Further Discoveries of the Ichthyolite Beds.--Found in one
Locality under a Bed of Peat.--Discovered in another beneath
an ancient Burying-ground.--In a third underlying the Lias
Formation.--In a fourth overtopped by a still older Sandstone
Deposit.--Difficulties in ascertaining the true Place of a
newly-discovered Formation.--Caution against drawing too hasty
Inferences from the mere circumstance of Neighborhood.--The Writer
receives his first Assistance from without.--_Geological Appendix_
of the Messrs. Anderson, of Inverness.--Further Assistance from the
Researches of Agassiz.--Suggestions.--Dr. John Malcolmson.--His
Extensive Discoveries in Moray.--He submits to Agassiz a Drawing of
the _Pterichthys_.--Place of the Ichthyolites in the Scale at length
determined.--Two distinct Platforms of Being in the Formation to
which they belong.
I commenced forming a small collection, and set myself carefully to
examine the neighboring rocks for organisms of a similar character.
The eye becomes practised in such researches, and my labors were soon
repaid. Directly above the little bay there is a corn-field, and
beyond the field a wood of forest trees; and in this wood, in the
bottom of a water-course, scooped out of the rock through a bed of
peat, I found the stratified clay charged with scales. A few hundred
yards farther to the west there is a deep, wooded ravine cut through
a thick bed of red diluvial clay. The top of the bank directly
above is occupied by the ruins of an ancient chapel, and a group of
moss-grown tombstones; and in the gorge of this ravine, underlying
the little field of graves by about sixty feet, I discovered a still
more ancient place of sepulture--that of the ichthyolites. I explored
every bank, rock, and ravine on the northern or Cromarty Frith side
of the tongue of land, with its terminal point of granitic gneiss, to
which I have had such frequent occasion to refer, and then turned to
explore the southern, or Moray Frith side, in the rectilinear line
of the great valley. And here I was successful on a larger scale. A
range of lofty sandstone cliffs, hollowed by the sea, extends for
a distance of about two miles between two of the granitic knobs
or wedges of the line--the Southern Sutor and the hill of Eathie.
And along well nigh the entire length of this range of cliffs, I
succeeded in tracing a continuous ichthyolite bed, abounding in
remains, and lying far below the Lias, and unconformable to it. I
pursued my researches, and in the sides of a romantic precipitous
dell, through which the Burn of Eathie--a small, mossy stream--finds
its way to the Moray Frith, I again discovered the fish-beds running
deep into the interior of the country, with immense strata of a pale
yellow sandstone resting over them, and strata of a chocolate red
lying below. But their place in the geological scale was still to fix.
I had seen enough to convince me that they form a continuous convex
stratum in the sandstone spear-shaft, covering it saddle-wise
from side to side, dipping towards the Moray Frith on the south,
and to the Cromarty Frith on the north--that, as in a _bona
fide_ spear-shaft, the annual ring or layer of growth of one
season is overlaid by the annual rings of succeeding seasons, and
underlaid by those of preceding ones; so this huge semi-ring of
fossiliferous clays and limestones had its underlying semi-ring
of Red Sandstone, and its overlying semi-rings of yellow, of red,
and of gray sandstone. I knew, besides, that beneath there was a
semi-ring of conglomerate, the base of the system; and that, for
more than two hundred yards upwards, ring followed ring in unbroken
succession--now sandstone, now limestone, now stratified clay. But
though intimately acquainted with these lower rocks for more than a
hundred fathoms from their base upwards, and with the upper rocks
on both sides the ichthyolitic bed for more than a hundred feet,
there was an intervening hiatus, whose extent at this period I found
it impossible to ascertain. And hence my uncertainty regarding the
place of the ichthyolites, seeing that whole formations might be
represented by the occurring gap. On the Moray Frith side, where
the sections are of huge extent, a doubtful repeat in the strata at
one point of junction, and an abrupt fault at another, cuts off the
upper series of beds to which the organisms belong, from the lower
to which the great conglomerate belongs. On the Cromarty Frith side
the sections are mere detached patches, obscured at every point by
diluvium and soil; and, in conceiving of the whole as a continuous
line, with the Lias a-top and the granite group at the bottom, I was
ever reminded of those coast-lines of the ancient geographers, where
a few uncertain dots, a few deeper markings, and here and there a
blank space or two, showed the blended results of conjecture and
discovery--whether they give a _Terra Incognita Australia_ to the one
hemisphere, or a North-Western passage to the other. The ichthyolites
in a section so doubtful might be regarded as belonging to either
the Old or the New Red Sandstone--to the Coal Measures, or to the
Mountain Limestone. All was uncertainty.
One remark in the passing: it may teach the young geologist to be
cautious in his inferences, and illustrate, besides, those gaps
which occur in the geological scale. I had now discovered the
ichthyolite beds in five different localities; in one of these--the
first discovered--there is no overlying stratum; it seems as if
the bed formed the top of the formation: in all the others the
overlying stratum is different, and belongs to distant and widely
separated ages. We cut in one locality through a peat moss--part of
the ruins, perhaps, of one of those forests which covered, about the
commencement of the Christian era, well nigh the entire surface of
the island, and sheltered the naked inhabitants from the legions of
Agricola. We find, as we dig, huge trunks of oak and elm, cones of
the Scotch fir, handfuls of hazel-nuts, and bones and horns of the
roe and the red deer. The writer, when a boy, found among the peat
the horn of a gigantic elk. And, forming the bottom of this recent
deposit, and _lying conformably to it_, we find the ichthyolite
beds, with their antique organisms. The remains of oak and elm
leaves, and of the spikes and cones of the pine, lie within half
a foot of the remains of the _Coccosteus_ and _Diplopterus_. We
dig in another locality through an ancient burying-ground; we pass
through a superior stratum of skulls and coffins, and an inferior
stratum, barren in organic remains, and then arrive at the stratified
clays, with their ichthyolites. In a third locality we find these in
junction with the Lias, and underlying its lignites, ammonites, and
belemnites, just as we see them underlying, in the other two, the
human bones and the peat moss. And in yet a fourth locality we see
them overlaid by immense arenaceous beds, that belong evidently, as
their mineralogical character testifies, to either the Old or the
New Red Sandstone. The convulsions and revolutions of the geological
world, like those of the political, are sad confounders of place
and station, and bring into close fellowship the high and the low;
nor is it safe in either world,--such have been the effects of the
disturbing agencies,--to judge of ancient relations by existing
neighborhoods, or of original situations by present places of
occupancy. "Misery," says Shakspeare, "makes strange bedfellows."
The changes and convulsions of the geological world have made strange
bedfellows too. I have seen fossils of the Upper Lias and of the
Lower Old Red Sandstone washed together by the same wave, out of
what might be taken, on a cursory survey, for the same bed, and then
mingled with recent shells, algæ, branches of trees, and fragments of
wrecks on the same sea-beach.
Years passed, and in 1834 I received my first assistance from
without, through the kindness of the Messrs. Anderson, of Inverness,
who this year published their Guide to the _Highlands and Islands
of Scotland_--a work which has never received half its due measure
of praise. It contains, in a condensed and very pleasing form, the
accumulated gleanings, for half a lifetime, of two very superior
men, skilled in science, and of highly cultivated taste and literary
ability; whose remarks, from their intimate acquaintance with every
foot-breadth of country which they describe, invariably exhibit
that freshness of actual observation, recorded on the spot, which
Gray regarded as "worth whole cart-loads of recollection." But
what chiefly interested me in their work was its dissertative
appendices--admirable digests of the Natural History, Antiquities,
and Geology of the country. The appendix devoted to Geology,
consisting of fifty closely printed pages,--abridged in part from the
highest geological authorities, and in much greater part the result
of original observation,--contains, beyond comparison, the completest
description of the rocks, fossils, and formations of the Northern
and Western Highlands, which has yet been given to the public in a
popular form. I perused it with intense interest, and learned from
it, for the first time, of the fossil fishes of Caithness and Gamrie.
There was almost nothing known, at the period, of the oryctology of
the older rocks--little, indeed, of that of the Old Red Sandstone,
in its proper character as such; and with no such guiding clew
as has since been furnished by Agassiz, and the later researches
of Mr. Murchison, the writer of the appendix had recorded as his
ultimate conclusion, that "the middle schistoze system of Caithness,
containing the fossil fish, was intermediate in geological character
and position between the Old and New Red Sandstone formations." The
ichthyolites of Gamrie he described as resembling those of Caithness;
and I at once recognized, in his minute descriptions of both, the
fossil fish of Cromarty. The mineralogical accompaniments, too,
seemed nearly the same. In Caithness, the animal remains are mixed
up in some places with a black bituminous matter like tar. I had but
lately found among the beds of the little bay a mass of soft adhesive
bitumen, hermetically sealed up in the limestone, which, when broken
open, reminded me, from the powerful odor it cast, and which filled
for several days the room in which I kept it, of the old Gaulish
mummy of which we find so minute account in the Natural History of
Goldsmith. The nodules which enclosed the organisms at Gamrie were
described as of a sub-crystalline, radiating, fibrous structure. So
much was this the case with some of the nodules at Cromarty, that
they had often reminded me, when freshly broken, though composed of
pure carbonate of lime, of masses of asbestos. The scales and bones
of the Caithness ichthyolites were blended, it was stated, with the
fragments of a "supposed tortoise nearly allied to trionyx;" one of
the ichthyolites, a _Dipterus_, was characterized by large scales,
a double dorsal, and a one-sided tail; the entire lack of shells
and zoöphytes was remarked, and the abundance of obscure vegetable
impressions. In short, had the accomplished writer of the appendix
been briefly describing the beds at Cromarty, instead of those of
Caithness and Gamrie, he might have employed the same terms, and
remarked the same circumstances--the striated nodules, the mineral
tar, the vegetable impressions, the absence of shells and zoöphytes,
the large-scaled, and double-finned ichthyolites--the peculiarities
of which applied equally to the _Dipterus_ and _Diplopterus_--and
the supposed tortoise, in which I once recognized the _Coccosteus_.
It was much to know, that this doubtful formation--for as doubtful
I still regarded it--was of such considerable extent, and occurred
in localities so widely separated. I corresponded with the courteous
author of the appendix, at that time General Secretary to the
Northern Institution for the Promotion of Science and Literature,
and Conservator of its Museum; and, forwarding to him duplicates of
some of my better specimens, had, as I had anticipated, the generic
identity of the Cromarty ichthyolites with those of Caithness and
Gamrie fully confirmed.
My narrative is, I am afraid, becoming tedious; but it embodies
somewhat more than the mere history of a sort of Robinson Crusoe in
Geology, cut off for years from all intercourse with his kind. It
contains, also, the history of a formation in its connection with
science; and the reader will, I trust, bear with me for a few pages
more. Seasons passed; and I received new light from the researches
of Agassiz, which, if it did not show me my way more clearly,
rendered it at least more interesting, by associating with it one
of those wonderful truths, stranger that fictions, which rise ever
and anon from the profounder depths of science, and whose use, in
their connection with the human intellect, seems to be to stimulate
the faculties. I have often had occasion to refer to the one-sided
condition of tail characteristic of the ichthyolites of the Old Red
Sandstone. It characterizes, says Agassiz, the fish of all the more
ancient formations. At one certain point in the descending scale
Nature entirely alters her plan in the formation of the tail. All
the ichthyolites above are fashioned after one particular type--all
below after another and different type. The bibliographer can tell
at what periods in the history of letters one character ceased to
be employed and another came into use. Black letter, for instance,
in our own country, was scarce ever resorted to for purposes of
general literature after the reign of James VI.; and in manuscript
writing the Italian hand superseded the Saxon about the close of
the seventeenth century. Now, is it not truly wonderful to find an
analogous change of character in that pictorial history of the past
which Geology furnishes? From the first appearance of vertebrated
existences to the middle beds of the New Red Sandstone,--a space
including the Upper Ludlow rocks, the Old Red Sandstone in all
its members, the Mountain Limestone, with the Limestone of Burdie
House, the Coal Measures, the Lower New Red, and the Magnesian
Limestone,--we find only the ancient or unequally lobed type of
tail. In all the formations above, including the Lias, the Oolite,
Middle, Upper, and Lower, the Wealden, the Green-Sand, the Chalk,
and the Tertiary, we find only the equally-lobed condition of tail.
And it is more than probable, that, with the tail, the character of
the skeleton also changed; that the more ancient type characterized,
throughout, the semi-cartilaginous order of fishes, just as the more
modern type characterizes the osseous fishes; and that the upper line
of the Magnesian Limestone marks the period at which the order became
extinct. Conjecture lacks footing in grappling with a revolution
so extensive and so wonderful. Shall I venture to throw out a
suggestion on the subject, in connection with another suggestion
which has emanated from one of the first of living geologists? Fish,
of all existing creatures, seem the most capable of sustaining high
degrees of heat, and are to be found in some of the hot springs of
Continental Europe, where it is supposed scarce any other animal
could live. Now, all the fish of the ancient type are thickly covered
by a defensive armor of bone, arranged in plates, bars, or scales,
or all the three modes together, as in the _Osteolepis_ and one
half its contemporaries. The one-sided tail is united invariably
to a strong cuirass. And it has been suggested by Dr. Buckland,
that this strong cuirass may have formed a sort of defence against
the injurious effects of a highly heated surrounding medium. The
suggestion is, of course, based purely on hypothesis. It may be
stated, in direct connection with it, however, that in the Lias--the
first richly fossiliferous formation overlying that in which the
change occurred--we find, for the first time in the geological
system, decided indications of a change of seasons. The foot-prints
of winter are left impressed amid the lignites of the Cromarty Lias.
In a specimen now before me, the alternations of summer heat and
winter cold are as distinctly marked in the annual rings as in the
pines or larches of our present forests; whereas in the earlier
lignites, contemporary with ichthyolites of the ancient type, either
no annual rings appear, or the markings, if present, are both faint
and unfrequent. _Just ere winter began to take its place among
the seasons, the fish fitted for living in a highly heated medium
disappeared:_ they were created to inhabit a thermal ocean, and died
away as it cooled down. Fish of a similar type may now inhabit the
seas of Venus, or even of Jupiter, which, from its enormous bulk,
though greatly more distant from the sun than our earth, may still
powerfully retain the internal heat.
I still pursued my inquiries, and received a valuable auxiliary in a
gentleman from India, Dr. John Malcolmson, of Madras--a member of the
London Geological Society, and a man of high scientific attainments
and great general knowledge. Above all, I found him to possess, in
a remarkable degree, that spirit of research, almost amounting to a
passion, which invariably marks the superior man. He had spent month
after month under the burning sun of India, amid fever marshes and
tiger jungles, acquainting himself with the unexplored geological
field which, only a few years ago, that vast continent presented,
and in collecting fossils hitherto unnamed and undescribed. He had
pursued his inquiries, too, along the coasts of the Red Sea, and far
upwards on the banks of the Nile; and now, in returning for a time
to his own country, he had brought with him the determination of
knowing it thoroughly as a man of science and a geologist. I had the
pleasure of first introducing him to the ichthyolites of the Lower
Old Red Sandstone, by bringing him to my first-discovered bed, and
laying open, by a blow of the hammer, a beautiful _Osteolepis_. He
was much interested in the fossils of my little collection, and at
once decided that the formation which contained them could be no
representative of the Coal Measures. After ranging over the various
beds on both sides the rectilinear ridge, and acquainting himself
thoroughly with their organisms, he set out to explore the Lower Old
Red Sandstones of Moray and Banff, hitherto deemed peculiarly barren,
but whose character too much resembled that of the rocks which he had
now ascertained to be so abundant in fossils, not to be held worthy
of further examination. He explored the banks of the Spey, and found
the ichthyolite beds extensively developed at Dipple, in the middle
of an Old Red Sandstone district. He pursued his researches, and
traced the formation in ravines and the beds of rivers, from the
village of Buckie to near the field of Culloden; he found it exposed
in the banks of the Nairn, in the ravines above Cawdor Castle, on the
eastern side of the hill of Rait, at Clune, Lethen-bar, and in the
vale of Rothes--and in every instance low in the Old Reel Sandstone.
The formation hitherto deemed so barren in remains proved one of
the richest of them all, if not in tribes and families, at least in
individual fossils; and the reader may form some idea of the extent
in which it has already been proved fossiliferous, when he remembers
that the tract includes as its extremes Orkney, Gamrie, and the
north-eastern gorge of the great Caledonian Valley. The ichthyolites
were discovered in the latter locality in the quarry of Inches, three
miles beyond Inverness, by Mr. George Anderson, the gentleman to
whose geological attainments, as one of the authors of the _Guide
Book_, I have lately had occasion to refer.
I had now corresponded for several years with a little circle of
geological friends, and had described in my letters, and in some
instances had attempted to figure in them, my newly-found fossils.
A letter which I wrote early in 1838 to Dr. Malcolmson, then at
Paris, and which contained a rude drawing of the _Pterichthys_,
was submitted to Agassiz, and the curiosity of the naturalist was
excited. He examined the figure, rather, however, with interest
than surprise, and read the accompanying description, not in the
least inclined to scepticism by the singularity of its details. He
had looked on too many wonders of a similar cast to believe that
he had exhausted them, or to evince any astonishment that Geology
should be found to contain one wonder more. Some months after, I
sent a restored drawing of the same fossil to the Elgin Scientific
Society. I must state, however, that the restoration was by no
means complete. The paddle-like arms were placed further below
the shoulders than in any actual species; and I had transferred,
by mistake, to the creature's upper side, some of the plates of
the _Coccosteus_. Still the type was unequivocally that of the
_Pterichthys_. The secretary of the Society, Mr. Patrick Duff, an
excellent geologist, to whose labors, in an upper formation of
the Old Red Sandstone, I shall have afterwards occasion to refer,
questioned, as he well might, some of the details of the figure,
and we corresponded for several weeks regarding it, somewhat
in the style of Jonathan Oldbuck and his antiquarian friend,
who succeeded in settling the meaning of two whole words, in an
antique inscription, in little more than two years. Most of the
other members looked upon the entire drawing, so strange did the
appearance seem, as embodying a fiction of the same class with
those embodied in the pictured griffins and unicorns of mythologic
Zoölogy; and, in amusing themselves with it, they bestowed on its
betailed and bepaddled figure, as if in anticipation of Agassiz,
the name of the draughtsman. Not many months after, however, a
_bona fide_ _Pterichthys_ turned up in one of the newly discovered
beds of Nairnshire, and the Association ceased to joke, and began
to wonder. T merely mention the circumstance in connection with a
right challenged, at the late meeting of the British Association at
Glasgow, by a gentleman of Elgin, to be regarded as the original
discoverer of the _Pterichthys_. I am, of course, far from supposing
that the discovery was not actually made, but regret that it should
have been kept so close a secret at a time when it might have stood
the other discoverer of the creature in such stead.
The exact place of the ichthyolites in the system was still to fix.
I was spending a day, early in the winter of 1839, among the nearly
vertical strata that lean against the Northern Sutor. The section
there presented is washed by the tide for nearly three hundred yards
from where it rests on the granitic gneiss; and each succeeding
stratum in the ascending order may be as clearly traced as the
alternate white and black squares in a marble pavement. First there
is a bed of conglomerate two hundred and fifteen feet in thickness,
"identical in structure," say Professor Sedgwick and Mr. Murchison,
u with the older red conglomerates of Cumberland and the Island of
Arran,[AJ] and which cannot be distinguished from those conglomerates
which lean against the southern flank of the Grampians, and on which
Dunnottar Castle is built. Immediately above the conglomerate there
is a hundred and fourteen feet more of coarse sandstone strata, of
a reddish yellow hue, with occasionally a few pebbles enclosed, and
then twenty-seven feet additional of limestone and stratified clay.
There are no breaks, no faults, no thinning out of strata--all the
beds lie parallel, showing regular deposition. I had passed over
the section twenty times before, and had carefully examined the
limestone and the clay, but in vain. On this occasion, however, I was
more fortunate. I struck off a fragment. It contained a vegetable
impression of the same character with those of the ichthyolite beds;
and after an hour's diligent search, I had turned out from the
heart of the stratum plates and scales enough to fill a shelf in a
museum--the helmet-like snout of an Osteolepis, the thorn-like spine
of a _Cheiracanthus_, and a _Coccosteus_ well nigh entire. I had at
length, after a search of nearly ten years, found the true place of
the ichthyolite bed. The reader may smile, but I hope the smile will
be a good-natured one; a simple pleasure may be not the less sincere
on account of its simplicity; and "little things are great to little
men." I passed over and over the strata, and found there could be no
mistake. The place of the fossil fish in the scale is little more
than a hundred feet above the top, and not much more than a hundred
yards above the base of the great conglomerate; and there lie over it
in this section about five hundred feet of soft, arenaceous stone,
with here and there alternating bands of limestone and beds of clay
studded with nodules--all belonging to the inferior Old Red Sandstone.
[Footnote AJ: Different in one respect from the conglomerates of
Arran. It abounds in rolled fragments of granite, whereas in those
of Arran there occur no pebbles of this rock. Arran has now its
granite in abundance; the northern locality has none; though, when
the conglomerates of the Lower Old Red Sandstone were in the course
of forming, the case was exactly the reverse.]
The enormous depth of the Old Red Sandstone of England has been
divided by Mr. Murchison into three members, or formations--the
division adopted in his _Elements_ by Mr. Lyell, as quoted in an
early chapter. These are, the lowest, or Tilestone formation, the
middle, or Cornstone formation, and the uppermost, or Quartzose
conglomerate formation. The terms are derived from mineralogical
characters, and inadequate as designations, therefore, like that of
the Old Red Sandstone itself, which, in many of its deposits, is
not _sandstone_, and is not _red_. But they serve to express great
natural divisions. Now the Tilestone member of England represents,
as I have already stated, this Lower Old Red Sandstone formation of
Scotland; but its extent of vertical development, compared with that
of the other two members of the system, is strikingly different in
the two countries. The Tilestones compose the least of the three
divisions in England; their representative in Scotland forms by much
the greatest of the three; and there seems to be zoölogical as well
as lithological evidence that its formation must have occupied no
brief period. _The same genera occur in its upper as in its lower
beds, but the species appear to be different._ I shall briefly state
the evidence of this very curious fact.
The seat of Sir William Gordon Camming, of Altyre, is in the
neighborhood of one of the Morayshire deposits discovered by Mr.
Malcolmson; and for the greater part of the last two years Lady
Gordon Gumming has been engaged in making a collection of its
peculiar fossils, which already fills an entire apartment. The object
of her Ladyship was the illustration of the Geology of the district,
and all she sought in it on her own behalf was congenial employment
for a singularly elegant and comprehensive mind. But her labors have
rendered her a benefactor to science. Her collection was visited,
shortly after the late meeting of the British Association in Glasgow,
by Agassiz and Dr. Buckland; and great was the surprise and delight
of the philosophers to find that the whole was new to Geology. All
the species, amounting to eleven, and at least one of the genera,
that of the _Glyptolepis_, were different from any Agassiz had ever
seen or described before. The deposit so successfully explored by
her Ladyship occurs high in the lower formation. Agassiz, shortly
after, in comparing the collection of Dr. Traill (a collection
formed at Orkney) with that of the writer, (a collection made at
Cromarty,) was struck by the specific identity of the specimens. In
the instances in which the genera agreed, he found that the species
agreed also, though the ichthyolites of both differed specifically
from the ichthyolites of Caithness, which occur chiefly in the upper
beds of the formation, and from those also of Lady Cumming of Altyre,
which occur, as I have said, at the top. And in examining into the
cause, it was found that the two collections, though furnished by
localities more than a hundred miles apart, were yet derived, if
I may so express myself, from the same low platform, both alike
representing the fossiliferous base of the system, and both removed
but by a single stage from the great unfossiliferous conglomerate
below. Thus there seem to be what may be termed two stories of
being in this lower formation--stories in which the groups, though
generically identical, are specifically dissimilar.[AK]
[Footnote AK: Since this period, however, several species identical
with those of Cromarty have been found in the Morayshire deposits.]