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[Illustration: Cape Trinity on the Saguenay. A salient point of
Laurentian Gneiss, on an old fiord of Pliocene erosion (p. 99). (_From a
Photograph by Henderson._)]
SOME SALIENT POINTS
IN THE
SCIENCE OF THE EARTH
BY
SIR J. WILLIAM DAWSON C.M.G., LL.D., F.R.S., F.G.S., &c.
_WITH FORTY-SIX ILLUSTRATIONS_
[Illustration]
NEW YORK
HARPER & BROTHERS PUBLISHERS
1894
PREFACE.
The present work contains much that is new, and much in correction
and amplification of that which is old; and is intended as a closing
deliverance on some of the more important questions of geology, on the
part of a veteran worker, conversant in his younger days with those
giants of the last generation, who, in the heroic age of geological
science, piled up the mountains on which it is now the privilege of
their successors to stand.
J. W. D.
_Montreal_ 1893.
CONTENTS.
CHAPTER I. Page
The Starting-point 3
CHAPTER II.
World-making 9
CHAPTER III.
The Imperfection of the Geological Record 39
CHAPTER IV.
The History of the North Atlantic 57
CHAPTER V.
The Dawn of Life 95
CHAPTER VI.
What May Be Learned from Eozoon 135
CHAPTER VII.
The Apparition and Succession of Animal Forms 169
CHAPTER VIII.
The Genesis and Migrations of Plants 201
CHAPTER IX.
The Growth of Coal 233
CHAPTER X. PAGE
The Oldest Air-breathers 257
CHAPTER XI.
Markings, Footprints, and Fucoids 311
CHAPTER XII.
Pre-determination in Nature 329
CHAPTER XIII.
The Great Ice Age 345
CHAPTER XIV.
Causes of Climatal Change 363
CHAPTER XV.
The Distribution of Animals and Plants As Related
to Geographical and Geological Changes 401
CHAPTER XVI.
Alpine and Arctic Plants in Connection With
Geological History 425
CHAPTER XVII.
Early Man 459
CHAPTER XVIII.
Man in Nature 481
LIST OF ILLUSTRATIONS.
Page
Cape Trinity on the Saguenay _Frontispiece_
Folding of the Earth's Crust _To face_ 9
Cambro-Silurian Sponges " 39
Map of the North Atlantic " 57
Nature-print of Eozoon " 95
Laurentian Hills, Lower St. Lawrence 100
Section from Petite Nation Seigniory to St. Jerome 101
The Laurentian Nucleus of the American Continent 103
Attitude of Limestone at St. Pierre 109
Weathered Eozoon and Canals _To face_ 112
" " " 113
Group of Canals in Eozoon 115
Amœba and Actinophrys 119
Minute Foraminiferal Forms 123
Section of a Nummulite 127
Portion of Shell of Calcarina 128
Weathered Eozoon with Oscular tubes _To face_ 135
Diagram showing different States of Fossilization
of a Cell of a Tabulate Coral 139
Slice of Crystalline Lower Silurian Limestone 141
Walls of Eozoon penetrated with Canals 141
Joint of a Crinoid 145
Shell from a Silurian Limestone, Wales 146
Casts of Canals of Eozoon in Serpentine 147
Canals of Eozoon 147
Primordial Trilobites _To face_ 169
Primitive Fishes " 184
Devonian Forest " 201
Coal Section in Nova Scotia 233
Skeleton of _Hylonomus Lyelli_ _To face_ 257
Footprints of _Hylopus Logani_ " 260
Humerus and Jaws of _Dendrerpeton_ " 272
Reptiliferous Tree " 276
Microsaurian, restored " 278
_Dolichosoma longissimum_, restored " 286
_Pupa_ and _Conulus_ " 288
Millipedes and Insect " 296
Footprints of _Limulus_ " 311
_Rusichnites Grenvillensis_ " 322
Restoration of _Protospongia tetranema_ " 329
Giant Net-sponge " 336
Boulder Beach, Little Metis " 345
Palæogeography of North America " 383
Distribution of Animals in Time " 401
Tuckerman's Ravine and Mount Washington " 425
Pre-historic Skulls " 459
Primitive Sculpture " 481
TABLE OF GEOLOGICAL HISTORY.
Non-Geological readers will find in the following table a condensed
explanation of the more important technical terms used in the following
pages. The order is from older to newer.
GREATER SYSTEMS OF CHARACTERISTIC FOSSILS.
PERIODS. FORMATIONS.
Archæan or Eozoic
Pre-Laurentian
Laurentian Protozoa Protophyta
Palæozoic
Huronian { Crustaceans Algæ
Cambrian { Molluscs Cryptogamous
Cambro-Silurian[A] { Worms and
Silurian[B] { Corals, etc, Gymnospermous
Devonian Fishes Plants.
Carboniferous Amphibians
Permian
Mesozoic
Triassic { Reptiles Pines and
Jurassic { Birds Cycads
Cretaceous { Earliest Mammals. Trees of modern
types.
Kainozoic or Tertiary
Eocene Higher Mammals
Miocene of extinct forms
Pliocene Recent Mammals Modern Plants,
Pleistocene and
Modern Man.
[A] Ordovician of Lapworth.
[B] Salopian of Lapworth.
_THE STARTING-POINT._
DEDICATED TO THE MEMORY OF
PROF. ROBERT JAMESON,
Of the University of Edinburgh, my first Teacher in Geology,
whose Lectures I attended, and whose kind Advice and
Guidance I enjoyed, in the Winter of 1840-1841.
Headlands and Spurs--Popular Papers on Leading Topics--Revisiting Old
Localities--Dedications--General Scope of the Work
CHAPTER I.
_THE STARTING-POINT._
An explorer trudging along some line of coast, or traversing some
mountain region, may now and then reach a projecting headland, or bold
mountain spur, which may enable him to command a wide view of shore
and sea, or of hill and valley, before and behind. On such a salient
point he may sit down, note-book and glass in hand, and endeavour to
correlate the observations made on the ground he has traversed, and
may strain his eyes forward in order to anticipate the features of
the track in advance. Such are the salient points in a scientific
pilgrimage of more than half a century, to which I desire to invite
the attention of the readers of these papers. In doing so, I do not
propose to refer, except incidentally, to subjects which I have already
discussed in books accessible to general readers, but rather to those
which are imbedded in little accessible transactions, or scientific
periodicals, or which have fallen out of print. I cannot therefore
pretend to place the reader on all the salient points of geological
science, or even on all of those I have myself reached, but merely to
lead him to some of the viewing-places which I have found particularly
instructive to myself.
For similar reasons it is inevitable that a certain personal element
shall enter into these reminiscences, though this autobiographical
feature will be kept as much in the background as possible. It is
also to be anticipated that the same subject may appear more than
once, but from different points of view, since it is often useful to
contemplate certain features of the landscape from more than one place
of observation.
To drop the figure, the reader will find in these papers, in a plain
and popular form, yet it is hoped not in a superficial manner, some
of the more important conclusions of a geological worker of the old
school, who, while necessarily giving attention to certain specialties,
has endeavoured to take a broad and comprehensive view of the making of
the world in all its aspects.
The papers are of various dates; but in revising them for publication
I have endeavoured, without materially changing their original form,
to bring them up to the present time, and to state any corrections or
changes of view that have commended themselves to me in the meantime.
Such changes or modifications of view must of necessity occur to every
geological worker. Sometimes, after long digging and hammering in some
bed rich in fossils, and carrying home a bag laden with treasures, one
has returned to the spot, and turned over the _débris_ of previous
excavation, with the result of finding something rare and valuable,
before overlooked. Or, in carefully trimming and chiselling out the
matrix of a new fossil, so as to uncover all its parts, unexpected
and novel features may develop themselves. Thus, if we were right or
partially right before, our new experience may still enable us to
enlarge our views or to correct some misapprehensions. In that spirit
I have endeavoured to revise these papers, and while I have been able
to add confirmations of views long ago expressed, have been willing to
accept corrections and modifications based on later discoveries.
In the somewhat extended span of work which has been allotted to me,
I have made it my object to discover new facts, and to this end have
spared no expenditure of time and labour; but I have felt that the
results of discoveries in the works of God should not be confined to a
coterie, but should be made public for the benefit of all. Hence I have
gladly embraced any opportunities to popularise my results, whether in
lectures, articles, popular books, or in the instruction of students,
and this in a manner to give accurate knowledge, and perhaps to attract
the attention of fellow-workers to points which they might overlook if
presented merely in dry and technical papers. These objects I have in
view in connection with the present collection of papers, and also the
fact that my own pilgrimage is approaching its close, and that I desire
to aid others who may chance to traverse the ground I have passed over,
or who may be preparing to pass beyond the point I have reached.
To a naturalist of seventy years the greater part of life lies in the
past, and in revising these papers I have necessarily had my thoughts
directed to the memory of friends, teachers, guides, and companions in
labour, who have passed away. I have therefore, as a slight token of
loving and grateful remembrance dedicated these papers to the memory
of men I have known and loved, and who, I feel, would sympathise with
me in spirit, in the attempt, however feeble, to direct attention to
the variety and majesty of those great works of the Creator which they
themselves delighted to study.
Since the design of these papers excludes special details as to
Canadian geology, or that of those old eastern countries to which I
have given some attention, I must refer for them to other works, and
shall append such reference of this kind as may be necessary. At the
same time it will be observed that as my geological work has been
concerned most largely with the oldest and newest rocks of the earth,
and with the history of life rather than with rocks and minerals, there
must necessarily be some preponderance in these directions, which might
however, independently of personal considerations, be justified by
the actual value of these lines of investigation, and by the special
interest attaching to them in the present state of scientific discovery.
Having thus defined my starting-point, I would now with all respect and
deference ask the reader to accompany me from point to point, and to
examine for himself the objects which may appear either near, or in the
dim uncertain distance, in illustration of what the world is, and how
it became what it is. Perhaps, in doing so, he may be able to perceive
much more than I have been able to discover; and if so, I shall
rejoice, even if such further insight should correct or counteract
some of my own impressions. It is not given to any one age or set of
men to comprehend all the mysteries of nature, or to arrive at a point
where it can be said, there is no need of farther exploration. Even in
the longest journey of the most adventurous traveller there is an end
of discovery, and, in the study of nature, cape rises beyond cape and
mountain behind mountain interminably. The finite cannot comprehend
the infinite, the temporal the eternal. We need not, however, on that
account be agnostics, for it is still true that, within the scope of
our narrow powers and opportunities, the Supreme Intelligence reveals
to us in nature His power and divinity; and it is this, and this alone,
that gives attraction and dignity to natural science.
_WORLD-MAKING._
DEDICATED TO THE MEMORY OF
ADAM SEDGWICK AND SIR RODERICK IMPEY MURCHISON,
Whose joint Labours carried
our Knowledge of the History of the Earth
two Stages farther back,
and whose Differences of Opinion served to
render more glorious their Victories.
[Illustration: Fig. 1. Diagram illustrating Folding of the Crust
of the Earth.--(_a_) Undisturbed crust. (_b_) Primary depression
and deposition. (_c_) Mountain-making folds with their relations
to an upper and lower magma. Fig. 2. Result of folding, faulting,
and denudation, as seen at Cascade Mountain, Western Canada (after
McConnell, p. 33).]