THE HISTORY OF A DISCOVERY.
It is a trite remark that most discoveries are made, not by one
person, but by the joint exertions of many, and that they have their
preparations made often long before they actually appear. In this
case the stable foundations were laid, years before the discovery
of Eozoon, by the careful surveys made by Sir William Logan and his
assistants, and the chemical examination of the rocks and minerals
by Dr. Sterry Hunt. On the other hand, Dr. Carpenter and others in
England were examining the structure of the shells of the humbler
inhabitants of the modern ocean, and the manner in which the pores of
their skeletons become infiltrated with mineral matter when deposited
in the sea-bottom. These laborious and apparently dissimilar branches
of scientific inquiry were destined to be united by a series of happy
discoveries, made not fortuitously but by painstaking and intelligent
observers. The discovery of the most ancient fossil was thus not the
chance picking up of a rare and curious specimen. It was not likely
to be found in this way; and if so found, it would have remained
unnoticed and of no scientific value, but for the accumulated stores of
zoological and palæontological knowledge, and the surveys previously
made, whereby the age and distribution of the Laurentian rocks and
the chemical conditions of their deposition and metamorphism were
ascertained.
[Illustration: Fig. 7. _Eozoon mineralized by Loganite and Dolomite._
(Collected by Dr. Wilson, of Perth.)]
The first specimens of Eozoon ever procured, in so far as known, were
collected at Burgess in Ontario by a veteran Canadian mineralogist,
Dr. Wilson of Perth, and were sent to Sir William Logan as mineral
specimens. Their chief interest at that time lay in the fact that
certain laminæ of a dark green mineral present in the specimens were
found, on analysis by Dr. Hunt, to be composed of a new hydrous
silicate, allied to serpentine, and which he named loganite: one of
these specimens is represented in fig. 7. The form of this mineral was
not suspected to be of organic origin. Some years after, in 1858, other
specimens, differently mineralized with the minerals serpentine and
pyroxene, were found by Mr. J. McMullen, an explorer in the service
of the Geological Survey, in the limestone of the Grand Calumet on
the River Ottawa. These seem to have at once struck Sir W. E. Logan
as resembling the Silurian fossils known as _Stromatopora_, and he
showed them to Mr. Billings, the palæontologist of the survey, and to
the writer, with this suggestion, confirming it with the sagacious
consideration that inasmuch as the Ottawa and Burgess specimens were
mineralized by different substances, yet were alike in form, there was
little probability that they were merely mineral or concretionary. Mr.
Billings was naturally unwilling to risk his reputation in affirming
the organic nature of such specimens; and my own suggestion was that
they should be sliced, and examined microscopically, and that if
fossils, as they presented merely concentric laminæ and no cells,
they would probably prove to be protozoa rather than corals. A few
slices were accordingly made, but no definite structure could be
detected. Nevertheless Sir William Logan took some of the specimens to
the meeting of the American Association at Springfield, in 1859, and
exhibited them as possibly Laurentian fossils; but the announcement was
evidently received with some incredulity. In 1862 they were exhibited
by Sir William to some geological friends in London, but he remarks
that "few seemed disposed to believe in their organic character, with
the exception of my friend Professor Ramsay." In 1863 the General
Report of the Geological Survey, summing up its work to that time,
was published, under the name of the _Geology of Canada_, and in this,
at page 49, will be found two figures of one of the Calumet specimens,
here reproduced, and which, though unaccompanied with any specific
name or technical description, were referred to as probably Laurentian
fossils. (Figs. 8 and 9.)
About this time Dr. Hunt happened to mention to me, in connection with
a paper on the mineralization of fossils which he was preparing, that
he proposed to notice the mode of preservation of certain fossil woods
and other things with which I was familiar, and that he would show me
the paper in proof, in order that he might have any suggestions that
occurred to me. On reading it, I observed, among other things, that
he alluded to the supposed Laurentian fossils, under the impression
that the organic part was represented by the serpentine or loganite,
and that the calcareous matter was the filling of the chambers. I took
exception to this, stating that though in the slices before examined
no structure was apparent, still my impression was that the calcareous
matter was the fossil, and the serpentine or loganite the filling. He
said--"In that case, would it not be well to re-examine the specimens,
and to try to discover which view is correct?" He mentioned at the same
time that Sir William had recently shown him some new and beautiful
specimens collected by Mr. Lowe, one of the explorers on the staff of
the Survey, from a third locality, at Grenville, on the Ottawa. It was
supposed that these might throw further light on the subject; and
accordingly Dr. Hunt suggested to Sir William to have additional slices
of these new specimens made by Mr. Weston, of the Survey, whose skill
as a preparer of these and other fossils has often done good service to
science. A few days thereafter, some slices were sent to me, and were
at once put under the microscope. I was delighted to find in one of the
first specimens examined a beautiful group of tubuli penetrating one of
the calcite layers. Here was evidence, not only that the calcite layers
represented the true skeleton of the fossil, but also of its affinities
with the Foraminifera, whose tubulated supplemental skeleton, as
described and figured by Dr. Carpenter, and represented in specimens
in my collection presented by him, was evidently of the same type with
that preserved in the canals of these ancient fossils. Fig. 10 is an
accurate representation of the first seen group of canals penetrated by
serpentine.
[Illustration: Fig. 8. _Weathered Specimen of Eozoon from the Calumet._
(Collected by Mr. McMullen.)]
[Illustration: Fig. 9. _Cross Section of the Specimen represented in
Fig. 8._
The dark parts are the laminæ of calcareous matter converging to the
outer surface.]
On showing the structures discovered to Sir William Logan, he entered
into the matter with enthusiasm, and had a great number of slices and
afterwards of decalcified specimens prepared, which were placed in my
hands for examination.
Feeling that the discovery was most important, but that it would be
met with determined scepticism by a great many geologists, I was
not content with examining the typical specimens of Eozoon, but had
slices prepared of every variety of Laurentian limestone, of altered
limestones from the Primordial and Silurian, and of serpentine
marbles of all the varieties furnished by our collections. These were
examined with ordinary and polarized light, and with every variety
of illumination. Dr. Hunt, on his part, undertook the chemical
investigation of the various associated minerals. An extensive series
of notes and camera tracings were made of all the appearances observed;
and of some of the more important structures beautiful drawings
were executed by the late Mr. H. S. Smith, the then palæontological
draughtsman of the Survey. The result of the whole investigation was a
firm conviction that the structure was organic and foraminiferal, and
that it could be distinguished from any merely mineral or crystalline
forms occurring in these or other limestones.
[Illustration: Fig. 10. _Group of Canals in the Supplemental Skeleton
of Eozoon._
Taken from the specimen in which they were first recognised.
Magnified.]
At this stage of the matter, and after exhibiting to Sir William all
the characteristic appearances in comparison with such concretionary,
dendritic, and crystalline structures as most resembled them, and also
with the structure of recent and fossil Foraminifera, I suggested that
the further prosecution of the matter should be handed over to Mr.
Billings, as palæontologist of the Survey, and as our highest authority
on the fossils of the older rocks. I was engaged in other researches,
and knew that no little labour must be devoted to the work and to its
publication, and that some controversy might be expected. Mr. Billings,
however, with his characteristic caution and modesty, declined. His
hands, he said, were full of other work, and he had not specially
studied the microscopic appearances of Foraminifera or of mineral
substances. It was finally arranged that I should prepare a description
of the fossil, which Sir William would take to London, along with Dr.
Hunt's notes, the more important specimens, and lists of the structures
observed in each. Sir William was to submit the manuscript and
specimens to Dr. Carpenter, or failing him to Prof. T. Rupert Jones, in
the hope that these eminent authorities would confirm our conclusions,
and bring forward new facts which I might have overlooked or been
ignorant of. Sir William saw both gentlemen, who gave their testimony
in favour of the organic and foraminiferal character of the specimens;
and Dr. Carpenter in particular gave much attention to the subject, and
worked out the structure of the primary cell-wall, which I had not
observed previously through a curious accident as to specimens.[J] Mr.
Lowe had been sent back to the Ottawa to explore, and just before Sir
William's departure had sent in some specimens from a new locality at
Petite Nation, similar in general appearance to those from Grenville,
which Sir William took with him unsliced to England. These showed in
a perfect manner the tubuli of the primary cell-wall, which I had in
vain tried to resolve in the Grenville specimens, and which I did
not see until after it had been detected by Dr. Carpenter in London.
Dr. Carpenter thus contributed in a very important manner to the
perfecting of the investigations begun in Canada, and on him has fallen
the greater part of their illustration and defence,[K] in so far as
Great Britain is concerned. Fig. 11, taken from one of Dr. Carpenter's
papers, shows the tubulated primitive wall as described by him.
[Footnote J: In papers by Dr. Carpenter, subsequently referred to.
Prof. Jones published an able exposition of the facts in the _Popular
Science Monthly_.]
[Footnote K: In _Quarterly Journal of Geological Society_, vol. xxii.;
_Proc. Royal Society_, vol. xv.; _Intellectual Observer_, 1865. _Annals
and Magazine of Natural History_, 1874; and other papers and notices.]
[Illustration: Fig. 11. _Portion of Eozoon magnified 100 diameters,
showing the original Cell-wall with Tubulation, and the Supplemental
Skeleton with Canals._ (_After Carpenter._)
(_a._) Original tubulated wall or "Nummuline layer," more magnified in
fig. 2. (_b, c._) "Intermediate skeleton," with canals.]
The immediate result was a composite paper in the _Proceedings of the
Geological Society_, by Sir W. E. Logan, Dr. Carpenter, Dr. Hunt, and
myself, in which the geology, palæontology, and mineralogy of _Eozoon
Canadense_ and its containing rocks were first given to the world.[L]
It cannot be wondered at that when geologists and palæontologists were
thus required to believe in the existence of organic remains in rocks
regarded as altogether Azoic and hopelessly barren of fossils, and
to carry back the dawn of life as far before those Primordial rocks,
which were supposed to contain its first traces, as these are before
the middle period of the earth's life history, some hesitation should
be felt. Further, the accurate appreciation of the evidence for such a
fossil as Eozoon required an amount of knowledge of minerals, of the
more humble types of animals, and of the conditions of mineralization
of organic remains, possessed by few even of professional geologists.
Thus Eozoon has met with some negative scepticism and a little positive
opposition,--though the latter has been small in amount, when we
consider the novel and startling character of the facts adduced.
[Footnote L: _Journal Geological Society_, February, 1865.]
"The united thickness," says Sir William Logan, "of these three great
series, the Lower and Upper Laurentian and Huronian, may possibly far
surpass that of all succeeding rocks, from the base of the Palæozoic
to the present time. We are thus carried back to a period so far
remote that the appearance of the so-called Primordial fauna may
be considered a comparatively modern event." So great a revolution
of thought, and this based on one fossil, of a character little
recognisable by geologists generally, might well tax the faith of a
class of men usually regarded as somewhat faithless and sceptical. Yet
this new extension of life has been generally received, and has found
its way into text-books and popular treatises. Its opponents have
been under the necessity of inventing the most strange and incredible
pseudomorphoses of mineral substances to account for the facts; and
evidently hold out rather in the spirit of adhesion to a lost cause
than with any hope of ultimate success. As might have been expected,
after the publication of the original paper, other facts developed
themselves. Mr. Vennor found other and scarcely altered specimens in
the Upper Laurentian or Huronian of Tudor. Gümbel recognised the
organism in Laurentian Rocks in Bavaria and elsewhere in Europe, and
discovered a new species in the Huronian of Bavaria.[M] Eozoon was
recognised in Laurentian limestones in Massachusetts[N] and New York,
and there has been a rapid growth of new facts increasing our knowledge
of Foraminifera of similar types in the succeeding Palæozoic rocks.
Special interest attaches to the discovery by Mr. Vennor of specimens
of Eozoon contained in a dark micaceous limestone at Tudor, in Ontario,
and really as little metamorphosed as many Silurian fossils. Though in
this state they show their minute structures less perfectly than in
the serpentine specimens, the fact is most important with reference
to the vindication of the animal nature of Eozoon. Another fact whose
significance is not to be over-estimated, is the recognition both by
Dr. Carpenter and myself of specimens in which the canals are occupied
by calcite like that of the organism itself. Quite recently I have, as
mentioned in the last chapter, been enabled to re-examine the locality
at Petite Nation originally discovered by Mr. Lowe, and am prepared to
show that all the facts with reference to the mode of occurrence of
the forms in the beds, and their association with layers of fragmental
Eozoon, are strictly in accordance with the theory that these old
Laurentian limestones are truly marine deposits, holding the remains of
the sea animals of their time.
[Footnote M: _Ueber das Vorkommen von Eozoon_, 1866.]
[Footnote N: By Mr. Bicknell at Newbury, and Mr. Burbank at Chelmsford.
The latter gentleman has since maintained that the limestones at the
latter place are not true beds; but his own descriptions and figures,
lead to the belief that this is an error of observation on his part.
The Eozoon in the Chelmsford specimens and in those of Warren, New
York, is in small and rare fragments in serpentinous limestone.]
Eozoon is not, however, the only witness to the great fact of
Laurentian life, of which it is the most conspicuous exponent. In many
of the Laurentian limestones, mixed with innumerable fragments of
Eozoon, there are other fragments with traces of organic structure of
a different character. There are also casts in silicious matter which
seem to indicate smaller species of Foraminifera. There are besides to
be summoned in evidence the enormous accumulations of carbon already
referred to as existing in the Laurentian rocks, and the worm-burrows,
of which very perfect traces exist in rocks probably of Upper Eozoic
age.
Other discoveries also are foreshadowed here. The microscope may
yet detect the true nature and affinities of some of the fragments
associated with Eozoon. Less altered portions of the Laurentian rocks
may be found, where even the vegetable matter may retain its organic
forms, and where fossils may be recognised by their external outlines
as well as by their internal structure. The Upper Laurentian and the
Huronian have yet to yield up their stores of life. Thus the time may
come when the rocks now called Primordial shall not be held to be so
in any strict sense, and when swarming dynasties of Protozoa and other
low forms of life may be known as inhabitants of oceans vastly ancient
as compared with even the old Primordial seas. Who knows whether even
the land of the Laurentian time may not have been clothed with plants,
perhaps as much more strange and weird than those of the Devonian and
Carboniferous, as those of the latter are when compared with modern
forests?
NOTES TO CHAPTER III.
(A.) Sir William E. Logan on the Discovery and Characters of Eozoon.
[_Journal of Geological Society_, February, 1865.]
"In the examination of these ancient rocks, the question has often
naturally occurred to me, whether during these remote periods, life
had yet appeared on the earth. The apparent absence of fossils from
the highly crystalline limestones did not seem to offer a proof in
the negative, any more than their undiscovered presence in newer
crystalline limestones where we have little doubt they have been
obliterated by metamorphic action; while the carbon which, in the
form of graphite, constitutes beds, or is disseminated through the
calcareous or siliceous strata of the Laurentian series, seems to be
an evidence of the existence of vegetation, since no one disputes the
organic character of this mineral in more recent rocks. My colleague,
Dr. T. Sterry Hunt, has argued for the existence of organic matters
at the earth's surface during the Laurentian period from the presence
of great beds of iron ore, and from the occurrence of metallic
sulphurets;[O] and finally, the evidence was strengthened by the
discovery of supposed organic forms. These were first brought to me,
in October, 1858, by Mr. J. McMullen, then attached as an explorer to
the Geological Survey of the province, from one of the limestones of
the Laurentian series occurring at the Grand Calumet, on the river
Ottawa.
[Footnote O: _Quarterly Journal of the Geological Society_, xv., 493.]
"Any organic remains which may have been entombed in these limestones
would, if they retained their calcareous character, be almost
certainly obliterated by crystallization; and it would only be by the
replacement of the original carbonate of lime by a different mineral
substance, or by an infiltration of such a substance into all the
pores and spaces in and about the fossil, that its form would be
preserved. The specimens from the Grand Calumet present parallel or
apparently concentric layers resembling those of Stromatopora, except
that they anastomose at various points. What were first considered
the layers are composed of crystallized pyroxene, while the then
supposed interstices consist of carbonate of lime. These specimens,
one of which is figured in _Geology of Canada_, p. 49, called to
memory others which had some years previously been obtained from Dr.
James Wilson, of Perth, and were then regarded merely as minerals.
They came, I believe, from masses in Burgess, but whether in place
is not quite certain; and they exhibit similar forms to those of the
Grand Calumet, composed of layers of a dark green magnesian silicate
(loganite); while what were taken for the interstices are filled with
crystalline dolomite. If the specimens from both these places were to
be regarded as the result of unaided mineral arrangement, it appeared
to me strange that identical forms should be derived from minerals
of such different composition. I was therefore disposed to look
upon them as fossils, and as such they were exhibited by me at the
meeting of the American Association for the Advancement of Science,
at Springfield, in August, 1859. See _Canadian Naturalist_, 1859,
iv., 300. In 1862 they were shown to some of my geological friends
in Great Britain; but no microscopic structure having been observed
belonging to them, few seemed disposed to believe in their organic
character, with the exception of my friend Professor Ramsay.
"One of the specimens had been sliced and submitted to microscopic
observation, but unfortunately it was one of those composed of
loganite and dolomite. In these, the minute structure is rarely
seen. The true character of the specimens thus remained in suspense
until last winter, when I accidentally observed indications of
similar forms in blocks of Laurentian limestone which had been
brought to our museum by Mr. James Lowe, one of our explorers, to
be sawn up for marble. In this case the forms were composed of
serpentine and calc-spar; and slices of them having been prepared
for the microscope, the minute structure was observed in the first
one submitted to inspection. At the request of Mr. Billings, the
palæontologist of our Survey, the specimens were confided for
examination and description to Dr. J. W. Dawson, of Montreal, our
most practised observer with the microscope; and the conclusions at
which he has arrived are appended to this communication. He finds
that the serpentine, which was supposed to replace the organic form,
really fills the interspaces of the calcareous fossil. This exhibits
in some parts a well-preserved organic structure, which Dr. Dawson
describes as that of a Foraminifer, growing in large sessile patches
after the manner of Polytrema and Carpenteria, but of much larger
dimensions, and presenting minute points which reveal a structure
resembling that of other Foraminiferal forms, as, for example
Calcarina and Nummulina.
"Dr. Dawson's description is accompanied by some remarks by Dr.
Sterry Hunt on the mineralogical relations of the fossil. He
observes that while the calcareous septa which form the skeleton of
the Foraminifer in general remain unchanged, the sarcode has been
replaced by certain silicates which have not only filled up the
chambers, cells, and septal orifices, but have been injected into
the minute tubuli, which are thus perfectly preserved, as may be
seen by removing the calcareous matter by an acid. The replacing
silicates are white pyroxene, serpentine, loganite, and pyrallolite
or rensselaerite. The pyroxene and serpentine are often found
in contact, filling contiguous chambers in the fossil, and were
evidently formed in consecutive stages of a continuous process. In
the Burgess specimens, while the sarcode is replaced by loganite, the
calcareous skeleton, as has already been stated, has been replaced
by dolomite, and the finer parts of the structure have been almost
wholly obliterated. But in the other specimens, where the skeleton
still preserves its calcareous character, the resemblance between
the mode of preservation of the ancient Laurentian Foraminifera, and
that of the allied forms in Tertiary and recent deposits (which,
as Ehrenberg, Bailey, and Pourtales have shown, are injected with
glauconite), is obvious.
"The Grenville specimens belong to the highest of the three already
mentioned zones of Laurentian limestone, and it has not yet been
ascertained whether the fossil extends to the two conformable lower
ones, or to the calcareous zones of the overlying unconformable
Upper Laurentian series. It has not yet either been determined
what relation the strata from which the Burgess and Grand Calumet
specimens have been obtained bear to the Grenville limestone or
to one another. The zone of Grenville limestone is in some places
about 1500 feet thick, and it appears to be divided for considerable
distances into two or three parts by very thick bands of gneiss.
One of these occupies a position towards the lower part of the
limestone, and may have a volume of between 100 and 200 feet. It is
at the base of the limestone that the fossil occurs. This part of
the zone is largely composed of great and small irregular masses of
white crystalline pyroxene, some of them twenty yards in length by
four or five wide. They appear to be confusedly placed one above
another, with many ragged interstices, and smoothly-worn, rounded,
large and small pits and sub-cylindrical cavities, some of them
pretty deep. The pyroxene, though it appears compact, presents a
multitude of small spaces consisting of carbonate of lime, and many
of these show minute structures similar to that of the fossil.
These masses of pyroxene may characterize a thickness of about 200
feet, and the interspaces among them are filled with a mixture of
serpentine and carbonate of lime. In general a sheet of pure dark
green serpentine invests each mass of pyroxene; the thickness of the
serpentine, varying from the sixteenth of an inch to several inches,
rarely exceeding half a foot. This is followed in different spots
by parallel, waving, irregularly alternating plates of carbonate of
lime and serpentine, which become gradually finer as they recede
from the pyroxene, and occasionally occupy a total thickness of
five or six inches. These portions constitute the unbroken fossil,
which may sometimes spread over an area of about a square foot, or
perhaps more. Other parts, immediately on the outside of the sheet of
serpentine, are occupied with about the same thickness of what appear
to be the ruins of the fossil, broken up into a more or less granular
mixture of calc-spar and serpentine, the former still showing minute
structure; and on the outside of the whole a similar mixture appears
to have been swept by currents and eddies into rudely parallel and
curving layers; the mixture becoming gradually more calcareous as it
recedes from the pyroxene. Sometimes beds of limestone of several
feet in thickness, with the green serpentine more or less aggregated
into layers, and studded with isolated lumps of pyroxene, are
irregularly interstratified in the mass of rock; and less frequently
there are met with lenticular patches of sandstone or granular
quartzite, of a foot in thickness and several yards in diameter,
holding in abundance small disseminated leaves of graphite.
"The general character of the rock connected with the fossil produces
the impression that it is a great Foraminiferal reef, in which the
pyroxenic masses represent a more ancient portion, which having
died, and having become much broken up and worn into cavities and
deep recesses, afforded a seat for a new growth of Foraminifera,
represented by the calcareo-serpentinous part. This in its turn
became broken up, leaving in some places uninjured portions of the
general form. The main difference between this Foraminiferal reef and
more recent coral-reefs seems to be that, while in the latter are
usually associated many shells and other organic remains, in the more
ancient one the only remains yet found are those of the animal which
built the reef."
(B.) NOTE BY SIR WILLIAM E. LOGAN, ON ADDITIONAL SPECIMENS OF EOZOON.
[_Journal of Geological Society_, August, 1867.]
"Since the subject of Laurentian fossils was placed before this
Society in the papers of Dr. Dawson, Dr. Carpenter, Dr. T. Sterry
Hunt, and myself, in 1865, additional specimens of Eozoon have been
obtained during the explorations of the Geological Survey of Canada.
These, as in the case of the specimens first discovered, have been
submitted to the examination of Dr. Dawson; and it will be observed,
from his remarks contained in the paper which is to follow, that one
of them has afforded further, and what appears to him conclusive,
evidence of their organic character. The specimens and remarks have
been submitted to Dr. Carpenter, who coincides with Dr. Dawson;
and the object of what I have to say in connection with these new
specimens is merely to point out the localities in which they have
been procured.
"The most important of these specimens was met with last summer by
Mr. G. H. Vennor, one of the assistants on the Canadian Geological
Survey, in the township of Tudor and county of Hastings, Ontario,
about forty-five miles inland from the north shore of Lake Ontario,
west of Kingston. It occurred on the surface of a layer, three inches
thick, of dark grey micaceous limestone or calc-schist, near the
middle of a great zone of similar rock, which is interstratified
with beds of yellowish-brown sandstone, gray close grained silicious
limestone, white coarsely granular limestone, and bands of dark
bluish compact limestone and black pyritiferous slates, to the whole
of which Mr. Vennor gives a thickness of 1000 feet. Beneath this zone
are gray and pink dolomites, bluish and grayish mica slates, with
conglomerates, diorites, and beds of magnetite, a red orthoclase
gneiss lying at the base. The whole series, according to Mr. Vennor's
section, which is appended, has a thickness of more than 12,000
feet; but the possible occurrence of more numerous folds than have
hitherto been detected, may hereafter render necessary a considerable
reduction.
"These measures appear to be arranged in the form of a trough,
to the eastward of which, and probably beneath them, there are
rocks resembling those of Grenville, from which the former differ
considerably in lithological character; it is therefore supposed
that the Hastings series may be somewhat higher in horizon than
that of Grenville. From the village of Madoc, the zone of gray
micaceous limestone, which has been particularly alluded to, runs
to the eastward on one side of the trough, in a nearly vertical
position into Elzivir, and on the other side to the northward,
through the township of Madoc into that of Tudor, partially and
unconformably overlaid in several places by horizontal beds of Lower
Silurian limestone, but gradually spreading, from a diminution of
the dip, from a breadth of half a mile to one of four miles. Where
it thus spreads out in Tudor it becomes suddenly interrupted for a
considerable part of its breadth by an isolated mass of anorthosite
rock, rising about 150 feet above the general plain, and supposed to
belong to the unconformable Upper Laurentian."
[Subsequent observations, however, render it probable that some of
the above beds may be Huronian.]
"The Tudor limestone is comparatively unaltered: and, in the specimen
obtained from it, the general form or skeleton of the fossil
(consisting of white carbonate of lime) is imbedded in the limestone,
without the presence of serpentine or other silicate, the colour of
the skeleton contrasting strongly with that of the rock. It does not
sink deep into the rock, the form having probably been loose and much
abraded on what is now the under part, before being entombed. On what
was the surface of the bed, the form presents a well-defined outline
on one side; in this and in the arrangement of the septal layers
it has a marked resemblance to the specimen first brought from the
Calumet, eighty miles to the north-east, and figured in the _Geology
of Canada_, p. 49; while all the forms from the Calumet, like that
from Tudor, are isolated, imbedded specimens, unconnected apparently
with any continuous reef, such as exists at Grenville and the Petite
Nation. It will be seen, from Dr. Dawson's paper, that the minute
structure is present in the Tudor specimen, though somewhat obscure;
but in respect to this, strong subsidiary evidence is derived from
fragments of Eozoon detected by Dr. Dawson in a specimen collected
by myself from the same zone of limestone near the village of Madoc,
in which the canal-system, much more distinctly displayed, is filled
with carbonate of lime, as quoted from Dr. Dawson by Dr. Carpenter
in the Journal of this Society for August, 1866.
"In Dr. Dawson's paper mention is made of specimens from Wentworth,
and others from Long Lake. In both of these localities the rock
yielding them belongs to the Grenville band, which is the uppermost
of the three great bands of limestone hitherto described as
interstratified in the Lower Laurentian series. That at Long Lake,
situated about twenty-five miles north of Côte St. Pierre in the
Petite Nation seigniory, where the best of the previous specimens
were obtained, is in the direct run of the limestone there: and like
it the Long Lake rock is of a serpentinous character. The locality
in Wentworth occurs on Lake Louisa, about sixteen miles north of
east from that of the first Grenville specimens, from which Côte St.
Pierre is about the same distance north of west, the lines measuring
these distances running across several important undulations in
the Grenville band in both directions. The Wentworth specimens are
imbedded in a portion of the Grenville band, which appears to have
escaped any great alteration, and is free from serpentine, though a
mixture of serpentine with white crystalline limestone occurs in the
band within a mile of the spot. From this grey limestone, which has
somewhat the aspect of a conglomerate, specimens have been obtained
resembling some of the figures given by Gümbel in his _Illustrations_
of the forms met with by him in the Laurentian rocks of Bavaria.
"In decalcifying by means of a dilute acid some of the specimens
from Côte St. Pierre, placed in his hands in 1864-65, Dr. Carpenter
found that the action of the acid was arrested at certain portions
of the skeleton, presenting a yellowish-brown surface; and he showed
me, two or three weeks ago, that in a specimen recently given him,
from the same locality, considerable portions of the general form
remained undissolved by such an acid. On partially reducing some
of these portions to a powder; however, we immediately observed
effervescence by the dilute acid; and strong acid produced it without
bruising. There is little doubt that these portions of the skeleton
are partially replaced by dolomite, as more recent fossils are
often known to be, of which there is a noted instance in the Trenton
limestone of Ottawa. But the circumstance is alluded to for the
purpose of comparing these dolomitized portions of the skeleton with
the specimens from Burgess, in which the replacement of the septal
layers by dolomite appears to be the general condition. In such of
these specimens as have been examined the minute structure seems to
be wholly, or almost wholly, destroyed; but it is probable that upon
a further investigation of the locality some spots will be found
to yield specimens in which the calcareous skeleton still exists
unreplaced by dolomite; and I may safely venture to predict that in
such specimens the minute structure, in respect both to canals and
tubuli, will be found as well preserved as in any of the specimens
from Côte St. Pierre.
"It was the general form on weathered surfaces, and its strong
resemblance to Stromatopora, which first attracted my attention to
Eozoon; and the persistence of it in two distinct minerals, pyroxene
and loganite, emboldened me, in 1857, to place before the Meeting of
the American Association for the Advancement of Science specimens of
it as probably a Laurentian fossil. After that, the form was found
preserved in a third mineral, serpentine; and in one of the previous
specimens it was then observed to pass continuously through two
of the minerals, pyroxene and serpentine. Now we have it imbedded
in limestone, just as most fossils are. In every case, with the
exception of the Burgess specimens, the general form is composed of
carbonate of lime; and we have good grounds for supposing it was
originally so in the Burgess specimens also. If, therefore, with such
evidence, and without the minute structure, I was, upon a calculation
of chances, disposed, in 1857, to look upon the form as organic, much
more must I so regard it when the chances have been so much augmented
by the subsequent accumulation of evidence of the same kind, and
the addition of the minute structure, as described by Dr. Dawson,
whose observations have been confirmed and added to by the highest
British authority upon the class of animals to which the form has
been referred, leaving in my mind no room whatever for doubt of its
organic character. Objections to it as an organism have been made by
Professors King and Rowney: but these appear to me to be based upon
the supposition that because some parts simulating organic structure
are undoubtedly mere mineral arrangement, therefore all parts are
mineral. Dr. Dawson has not proceeded upon the opposite supposition,
that because some parts are, in his opinion, undoubtedly organic,
therefore all parts simulating organic structure are organic; but
he has carefully distinguished between the mineral and organic
arrangements. I am aware, from having supplied him with a vast number
of specimens prepared for the microscope by the lapidary of the
Canadian Survey, from a series of rocks of Silurian and Huronian,
as well as Laurentian age, and from having followed the course of
his investigation as it proceeded, that nearly all the points of
objection of Messrs. King and Rowney passed in review before him
prior to his coming to the conclusions which he has published."
_Ascending Section of the Eozoic Rocks in the County of Hastings,
Ontario._ By Mr. H. G. Vennor.
Feet.
1. Reddish and flesh-coloured granitic gneiss, the thickness
of which is unknown; estimated at not less than 2,000
2. Grayish and flesh-coloured gneiss, sometimes hornblendic,
passing towards the summit into a dark mica-schist,
and including portions of greenish-white diorite;
mean of several pretty closely agreeing measurements, 10,400
3. Crystalline limestone, sometimes magnesian, including
lenticular patches of quartz, and broken and
contorted layers of quartzo-felspathic rock, rarely above
a few inches in thickness. This limestone, which includes
in Elzivir a one-foot bed of graphite, is sometimes
very thin, but in other places attains a thickness
of 750 feet; estimated as averaging 400
4. Hornblendic and dioritic rocks, massive or schistose,
occasionally associated near the base with dark
micaceous schists, and also with chloritic and epidotic
rocks, including beds of magnetite; average thickness 4,200
5. Crystalline and somewhat granular magnesian
limestone, occasionally interstratified with diorites, and
near the base with silicious slates and small beds of
impure steatite 330
This limestone, which is often silicious and ferruginous,
is metalliferous, holding disseminated copper
pyrites, blende, mispickel, and iron pyrites, the latter
also sometimes in beds of two or three feet. Gold occurs
in the limestone at the village of Madoc, associated with
an argentiferous gray copper ore, and in irregular veins
with bitter-spar, quartz, and a carbonaceous matter, at
the Richardson mine in Madoc.
6. Gray silicious or fined-grained mica-slates, with
an interstratified mass of about sixty feet of yellowish-white
dolomite divided into beds by thin layers of the
mica-slate, which, as well as the dolomite, often becomes
conglomerate, including rounded masses of gneiss and
quartzite from one to twelve inches in diameter 400
7. Bluish and grayish micaceous slate, interstratified
with layers of gneiss, and occasionally holding crystals
of magnetite. The whole division weathers to a rusty-brown 500
8. Gneissoid micaceous quartzites, banded gray and
white, with a few interstratified beds of silicious
limestone, and, like the last division, weathering rusty
brown 1,900
9. Gray micaceous limestone, sometimes plumbaginous,
becoming on its upper portion a calc-schist, but
more massive towards the base, where it is interstratified
with occasional layers of diorite, and layers of a
rusty-weathering gneiss like 8 1,100
This division in Tudor is traversed by numerous
N.W. and S.E. veins, holding galena in a gangue of
calcite and barytine. The Eozoon from Tudor here
described was obtained from about the middle of this
calcareous division, which appears to form the summit
of the Hastings series.
------
Total thickness 21,130
[Illustration:
PLATE IV.
_Magnified and Restored Section of a portion of Eozoon Canadense._
The portions in brown show the animal matter of the Chambers, Tubuli,
Canals, and Pseudopodia; the portions uncoloured, the calcareous skeleton.]
[Illustration: Fig. 12. _Amœba._ Fig. 13. _Actinophrys._
From original sketches.]