Transcriber Notes
Text emphasis denoted as _Italics_.
[Illustration:
Plate I.
From a Photo. by Henderson Vincent Brooke, Day & Son. Lith.
CAPE TRINITY ON THE SAGUENAY.
A CLIFF OF LAURENTIAN GNEISS.
_Frontispiece_]
LIFE'S DAWN ON EARTH:
BEING THE
History of the Oldest Known Fossil Remains,
AND
THEIR RELATIONS TO GEOLOGICAL TIME
AND TO THE DEVELOPMENT OF
THE ANIMAL KINGDOM.
BY
J. W. DAWSON, LL.D., F.R.S., F.G.S., Etc.,
PRINCIPAL AND VICE-CHANCELLOR OF M'GILL UNIVERSITY, MONTREAL;
AUTHOR OF
"ARCHAIA," "ACADIAN GEOLOGY," "THE STORY OF
THE EARTH AND MAN," ETC.
_SECOND THOUSAND._
LONDON:
HODDER & STOUGHTON,
27, PATERNOSTER ROW.
MDCCCLXXV.
Butler & Tanner,
The Selwood Printing Works,
Frome, and London.
To the Memory of
SIR WILLIAM EDMOND LOGAN,
LL.D., F.R.S., F.G.S.,
THIS WORK IS DEDICATED,
Not merely as a fitting acknowledgment of his long and successful
labours in the geology of those most ancient rocks, first named by
him Laurentian, and which have afforded the earliest known traces
of the beginning of life, but also as a tribute of sincere personal
esteem and regard to the memory of one who, while he attained to the
highest eminence as a student of nature, was also distinguished by his
patriotism and public spirit, by the simplicity and earnestness of his
character, and by the warmth of his friendships.
PREFACE.
An eminent German geologist has characterized the discovery of fossils
in the Laurentian rocks of Canada as "the opening of a new era in
geological science." Believing this to be no exaggeration, I have
felt it to be a duty incumbent on those who have been the apostles of
this new era, to make its significance as widely known as possible to
all who take any interest in scientific subjects, as well as to those
naturalists and geologists who may not have had their attention turned
to this special topic.
The delivery of occasional lectures to popular audiences on this and
kindred subjects, has convinced me that the beginning of life in the
earth is a theme having attractions for all intelligent persons;
while the numerous inquiries on the part of scientific students with
reference to the fossils of the Eozoic age, show that the subject
is yet far from being familiar to their minds. I offer no apology
therefore for attempting to throw into the form of a book accessible
to general readers, what is known as to the dawn of life, and cannot
doubt that the present work will meet with at least as much acceptance
as that in which I recently endeavoured to picture the whole series of
the geological ages.
I have to acknowledge my obligations to Sir W. E. Logan for most
of the Laurentian geology in the second chapter, and also for the
beautiful map which he has kindly had prepared at his own expense as
a contribution to the work. To Dr. Carpenter I am indebted for much
information as to foraminiferal structures, and to Dr. Hunt for the
chemistry of the subject. Mr. Selwyn, Director of the Geological
Survey of Canada, has kindly given me access to the materials in its
collections. Mr. Billings has contributed specimens and illustrations
of Palæozoic Protozoa; and Mr. Weston has aided greatly by the
preparation of slices for the microscope, and of photographs, as well
as by assistance in collecting.
J. W. D.
McGill College, Montreal.
_April, 1875._
CONTENTS.
PAGE
Chapter I. Introductory 1
Chapter II. The Laurentian System 7
Notes:--Logan on Structure of Laurentian; Hunt
on Life in the Laurentian; Laurentian Graphite;
Western Laurentian; Metamorphism 24
Chapter III. The History of a Discovery 35
Notes:--Logan on Discovery of Eozoon, and on
Additional Specimens 48
Chapter IV. What is Eozoon? 59
Notes:--Original Description; Note by Dr. Carpenter;
Specimens from Long Lake; Additional
Structural Facts 76
Chapter V. Preservation of Eozoon 93
Notes:--Hunt on Mineralogy of Eozoon; Silicified
Fossils in Silurian Limestones; Minerals
associated with Eozoon; Glauconites 115
Chapter VI. Contemporaries and Successors 127
Notes:--On Stromatoporidæ; Localities of Eozoon 165
Chapter VII. Opponents and Objections 169
Notes:--Objections and Replies; Hunt on
Chemical Objections; Reply by Dr. Carpenter 184
Chapter VIII. The Dawn-Animal as a Teacher in Science 207
Appendix 235
Index 237
LIST OF ILLUSTRATIONS.
FULL PAGE ILLUSTRATIONS.
TO FACE
PAGE
I. Cape Trinity, from a Photograph (_Frontispiece_).
II. Map of the Laurentian Region on the River Ottawa 7
III. Weathered Specimen of Eozoon, from a Photograph 35
IV. Restoration of Eozoon 59
V. Nature-print of Eozoon 93
VI. Canals of Eozoon, Magnified, from Photographs 127
VII. Nature-print of Large Laminated Specimen 169
VIII. Eozoon With Chrysotile, etc. 207
WOODCUTS.
FIG. PAGE
1. General Section 9
2. Laurentian Hills 11
3. Section of Laurentian 13
4. Laurentian Map 16
5. Section at St. Pierre 22
6. Sketch of Rocks at St. Pierre 22
7. Eozoon from Burgess 36
8, 9. Eozoon from Calumet 39
10. Canals of Eozoon 41
11. Nummuline Wall 43
12. Amœba 60
13. Actinophrys 60
14. Entosolenia 62
15. Biloculina 62
16. Polystomella 62
17. Polymorphina 63
18. Archæospherinæ 67
19. Nummulites 73
20. Calcarina 73
21. Foraminiferal Rock-builders 75
21_a_. Casts of Cells of Eozoon 92
22. Modes of Mineralization 96
23. Silurian Organic Limestone 98
24. Wall of Eozoon Penetrated with Canals 98
25. Crinoid Infiltrated with Silicate 103
26. Shell Infiltrated with Silicate 104
27. Diagram of Proper Wall, etc. 106
28, 29. Casts of Canals 107
30. Eozoon from Tudor 111
31. Acervuline Variety of Eozoon 135
32, 33, 34. Archæospherinæ 137, 138
35. Annelid Burrows 140
36. Archæospherinæ 148
37. Eozoon Bavaricum 149
38, 39, 40. Archæocyathus 152, 153
41. Archæocyathus (Structure of) 154
42. Stromatopora 157
43. Stromatopora (Structure of) 158
44. Caunopora 159
45. Cœnostroma 160
46. Receptaculites 162
47, 48. Receptaculites (Structure of) 163
49. Laminæ of Eozoon 176
THE DAWN OF LIFE.
CHAPTER I.
INTRODUCTORY.
Every one has heard of, or ought to have heard of, _Eozoon Canadense_,
the Canadian Dawn-animal, the sole fossil of the ancient Laurentian
rocks of North America, the earliest known representative on our planet
of those wondrous powers of animal life which culminate and unite
themselves with the spirit-world in man himself. Yet few even of those
to whom the name is familiar, know how much it implies, and how strange
and wonderful is the story which can be evoked from this first-born of
old ocean.
No one probably believes that animal life has been an eternal
succession of like forms of being. We are familiar with the idea that
in some way it was introduced; and most men now know, either from the
testimony of Genesis or geology, or of both, that the lower forms
of animal life were introduced first, and that these first living
creatures had their birth in the waters, which are still the prolific
mother of living things innumerable. Further, there is a general
impression that it would be the most appropriate way that the great
procession of animal existence should commence with the humblest types
known to us, and should march on in successive bands of gradually
increasing dignity and power, till man himself brings up the rear.
Do we know the first animal? Can we name it, explain its structure,
and state its relations to its successors? Can we do this by inference
from the succeeding types of being; and if so, do our anticipations
agree with any actual reality disinterred from the earth's crust? If we
could do this, either by inference or actual discovery, how strange it
would be to know that we had before us even the remains of the first
creature that could feel or will, and could place itself in vital
relation with the great powers of inanimate nature. If we believe in a
Creator, we shall feel it a solemn thing to have access to the first
creature into which He breathed the breath of life. If we hold that all
things have been evolved from collision of dead forces, then the first
molecules of matter which took upon themselves the responsibility of
living, and, aiming at the enjoyment of happiness, subjected themselves
to the dread alternatives of pain and mortality, must surely evoke
from us that filial reverence which we owe to the authors of our own
being, if they do not involuntarily draw forth even a superstitious
adoration. The veneration of the old Egyptian for his sacred animals
would be a comparatively reasonable idolatry, if we could imagine any
of these animals to have been the first that emerged from the domain
of dead matter, and the first link in a reproductive chain of being
that produced all the population of the world. Independently of any
such hypotheses, all students of nature must regard with surpassing
interest the first bright streaks of light that break on the long reign
of primeval night and death, and presage the busy day of teeming animal
existence.
No wonder then that geologists have long and earnestly groped in the
rocky archives of the earth in search of some record of this patriarch
of the animal kingdom. But after long and patient research, there still
remained a large residuum of the oldest rocks, destitute of all traces
of living beings, and designated by the hopeless name "Azoic,"--the
formations destitute of remains of life, the stony records of a
lifeless world. So the matter remained till the Laurentian rocks of
Canada, lying at the base of these old Azoic formations, afforded
forms believed to be of organic origin. The discovery was hailed
with enthusiasm by those who had been prepared by previous study to
receive it. It was regarded with feeble and not very intelligent faith
by many more, and was met with half-concealed or open scepticism by
others. It produced a copious crop of descriptive and controversial
literature, but for the most part technical, and confined to scientific
transactions and periodicals, read by very few except specialists.
Thus, few even of geological and biological students have clear ideas
of the real nature and mode of occurrence of these ancient organisms,
and of their relations to better known forms of life; while the crudest
and most inaccurate ideas have been current in lectures and popular
books, and even in text-books, although to the minds of those really
acquainted with the facts, all the disputed points have long ago been
satisfactorily settled, and the true nature and affinities of Eozoon
are distinctly and satisfactorily understood.
This state of things has long ceased to be desirable in the interests
of science, since the settlement of the questions raised is in the
highest degree important to the history of life. We cannot, it is true,
affirm that Eozoon is in reality the long sought prototype of animal
existence; but it is for us at present the last organic foothold, on
which we can poise ourselves, that we may look back into the abyss
of the infinite past, and forward to the long and varied progress of
life in geological time. Its consideration, therefore, is certain,
if properly entered into, to be fruitful of interesting and valuable
thought, and to form the best possible introduction to the history of
life in connection with geology.
It is for these reasons, and because I have been connected with this
great discovery from the first, and have for the last ten years given
to it an amount of labour and attention far greater than could be
adequately represented by short and technical papers, that I have
planned the present work. In it I propose to give a popular, yet
as far as possible accurate, account of all that is known of the
Dawn-animal of the Laurentian rocks of Canada. This will include,
firstly: a descriptive notice of the Laurentian formation itself.
Secondly: a history of the steps which led to the discovery and proper
interpretation of this ancient fossil. Thirdly: the description of
Eozoon, and the explanation of the manner in which its remains have
been preserved. Fourthly: inquiries as to forms of animal life, its
contemporaries and immediate successors, or allied to it by zoological
affinity. Fifthly: the objections which have been urged against its
organic nature. And sixthly: the summing up of the lessons in science
which it is fitted to teach. On these points, while I shall endeavour
to state the substance of all that has been previously published, I
shall bring forward many new facts illustrative of points hitherto more
or less obscure, and shall endeavour so to picture these in themselves
and their relations, as to give distinct and vivid impressions to the
reader.
For the benefit of those who may not have access to the original
memoirs, or may not have time to consult them, I shall append to the
several chapters some of the technical details. These may be omitted by
the general reader; but will serve to make the work more complete and
useful as a book of reference.
The only preparation necessary for the unscientific reader of this
work, will be some little knowledge of the division of geological time
into successive ages, as represented by the diagram of formations
appended to this chapter, and more full explanations may be obtained by
consulting any of the numerous elementary manuals on geology, or "The
Story of the Earth and Man," by the writer of the present work.
TABULAR VIEW OF THE EARTH'S GEOLOGICAL HISTORY.
_Animal Kingdom._ _Geological Periods._ _Vegetable Kingdom._
Age of Man. CENOZOIC, OR Modern. Age of Angiosperms
NEOZOIC, OR Post-Pliocene, and Palms.
TERTIARY or Pleistocene.
Pliocene.
Miocene.
Age of Mammals. Eocene.
Age of Reptiles. MESOZOIC Cretaceous. Age of Cycads and
Jurassic. Pines.
Triassic.
Age of Amphibians PALÆOZOIC Permian. Age of Acrogens
and Fishes. Carboniferous. and Gymnosperms.
Erian, or Devonian.
Age of Mollusks, Upper Silurian.
Corals, and Lower Silurian, or
Crustaceans. Siluro-Cambrian.
Cambrian or
Primordial. Age of Algæ.
Age of Protozoa, EOZOIC Huronian. Beginning of Age
and dawn of Upper Laurentian. of Algæ.
Animal Life. Lower Laurentian.
[Illustration:
Plate II.
MAP SHEWING THE DISTRIBUTION OF THE LAURENTIAN LIMESTONES HOLDING EOZOON
IN THE COUNTIES OF OTTAWA & ARGENTEUIL.
_Drawn by M. R. Barlow_ _Stanford's Geog. Estab^t. Charing Cross, London._
Reprinted with additions from the Report of the Geology of Canada,
by Sir W. Logan, F.R.S., 1863.]