, and may therefore be
regarded as an example of one of the comprehensive types, and the first. The
Protozoans (Rhizopods, etc.) may have been the associated species of the suj^erior
group, as remarked on page 147. The two are alike in extreme simplicity of
organization. In Algae the Radiate type of structure, characteristic of the typi-
cal plant, is not brought out; and in Protozoans neither of the four great
Animal types appears, ā the Radiate, Molluscan, Articulate, or Vertebrate.
PROGRESS OF LIFE. 597
ā¢
If, therefore, these simple species existed in the Azoic era, they were system-
less life, and only foreshadowed the great systems of life which were after-
wards displayed according to their respective types in the true Zoic ages.
2. Kingdoms. ā (o.) Vetjctahlc. ā The earliest Land-plants included Acrogens
or the superior Cryptogams, and Conifers or the inferior Phsenogams ; and
among them there were the intei'mediate comprehensive types of Lepidoden-
drids, Calamites, and Sigillarids. See p. 283.
(?>.) Animal. ā Among the earliest of Animals in the Primordial there were the
Cystids (Crinoids). These belong to the Echinoderms, which make the upper por-
tion of the inferior subdivision of animals j and they are a comprehensive type
between Radiates and Mollusks (the lower portion of the superior subdivision).
Some early kinds have almost the same absence of symmetry in the body that
belongs to Mollusks, and are furnished with only two arms. The associated
siqjerior species were Mollusks and Articulates ; and the earliest Mollusks, the
Lingulas, and others among Brachiopods, stood on a stem like the Cystids, and
had also two arms.
3. Sub-kingdoms. ā (a,) Mollusks. ā The Mollusks of the earliest or Primordial
period were from the higher group of the inferior division, that is, the Brachio-
pods. The associated superior species comprised Cephalates before Acephals, ā
that is, the middle before the inferior group.
(6.) Vertchrates. ā The earliest Vertebrates were of the inferior subdivision,
or that of Fishes, and from its upper portion, ā that is, the orders of Ganoids
and Selachians. The Ganoids were a comprehensive type foreshadowing
the lower group of the sujyerior division of Vertebrates, ā that is. Reptiles
(p. 302), which group did not make its appearance until the close of another
age.
4. Classes. ā {a.) Gi/mnospenns in the Vcrjetahle kinfjdom. ā The group of Cy-
cads is one of the most marked of comprehensive types, as explained on
page 418.
(6.) Crustaceans. ā The earliest Crustaceans, commencing even in the lowest
Primordial, were Trilobites, ranking with the highest of Entomostracans, or
the inferior subdivision, or even above their true level. They constitute a com-
prehensive type, foreshadowing the Tetradecapods, which are not known to
have appeared before the Carboniferous age (p. 375). There was also another
comprehensive type in the same early strata, ā the Phyllopods, foreshadowing
the still higher division of Decapods, which appeared under the form of Macrou-
rans at the same time.
(c.) Reptiles. ā Among the earliest Reptiles in the Carboniferous age there
were the Labyrinthodonts, ā the highest of the inferior division, a comprehensive
type having many characteristics of true Reptiles (p. 345). The associated
species were other Amphibians; also species of the lower groups of the
snjyerior division, ā that is, the lower Lacertians and Swimming Saurians
(p. 351).
((/.) 3fammals. ā The earliest Mammals were Marsupials of the inferior sub-
division, and Insectivores of the superior; and the order of Insectivores is a
typical one among the lower superior. See, further, Appendix F.
598 HISTORICAL GEOLOGY.
8. Comprehensive types generally hecoiyiing nearly or quite extinct in the
course of future progress. ā See page 397 for illustrations.
9. Unity in the successive Floras and Faunas of the ages. ā The unity
or harmonious character of the Flora of the Carboniferous age, and
the dependence of this unity on the principle just explained, is the
subject of remark on page 396. It is a marked feature of each of
the ages.
If the view of the Azoic age given on page 596 is right, this unity was
strikingly brought out in the first expression of life. In the Primordial life this
unity is equally marked. There' were Brachiopods on stems, associated with the
unsymmetrical Cystids, also on stems, and more flower-like ; ā and, with these
sedentary species, the Trilobite, nearly as sedentary in habit, ā for it seems to
have clung to any supporting surface, like a limpet, though capable of swimming
off or crawling over the sea-bottom. The Gasteropods, Pteropods, and Phyllo-
pods were the more active species. A little later, before the close of the Pri-
mordial period, there were bivalve Crustaceans in harmony with the bivalve
Brachiopods. There was also a new type, indicating progress, in the large and
active Cephalopods, the Orthocerata, etc.
The same general features continued to characterize the Lower and Upper
Silurian, only with additions to the flower-like animals in Corals, Crinoids,
and Bryozoans, and an increase in the diversity of Brachiopods and Trilo-
bites. The unity also appears in the simplicity of structure of the several types.
In the Mesozoic Fauna there was also a wonderful harmony, as explained
on page 501. In the Mesozoic Flora there was a unity as striking as in
the Carboniferous. Conifers, Tree-ferns, and Cycads made up the bulk of
the trees, and the last type, while fundamentally related to the Conifers,
partook somewhat of the character of the Tree-fern in its mode of growth.
At the same time, this comprehensive type had some characteristics of the
palm, ā the type it foreshadowed, and which, before the close of the Mesozoic,
was already in the forests along with the highest type of plants, the An-
giosperms.
10. Progress always an unfolding of a type or an exhibition of it in its
possible diversities, and involving the introduction of inferior as well as supe-
rior species. ā It has been already shown that the progress was not a
lineal upward progress. The facts with regard to comprehensive
types and the associated species throw this principle into a strong
light ; for these species occupy nodal points, as they may be called,
or points of divarication, far remote in most cases from the lowest
species of a group.
The progress was not necessarily attended with much rise in
grade. The earliest fishes are of the highest orders in that class.
These orders undergo some little elevation in after-time ; but in the
introduction of the Teliosts, or common fishes, in which the great
expansion ultimately takes place, there is a fall below the level of
the early orders.
PROGRESS or LIFE. 699
In all cases, however, there was an unfolding of a type, ā an exhi-
bition of it through the successive appearance of new groups, in which
groups characteristics before only foreshadowed, or existing only in
potentiality, come out into full expression. The early general or com-
prehensive type thus becomes in a sense specialized, or represented
in numbers of special groups. In the case of Fishes, the type, when
the Teliosts appeared, came forth in its purity, dej)rived of the
Eeptilian features of the Ganoids (marked in their vertebrae, teeth,
air-bladder, and other parts) and developed in those points which
make up the true Fish. Moreover, the Fish-type was at the same
time represented under a diversity of tribes, and an extraordinary
variety of shapes, normal and abnormal, high and low (some almost
of the low grade of a Polyp), which was in great contrast with the
uniformity of structure and limited variation of form in the Ga-
noids. Nature thus revels in exuberance when displaying a tyj^e
after its true level is attained.
In this kind of progress there is naturally expansion towards
inferior as well as superior grades : it is not out of harmony with
the systein that Echinoderms should have existed before Polyps,
Tree-ferns and Lepidodendrids before Mosses, Lacertians and
Crocodiles before Snakes, or Herbivores and- Carnivores before
Sloths.
When a type had passed its culmination, there was sometimes a
.very marked decline in the character of the species that preceded its
final extinction. Examples of this have been referred to in the
last of the LeptccncB. that occurred in the Mesozoic (p. 450), and the
multiplication of uncoiled forms of the Ammonite family which
took place in the Cretaceous (p. 472).
This law of specialization ā the general before the special ā is the
^lawof.all development. The egg is at first a simple unit; and,
gradually, part after part of the new structure is evolved, that which
is most fundamental appearing earliest, until the being is complete
in all its oviter and minor details. The principle is exhibited in the
physical history of the globe, ā which was first a featureless globe of
fire, then had its oceans and dry land, in course of time received
mountains and rivers, and finally all those diversities of surface
which now characterize it. Again, the climates began with uni-
versal tropics ; gradually, zones were apparent ; and at last the
diversity of the present day.
But there is a wide distinction in the kind of specialization which
starts from a simple unit like an egg, and that proceeding from com-
prehensive types among plants and animals. Tlie one is diversity
out of memberless simplicity ; the other, diversity from a unit of
600 HISTORICAL GEOLOGY.
comiDlex structure. The latter is simply an exhibition of the gene-
ral law of succession in the creations by which the system of life
reached its completion.
2. Eelation of the History of Life to the Physical History of the
Globe.
1. The plan of progress was determined with reference to the last age, with
all its diversities of climate, continental surfaces and oceans, as its era of
fullest exhibition.
2. The progress in climate and other conditions involved a concurrent pro-
gress from the inferior liviyig species to the superior, ā The existence of a
long marine era, through the Silurian and part of the Devonian
ages, admitted only of the existence of marine life. Hence the
dominant type of the Silurian was the Molluscan, which, with the
Radiate, is eminently marine. In addition, there were marine Arti-
culates and marine plants ; and when the Vertebrates began it was
with marine species, the Fishes. Thus the prevalence of waters
involved inferiority of species. The increase of land, gradual purifi-
cation of the atmosphere, and cooling of the globe, prepared the way
for the higher species.
It is probable that the oceanic waters were also in an impure state
compared with the present, from containing an excess of salts of
lime ; and this also involved the existing of inferior species, ā such
as Crinoids, Corals, and MoUusks, a very large proportion of whose
weight is in calcareous material. The removal of this excess of
lime from the waters produced limestone strata, purified the
waters, and fitted the oceans for other species.
The great prevalence, in the Primordial, of Lingulse (whose shells contain a
large amount of ijhosphate of lime) is further evidence of the greater density
of the waters, and seems to indicate the presence of an excess of phosphates.
3. The progress in climate and in the condition of the atmosphere and waters
involved a localization of tribes in time, or chronographically , just as they are
now localized by climate over the eartKs surface, or geographically . ā Tribes
were made for a special climate or condition of the globe ; and when
this climate or condition had been passed in the earth's progress,
the tribes no longer existed. The culmination of the Reptilian
and Molluscan types in the Reptilian age, or of Trilobites and
Brachiopods in Palaeozoic time, are examples. The former when in-
stituted had those special relations to climate that made the Repti-
lian age the era of their culmination ; just as now palms and bananas
reach their perfection only in the equatorial zone ; figs in the
PROGRESS OF LIFE. 601
tropical ; myrtles and laurels, in the sub-tropical ; evergreen trees,
in the warm-temperate ; ordinary deciduous trees, in the cold-tem-
perate ; and pines, in the sub-arctic. As there are now these zones
on going from the equator to the poles, so there were successive eras
passed over from the Silurian ā the period of universal warm tempe-
rature ā to the present age of a frigid arctic, and a mean temperature
of 58Ā° to 60Ā° F. Climate may not have been the only cause ; but it
was one, and of great importance. The Crustacean type is one of
those which have culminated in the age of Man ; and this accords
with the fact that its highest species ā the Maioids, or Triangular
Crabs ā are now most numerous and of the highest rank in the
colder temperate zone. It was made to reach its maximum in a
cold climate, and therefore in the existing age.
No species survived through all time, and few through two suc-
cessive periods. The oldest now existing began in the Middle Ter-
tiary, and these were only Invertebrates. The oldest quadruped
dates no farther back than the Post-tertiary.
But two genera range through the Avhole series of ages from the
first or Potsdam epoch, ā Lingula and Discina, ā enough to manifest
the oneness of system from the beginning. There was in general a
changing of genera with the successive periods. Even tribes wholly
disappeared from age to age, as the world outgrew them. Of Trilo-
bites, 500 species once lived, of the Ammonite group, 900 species,
all of which are extinct; the Nautilus tribe, 450 ; three or four spe-
cies are all that exist. Of Ganoid fishes, 700 species have been dis-
covered ; the tribe is now nearly extinct. Thus, the old has passed
away as the new has come in. Remains of nearly 40,000 animal
species have been gathered from the rocks, all of which are ex-
tinct ; and, considering how few of the whole number would have
become fossilized, this can hardly be one-tenth of the number that
have existed and are gone. 2500 extinct species of plants have
been found, ā which cannot be over a twentieth of all that have
covered the earth in its former ages.
4. The extermination of species was in general due to catastrophes, lohile
the extinction of tribes or higher groups may have been a consequence of secu-
lar changes in the condition of the climate, atmosphere, or waters. ā The ex-
termination of species here alluded to, and some of the kinds of
catastrophes which caused them, are briefly considered on p. 398.
5. With regard to the Origination of Species, Geology suggests no
theory of natural forces. It is right for science to search out Na-
ture's methods, and strive to employ her forces ā organic or inor-
ganic ā in the effort, vain though it prove, to derive thence new
living species. The study of fossils has given no aid in this direc-
602 HISTORICAL GEOLOGY.
tion. It has brought to light no facts sustaining a theory that
derives species from others, either by a system of evolution, or by a
system of variations of living individuals, and bears strongly against
both hypotheses. There are no lineal series through creation cor-
responding to such methods of development. Instead of grada-
tions from Mollusks or Articulates to the lower Fishes, and so on
upward, the Fish-type commences near its summit-level, or rather
between the level of the typical fish and that of a higher class of
Vertebrates. Were either of these plans the system in nature,
examples of the blending of species would be common through all
the classes, high and low ; and North America would afford them
as successive stages between the old Elephant or Mastodon and
earlier species, and so throughout the various tribes of life, animal
and vegetable. But, in fact, appearances suggesting the idea of
such shadings among species are exceedingly rare, ā wonderfully so,
considering that Palaeontology has only the imperfect stony secre-
tions of animals to study out, which sometimes afford insufficient
distinctions even when perfect and from living species. Under
any scheme of development of species from species, the system of
life, after ages of progress, would have become a blended mass,
ā the temple of nature fused over its surface and throughout its
structure. The study of the past has opened to view no such
result.
Geology appears to bring us directly before the Creator ; and,
while opening to us the methods through which the forces of na-
ture have accomplished His purpose, ā while proving that there has
been a plan glorious in its scheme and perfect in system, progress-
ing through unmeasured ages and looking ever towards Man and
a spiritual end, ā it leads to no other solution of the great problem
of creation, whether of kinds of matter or of species of life, than
this : ā
Deus fecit.
PART IV.
DYNAMICAL GEOLOGY.
Dynamical Geology treats of the causes of events in the earth's
geological progress.
These events include ā the formation of all rocks, stratified and
unstratified, with whatever they contain, from the earliest Azoic to
the modern beds of gravel, sand, clays, and lavas ; the oscillations
of the earth's crust ; the increase of dry land, elevation of moun-
tains, and elimination of the surface-features of the globe ; the
changes of climate ; the changes of life.
The causes or agencies, exclusive of life, that have been engaged
have acted for the most part through the atmosphere, waters, and
rock-material. But they are based necessarily on the general
powers of Nature, ā Heat, Light, Electricity, and Attraction. These
fundamental powers have their universal laws, ā as the law of
gravitation, according to which falling bodies move; the laws of
chemical attraction, according to which comj^ounds are formed
and decompositions take place ; the laws of cohesion or crystalliza-
tion, according to which solidification produces crystals, or a crys-
talline structure ; the laws of heat, as regards conduction, expan-
sion, etc., and the influence of heat on chemical changes and
growth ; the laws of light, as to its nature, and its action in chemi-
cal changes and growth, etc. ; the laws of electricity and mag-
netism : all of which the geologist cannot understand too well.
But the discussion of these topics belongs properly to a treatise on
Physics. The laws of solidification are, however, briefly considered
in this place, on account of their bearing on the structure of rocks.
In addition to the general operation of forces, there are other
actions, that may be embraced under the term dimatological, which
proceed from the systematic arrangement and movement of heat,
light, moisture, and electricity about the sphere (causing zones of
temperature, varieties of climate, etc.), and also from the systems
603
604 DYNAMICAL GEOLOGY.
of atmospheric and oceanic circulation. The general facts on these
topics are briefly stated on pp. 39-48, which may well be reviewed
before proceeding Avith the following pages. In treatises on Physi-
cal Geography these subjects may be studied to greater length by
the geological student with much advantage.
The subject of dynamics, or the causes or agencies in geological
history, is here treated under the following heads : ā
1. Life as an agent in protecting, destroying, and making rocks.
2. Cohesive attraction, with reference especially to crystallization
and the concretionary structure.
3. The Atmosphere, as a mechanical agent.
4. Water, as a mechanical agent.
5. Heat, as an agent in producing volcanic phenomena, non-vol-
canic igneous eruptions, metamorphism, veins, etc.
6. Movements in the earth's crust, and their consequences,
including the plication of strata, origin of mountains, earthquakes,
and the evolution of the general features of the globe.
7. The chemistry of rocks, or the chemical processes concerned
in their origin and metamorphism, embracing a consideration of
Life, the Atmosphere, Water and Heat as chemical agents. This
dej^artment of the science is often called Chemical Geology. As
its proper elucidation would require a large amount of space, and
its study a minute knowledge of the details of Chemistry, the sub-
ject is not taken up in this Manual.
I. LIFE.
1. Protective Effects.
The protective effects of life come almost solely from vegetation.
1. Turf protects earthy slopes from the wearing action of rills
that would gully out a bare surface ; and even hard rocks receive
protection in the same way.
2. Tufts of grass and other plants over sand-hills, as on sea-shores,
bind down the moving sands.
3. Lines of vegetation along the banks of streams prevent wear
during freshets. When the vegetation consists of shrubs or trees,
the stems and trunks entangle and detain detritus and floating
wood, and serve to increase the height of the margin of the
stream.
4. Vegetation on the borders of a pond or bay serves in a similar
manner as a protection against the feebler wave-action. In many
LIFE. 605
tropical regions, plants growing at the water's edge, like the man-
grove, drop new roots from the branches into the shallow water,
which act like a thicket of brush-wood to retain the floating leaves,
stems and detritus; and, as the water shallows, other roots are
droj^ped farther out, which are attended with the same effect ; and
thus they keep moving outward, and subserve the double purpose
of protecting and making land.
5. Patches of forest-trees on the declivities in Alpine valleys
serve to turn the course of the descending avalanche, and entangle
snows that, but for the presence of the trees, would only add to its
extent ; and in the Alps such groves, wherever existing, are usually
guarded from destruction with great care.
2. Transporting Effects.
1. Seeds are often caught in the hair or fur of animals, and thus
transported from place to place.
2. Seeds are eaten by animals as food, or in connection with their
food, which sometimes pass out undigested, and become planted in
a new region ; and, in the case of birds on their migration, they
may be carried far from the place where gathered.
3. Ova of fish, reptiles, and inferior animals are supposed to be
transferred from one region to another by birds and other animals.
Authenticated instances of this are wanting.
4. Snails and fresh-water shells are often floated off on logs or
floating plants, and sometimes are carried into estuaries or the sea,
and so become mingled with marine shells.
5. Migrating tribes of men carry in their grain, or otherwise, the
seeds of various Aveeds, and also, involuntarily, rats, mice, cock-
roaches, and smaller vermin. The origin of tribes may often be
inferred from the species of plants and of domesticated and other
animals found to have accomj)anied them.
3. Destructive Effects.
The destructive effects proceed either from living plants or ani-
mals, or from the products of decomposition.