PERIOD--CONTINUED.
Delta and Alluvial Plain of the Nile.
Burnt Bricks in Egypt before the Roman Era.
Borings in 1851-54.
Ancient Mounds of the Valley of the Ohio.
Their Antiquity.
Sepulchral Mound at Santos in Brazil.
Delta of the Mississippi.
Ancient Human Remains in Coral Reefs of Florida.
Changes in Physical Geography in the Human Period.
Buried Canoes in Marine Strata near Glasgow.
Upheaval since the Roman Occupation of the Shores of the Firth of Forth.
Fossil Whales near Stirling.
Upraised Marine Strata of Sweden on Shores of the Baltic and the Ocean.
Attempts to compute their Age.
DELTA AND ALLUVIAL PLAIN OF THE NILE.
Some new facts of high interest illustrating the geology of the alluvial
land of Egypt were brought to light between the years 1851 and 1854,
in consequence of investigations suggested to the Royal Society by Mr.
Leonard Horner, and which were partly carried out at the expense of
the Society. The practical part of the undertaking was entrusted by Mr.
Horner to an Armenian officer of engineers, Hekekyan Bey, who had for
many years pursued his scientific studies in England, and was in every
way highly qualified for the task.
It was soon found that to obtain the required information respecting
the nature, depth, and contents of the Nile mud in various parts of
the valley, a larger outlay was called for than had been originally
contemplated. This expense the late viceroy, Abbas Pasha, munificently
undertook to defray out of his treasury, and his successor, after his
death, continued the operations with the same princely liberality.
Several engineers and a body of sixty workmen were employed under the
superintendence of Hekekyan Bey, men inured to the climate and able to
carry on the sinking of shafts and borings during the hot months, after
the waters of the Nile had subsided, and in a season which would have
been fatal to Europeans.
The results of chief importance arising out of this inquiry were
obtained from two sets of shafts and borings sunk at intervals in lines
crossing the great valley from east to west. One of these consisted of
no fewer than fifty-one pits and artesian borings, made where the
valley is 16 miles wide from side to side between the Arabian and Libyan
deserts, in the latitude of Heliopolis, about 8 miles above the apex of
the delta. The other line of borings and pits, twenty-seven in number,
was in the parallel of Memphis, where the valley is only five miles
broad.
Everywhere in these sections the sediment passed through was similar in
composition to the ordinary Nile mud of the present day, except near the
margin of the valley, where thin layers of quartzose sand, such as is
sometimes blown from the adjacent desert by violent winds, were observed
to alternate with the loam.
A remarkable absence of lamination and stratification was observed
almost universally in the sediment brought up from all points except
where the sandy layers above alluded to occurred. Mr. Horner attributes
this want of all indication of successive deposition to the extreme
thinness of the film of matter which is thrown down annually on the
great alluvial plain during the season of inundation. The tenuity of
this layer must indeed be extreme, if the French engineers are tolerably
correct in their estimate of the amount of sediment formed in a century,
which they suppose not to exceed on the average 5 inches. When the
waters subside, this thin layer of new soil, exposed to a hot sun, dries
rapidly, and clouds of dust are raised by the winds. The superficial
deposit, moreover, is disturbed almost everywhere by agricultural
labours, and even were this not the case, the action of worms, insects,
and the roots of plants would suffice to confound together the deposits
of two successive years.
All the remains of organic bodies, such as land-shells, and the bones
of quadrupeds, found during the excavations belonged to living species.
Bones of the ox, hog, dog, dromedary and ass were not uncommon, but no
vestiges of extinct mammalia. No marine shells were anywhere detected;
but this was to be expected, as the borings, though they sometimes
reached as low as the level of the Mediterranean, were never carried
down below it--a circumstance much to be regretted, since where artesian
borings have been made in deltas, as in those of the Po and Ganges, to
the depth of several hundred feet below the sea level it has been
found, contrary to expectation, that the deposits passed through were
fluviatile throughout, implying, probably, that a general subsidence of
those deltas and alluvial formations has taken place. Whether there has
been in like manner a sinking of the land in Egypt, we have as yet no
means of proving; but Sir Gardner Wilkinson infers it from the position
in the delta on the shore near Alexandria of the tombs commonly called
Cleopatra's Baths, which cannot, he says, have been originally built so
as to be exposed to the sea which now fills them, but must have stood on
land above the level of the Mediterranean. The same author adduces, as
additional signs of subsidence, some ruined towns, now half under water,
in the Lake Menzaleh, and channels of ancient arms of the Nile submerged
with their banks beneath the waters of that same lagoon.
In some instances, the excavations made under the superintendence of
Hekekyan Bey were on a large scale for the first 16 or 24 feet, in which
cases jars, vases, pots and a small human figure in burnt clay, a copper
knife, and other entire articles were dug up; but when water soaking
through from the Nile was reached the boring instrument used was too
small to allow of more than fragments of works of art being brought up.
Pieces of burnt brick and pottery were extracted almost everywhere, and
from all depths, even where they sank 60 feet below the surface towards
the central parts of the valley. In none of these cases did they get
to the bottom of the alluvial soil. It has been objected, among other
criticisms, that the Arabs can always find whatever their employers
desire to obtain. Even those who are too well acquainted with the
sagacity and energy of Hekekyan Bey to suspect him of having been
deceived, have suggested that the artificial objects might have fallen
into old wells which had been filled up. This notion is inadmissible
for many reasons. Of the ninety-five shafts and borings, seventy or more
were made far from the sites of towns or villages; and allowing that
every field may once have had its well, there would be but small chance
of the borings striking upon the site even of a small number of them in
seventy experiments.
Others have suggested that the Nile may have wandered over the whole
valley, undermining its banks on one side and filling up old channels
on the other. It has also been asked whether the delta with the numerous
shifting arms of the river may not once have been at every point where
the auger pierced.*
(* For a detailed account of these sections, see Mr.
Horner's paper in the "Philosophical Transactions" for 1855
to 1858.)
To all these objections there are two obvious answers:--First, in
historical times the Nile has on the whole been very stationary, and
has not shifted its position in the valley; secondly, if the mud pierced
through had been thrown down by the river in ancient channels, it would
have been stratified, and would not have corresponded so closely with
inundation mud, we learn from Captain Newbold that he observed in some
excavations in the great plain alternations of sand and clay, such as
are seen in the modern banks of the Nile; but in the borings made by
Hekekyan Bey, such stratification seems scarcely in any case to have
been detected.
The great aim of the criticisms above enumerated has been to get rid of
the supposed anomaly of finding burnt brick and pottery at depths and
places which would give them claim to an antiquity far exceeding that of
the Roman domination in Egypt. For until the time of the Romans, it is
said, no clay was burnt into bricks in the valley of the Nile. But a
distinguished antiquary, Mr. S. Birch, assures me that this notion is
altogether erroneous, and that he has under his charge in the British
Museum, first, a small rectangular baked brick, which came from a Theban
tomb which bears the name of Thothmes, a superintendent of the granaries
of the god Amen Ra, the style of art, inscription, and name, showing
that it is as old as the 18th dynasty (about 1450 B.C.); secondly, a
brick bearing an inscription, partly obliterated, but ending with the
words "of the temple of Amen Ra." This brick, decidedly long anterior to
the Roman dominion, is referred conjecturally, by Mr. Birch, to the 19th
dynasty, or 1300 B.C. Sir Gardner Wilkinson has also in his possession
pieces of mortar, which he took from each of the three great pyramids,
in which bits of broken pottery and of burnt clay or brick are embedded.
M. Girard, of the French expedition to Egypt, supposed the average rate
of the increase of Nile mud on the plain between Assouan and Cairo to
be five English inches in a century. This conclusion, according to Mr.
Horner, is very vague, and founded on insufficient data; the amount of
matter thrown down by the waters in different parts of the plain varying
so much that to strike an average with any approach to accuracy must
be most difficult. Were we to assume six inches in a century, the burnt
brick met with at a depth of 60 feet would be 12,000 years old.
Another fragment of red brick was found by Linant Bey, in a boring 72
feet deep, being 2 or 3 feet below the level of the Mediterranean,
in the parallel of the apex of the delta, 200 metres distant from the
river, on the Libyan side of the Rosetta branch.*
(* Horner "Philosophical Transactions" 1858.)
M. Rosiere, in the great French work on Egypt, has estimated the mean
rate of deposit of sediment in the delta at 2 1/4 inches in a century;*
were we to take 2 1/2 inches, a work of art 72 feet deep must have been
buried more than 30,000 years ago.
(* Description de l'Egypte "Histoire Naturelle" tome 2 page
494.)
But if the boring of Linant Bey was made where an arm of the river had
been silted up at a time when the apex of the delta was somewhat farther
south, or more distant from the sea than now, the brick in question
might be comparatively very modern.
The experiments instituted by Mr. Horner at the pedestal of the fallen
statue of King Rameses at Memphis, in the hope of obtaining an accurate
chronometric scale for testing the age of a given thickness of
Nile sediment, are held by some experienced Egyptologists not to be
satisfactory, on the ground of the uncertainty of the rate of deposit
accumulated at that locality. The point sought to be determined was the
exact amount of Nile mud which had accumulated there since the time when
that statue is supposed by some antiquaries to have been erected. Could
we have obtained possession of such a measure, the rate of deposition
might be judged of, approximately at least, whenever similar mud
was observed in other places, or below the foundations of those same
monuments. But the ancient Egyptians are known to have been in the habit
of enclosing with embankments the areas on which they erected temples,
statues, and obelisks, so as to exclude the waters of the Nile; and the
point of time to be ascertained, in every case where we find a monument
buried to a certain depth in mud, as at Memphis and Heliopolis, is the
era when the city fell into such decay that the ancient embankments were
neglected, and the river allowed to inundate the site of the temple,
obelisk, or statue.
Even if we knew the date of the abandonment of such embankments,
the enclosed areas would not afford a favourable opportunity for
ascertaining the average rate of deposit in the alluvial plain; for
Herodotus tells us that in his time those spots from which the Nile
waters had been shut out for centuries appeared sunk, and could be
looked down into from the surrounding grounds, which had been raised by
the gradual accumulation over them of sediment annually thrown down. If
the waters at length should break into such depressions, they must at
first carry with them into the enclosure much mud washed from the steep
surrounding banks, so that a greater quantity would be deposited in a
few years than perhaps in as many centuries on the great plain outside
the depressed area, where no such disturbing causes intervened.
ANCIENT MOUNDS OF THE VALLEY OF THE OHIO.
As I have already given several European examples of monuments of
prehistoric date belonging to the Recent period, I will now turn to
the American continent. Before the scientific investigation by Messrs.
Squier and Davis of the "Ancient Monuments of the Mississippi Valley",*
no one suspected that the plains of that river had been occupied, for
ages before the French and British colonists settled there, by a nation
of older date and more advanced in the arts than the Red Indians whom
the Europeans found there.
(* "Smithsonian Contributions" volume 1 1847.)
There are hundreds of large mounds in the basin of the Mississippi, and
especially in the valleys of the Ohio and its tributaries, which have
served, some of them for temples, others for outlook or defence, and
others for sepulture. The unknown people by whom they were constructed,
judging by the form of several skulls dug out of the burial-places, were
of the Mexican or Toltec race. Some of the earthworks are on so grand a
scale as to embrace areas of 50 or 100 acres within a simple enclosure,
and the solid contents of one mould are estimated at 20 million of cubic
feet, so that four of them would be more than equal in bulk to the Great
Pyramid of Egypt, which comprises 75 million. From several of these
repositories pottery and ornamental sculpture have been taken, and
various articles in silver and copper, also stone weapons, some composed
of hornstone unpolished, and much resembling in shape some ancient flint
implements found near Amiens and other places in Europe, to be alluded
to in the sequel.
It is clear that the Ohio mound-builders had commercial intercourse with
the natives of distant regions, for among the buried articles some are
made of native copper from Lake Superior, and there are also found mica
from the Alleghenies, sea-shells from the Gulf of Mexico, and obsidian
from the Mexican mountains.
The extraordinary number of the mounds implies a long period, during
which a settled agricultural population had made considerable progress
in civilisation, so as to require large temples for their religious
rites, and extensive fortifications to protect them from their enemies.
The mounds were almost all confined to fertile valleys or alluvial
plains, and some at least are so ancient that rivers have had time since
their construction to encroach on the lower terraces which support them,
and again to recede for the distance of nearly a mile, after having
undermined and destroyed a part of the works. When the first European
settlers entered the valley of the Ohio, they found the whole region
covered with an uninterrupted forest, and tenanted by the Red Indian
hunter, who roamed over it without any fixed abode, or any traditionary
connection with his more civilised predecessors. The only positive data
as yet obtained for calculating the minimum of time which must have
elapsed since the mounds were abandoned, have been derived from the age
and nature of the trees found growing on some of these earthworks. When
I visited Marietta in 1842, Dr. Hildreth took me to one of the mounds,
and showed me where he had seen a tree growing on it, the trunk of which
when cut down displayed eight hundred rings of annual growth.*
(* Lyell's "Travels in North America" volume 2 page 29.)
But the late General Harrison, President in 1841 of the United States,
who was well skilled in woodcraft, has remarked, in a memoir on this
subject, that several generations of trees must have lived and died
before the mounds could have been overspread with that variety of
species which they supported when the white man first beheld them, for
the number and kinds of trees were precisely the same as those which
distinguished the surrounding forest. "We may be sure," observed
Harrison, "that no trees were allowed to grow so long as the earthworks
were in use; and when they were forsaken, the ground, like all newly
cleared land in Ohio, would for a time be monopolised by one or two
species of tree, such as the yellow locust and the black or white
walnut. When the individuals which were the first to get possession of
the ground had died out one after the other, they would in many cases,
instead of being replaced by the same species, be succeeded (by virtue
of the law which makes a rotation of crops profitable in agriculture)
by other kinds, till at last, after a great number of centuries
(several thousand years, perhaps), that remarkable diversity of species
characteristic of North America, and far exceeding what is seen in
European forests, would be established."
MOUNDS OF SANTOS IN BRAZIL.
I will next say a few words respecting certain human bones embedded in
a solid rock at Santos in Brazil, to which I called attention in my
"Travels in North America" in 1842.*
(* Volume 1 page 200.)
I then imagined the deposit containing them to be of submarine
origin--an opinion which I have long ceased to entertain. We learn
from a memoir of Dr. Meigs that the River Santos has undermined a large
mound, 14 feet in height, and about 3 acres in area, covered with trees,
near the town of St. Paul, and has exposed to view many skeletons,
all inclined at angles between 20 and 25 degrees, and all placed in a
similar east and west position.*
(* Meigs "Transactions of the American Philosophical
Society" 1828 page 285.)
Seeing, in the Museum of Philadelphia, fragments of the calcareous stone
or tufa from this spot, containing a human skull with teeth, and in the
same matrix, oysters with serpulae attached, I at first concluded that
the whole deposit had been formed beneath the waters of the sea, or at
least, that it had been submerged after its origin, and again upheaved;
also, that there had been time since its emergence for the growth on it
of a forest of large trees. But after reading again, with more care, the
original memoir of Dr. Meigs, I cannot doubt that the shells, like
those of eatable kinds, so often accumulated in the mounds of the North
American Indians not far from the sea, may have been brought to the
place and heaped up with other materials at the time when the bodies
were buried. Subsequently, the whole artificial earthwork, with its
shells and skeletons, may have been bound together into a solid stone by
the infiltration of carbonate of lime, and the mound may therefore be
of no higher antiquity than some of those above alluded to on the Ohio,
which, as we have seen, have in like manner been exposed in the course
of ages to the encroachments and undermining action of rivers.
DELTA OF THE MISSISSIPPI.
I have shown in my "Travels in North America" that the deposits forming
the delta and alluvial plain of the Mississippi consist of sedimentary
matter, extending over an area of 30,000 square miles, and known in
some parts to be several hundred feet deep. Although we cannot estimate
correctly how many years it may have required for the river to bring
down from the upper country so large a quantity of earthy matter--the
data for such a computation being as yet incomplete--we may still
approximate to a minimum of the time which such an operation must have
taken, by ascertaining experimentally the annual discharge of water by
the Mississippi, and the mean annual amount of solid matter contained
in its waters. The lowest estimate of the time required would lead us
to assign a high antiquity, amounting to many tens of thousands of years
(probably more than 100,000) to the existing delta.
Whether all or how much of this formation may belong to the recent
period, as above defined, I cannot pretend to decide, but in one part of
the modern delta near New Orleans, a large excavation has been made
for gas-works, where a succession of beds, almost wholly made up of
vegetable matter, has been passed through, such as we now see forming
in the cypress swamps of the neighbourhood, where the deciduous cypress
(Taxodium distichum), with its strong and spreading roots, plays a
conspicuous part. In this excavation, at the depth of sixteen feet
from the surface, beneath four buried forests superimposed one upon
the other, the workmen are stated by Dr. B. Dowler to have found some
charcoal and a human skeleton, the cranium of which is said to belong to
the aboriginal type of the Red Indian race. As the discovery in question
had not been made when I saw the excavation in progress at the gas-works
in 1846, I cannot form an opinion as to the value of the chronological
calculations which have led Dr. Dowler to ascribe to this skeleton an
antiquity of 50,000 years. In several sections, both natural in the
banks of the Mississippi and its numerous arms, and where artificial
canals had been cut, I observed erect stumps of trees, with their roots
attached, buried in strata at different heights, one over the other. I
also remarked, that many cypresses which had been cut through, exhibited
many hundreds of rings of annual growth, and it then struck me that
nowhere in the world could the geologist enjoy a more favourable
opportunity for estimating in years the duration of certain portions of
the Recent epoch.*
(* Dowler cited by Dr. W. Usher in Nott and Gliddon's "Types
of Mankind" page 352.)
CORAL REEFS OF FLORIDA.
Professor Agassiz has described a low portion of the peninsula of
Florida as consisting of numerous reefs of coral, which have grown in
succession so as to give rise to a continual annexation of land, gained
gradually from the sea in a southerly direction. This growth is still
in full activity, and assuming the rate of advance of the land to be one
foot in a century, the reefs being built up from a depth of 75 feet, and
that each reef has in its turn added ten miles to the coast, Professor
Agassiz calculates that it has taken 135,000 years to form the southern
half of this peninsula. Yet the whole is of Post-Tertiary origin, the
fossil zoophytes and shells being all of the same species as those now
inhabiting the neighbouring sea.*
(* Agassiz in Nott and Gliddon ibid. page 352.)
In a calcareous conglomerate forming part of the above-mentioned series
of reefs, and supposed by Agassiz, in accordance with his mode of
estimating the rate of growth of those reefs, to be about 10,000 years
old, some fossil human remains were found by Count Pourtales. They
consisted of jaws and teeth, with some bones of the foot.
RECENT DEPOSITS OF SEAS AND LAKES.
I have shown, in the "Principles of Geology," where the recent changes
of the earth illustrative of geology are described at length, that the
deposits accumulated at the bottom of lakes and seas within the last
4000 or 5000 years can neither be insignificant in volume or extent.
They lie hidden, for the most part, from our sight; but we have
opportunities of examining them at certain points where newly-gained
land in the deltas of rivers has been cut through during floods, or
where coral reefs are growing rapidly, or where the bed of a sea or lake
has been heaved up by subterranean movements and laid dry.
As examples of such changes of level by which marine deposits of the
Recent period have become accessible to human observation, I have
adduced the strata near Naples in which the Temple of Serapis at
Pozzuoli was entombed.*
(* "Principles of Geology" Index "Serapis.")
These upraised strata, the highest of which are about 25 feet above the
level of the sea, form a terrace skirting the eastern shore of the Bay
of Baiae. They consist partly of clay, partly of volcanic matter, and
contain fragments of sculpture, pottery, and the remains of buildings,
together with great numbers of shells, retaining in part their colour,
and of the same species as those now inhabiting the neighbouring sea.
Their emergence can be proved to have taken place since the beginning of
the sixteenth century. [5]
In the same work, as an example of a freshwater deposit of the Recent
period, I have described certain strata in Cashmere, a country where
violent earthquakes, attended by alterations in the level of the ground,
are frequent, in which freshwater shells of species now inhabiting the
lakes and rivers of that region are embedded, together with the remains
of pottery, often at the depth of fifty feet, and in which a splendid
Hindoo temple has lately been discovered, and laid open to view by the
removal of the lacustrine silt which had enveloped it for four or five
centuries.
In the same treatise it is stated that the west coast of South America,
between the Andes and the Pacific, is a great theatre of earthquake
movements, and that permanent upheavals of the land of several feet at
a time have been experienced since the discovery of America. In various
parts of the littoral region of Chile and Peru, strata have been
observed enclosing shells in abundance, all agreeing specifically with
those now swarming in the Pacific. In one bed of this kind, in the
island of San Lorenzo, near Lima, Mr. Darwin found, at the altitude of
85 feet above the sea, pieces of cotton-thread, plaited rush, and the
head of a stalk of Indian corn, the whole of which had evidently been
embedded with the shells. At the same height, on the neighbouring
mainland, he found other signs corroborating the opinion that the
ancient bed of the sea had there also been uplifted 85 feet since the
region was first peopled by the Peruvian race. But similar shelly masses
are also met with at much higher elevations, at innumerable points
between the Chilean and Peruvian Andes and the sea-coast, in which
no human remains have as yet been observed. The preservation for an
indefinite period of such perishable substances as thread is explained
by the entire absence of rain in Peru. The same articles, had they been
enclosed in the permeable sands of an European raised beach, or in
any country where rain falls even for a small part of the year, would
probably have disappeared entirely [6]
In the literature of the eighteenth century, we find frequent allusion
to the "era of existing continents," a period supposed to have coincided
in date with the first appearance of Man upon the earth, since which
event it was imagined that the relative level of the sea and land had
remained stationary, no important geographical changes having occurred,
except some slight additions to the deltas of rivers, or the loss of
narrow strips of land where the sea had encroached upon its shores. But
modern observations have tended continually to dispel this delusion, and
the geologist is now convinced that at no given era of the past have the
boundaries of land and sea, or the height of the one and depth of the
other, or the geographical range of the species inhabiting them, whether
of animals or plants, become fixed and unchangeable. Of the extent to
which fluctuations have been going on since the globe had already become
the dwelling-place of Man, some idea may be formed from the examples
which I shall give in this and the next nine chapters.
UPHEAVAL SINCE THE HUMAN PERIOD OF THE CENTRAL DISTRICT OF SCOTLAND.
[7] It has long been a fact familiar to geologists, that, both
on the east and west coasts of the central part of Scotland, there are
lines of raised beaches, containing marine shells of the same species as
those now inhabiting the neighbouring sea.*
(* R. Chambers "Sea Margins" 1848 and papers by Mr. Smith of
Jordan Hill "Memoirs of the Wernerian Society" volume 8 and
by Mr. C. Maclaren. )
The two most marked of these littoral deposits occur at heights of about
50 and 25 feet above high-water mark, that of 50 feet being considered
as the more ancient, and owing its superior elevation to a continuance
of the upheaving movement. They are seen in some places to rest on the
boulder clay of the glacial period, which will be described in future
chapters.
In those districts where large rivers, such as the Clyde, Forth, and
Tay, enter the sea, the lower of the two deposits, or that of 25 feet,
expands into a terrace fringing the estuaries, and varying in breadth
from a few yards to several miles. Of this nature are the flat lands
which occur along the margin of the Clyde at Glasgow, which consist
of finely laminated sand, silt, and clay. Mr. John Buchanan, a zealous
antiquary, writing in 1855, informs us that in the course of the eighty
years preceding that date, no less than seventeen canoes had been dug
out of this estuarine silt, and that he had personally inspected a large
number of them before they were exhumed. Five of them lay buried in silt
under the streets of Glasgow, one in a vertical position with the prow
uppermost as if it had sunk in a storm. In the inside of it were a
number of marine shells. Twelve other canoes were found about 100 yards
back from the river, at the average depth of about 19 feet from the
surface of the soil, or 7 feet above high-water mark; but a few of them
were only 4 or 5 feet deep, and consequently more than 20 feet above
the sea-level. One was sticking in the sand at an angle of 45 degrees,
another had been capsized and lay bottom uppermost; all the rest were in
a horizontal position, as if they had sunk in smooth water.*
(* J. Buchanan "Report of the British Association" 1855 page
80; also "Glasgow, Past and Present" 1856.)
Almost every one of these ancient boats was formed out of a single
oak-stem, hollowed out by blunt tools, probably stone axes, aided by
the action of fire; a few were cut beautifully smooth, evidently with
metallic tools. Hence a gradation could be traced from a pattern of
extreme rudeness to one showing great mechanical ingenuity. Two of them
were built of planks, one of the two, dug up on the property of Bankton
in 1853, being 18 feet in length, and very elaborately constructed. Its
prow was not unlike the beak of an antique galley; its stern, formed of
a triangular-shaped piece of oak, fitted in exactly like those of our
day. The planks were fastened to the ribs, partly by singularly shaped
oaken pins, and partly by what must have been square nails of some kind
of metal; these had entirely disappeared, but some of the oaken pins
remained. This boat had been upset, and was lying keel uppermost,
with the prow pointing straight up the river. In one of the canoes, a
beautifully polished celt or axe of greenstone was found, in the bottom
of another a plug of cork, which, as Mr. Geikie remarks, "could only
have come from the latitudes of Spain, Southern France, or Italy."*
(* Geikie, "Quarterly Journal of the Geological Society"
volume 18 1862 page 224.)
There can be no doubt that some of these buried vessels are of far more
ancient date than others. Those most roughly hewn, may be relics of
the stone period; those more smoothly cut, of the bronze age; and the
regularly built boat of Bankton may perhaps come within the age of
iron. The occurrence of all of them in one and the same upraised marine
formation by no means implies that they belong to the same era, for
in the beds of all great rivers and estuaries, there are changes
continually in progress brought about by the deposition, removal, and
redeposition of gravel, sand, and fine sediment, and by the shifting of
the channel of the main currents from year to year, and from century
to century. All these it behoves the geologist and antiquary to bear in
mind, so as to be always on their guard, when they are endeavouring
to settle the relative date, whether of objects of art or of organic
remains embedded in any set of alluvial strata. Some judicious
observations on this head occur in Mr. Geikie's memoir above cited,
which are so much in point that I shall give them in full, and in his
own words.
"The relative position in the silt, from which the canoes were exhumed,
could help us little in any attempt to ascertain their relative ages,
unless they had been found vertically above each other. The varying
depths of an estuary, its banks of silt and sand, the set of its
currents, and the influence of its tides in scouring out alluvium
from some parts of its bottom and redepositing it in others, are
circumstances which require to be taken into account in all such
calculations. Mere coincidence of depth from the present surface of the
ground, which is tolerably uniform in level, by no means necessarily
proves contemporaneous deposition. Nor would such an inference follow
even from the occurrence of the remains in distant parts of the very
same stratum. A canoe might be capsized and sent to the bottom just
beneath low-water mark; another might experience a similar fate on
the following day, but in the middle of the channel. Both would become
silted up on the floor of the estuary; but as that floor would be
perhaps 20 feet deeper in the centre than towards the margin of the
river, the one canoe might actually be twenty feet deeper in the
alluvium than the other; and on the upheaval of the alluvial deposits,
if we were to argue merely from the depth at which the remains were
embedded, we should pronounce the canoe found at the one locality to be
immensely older than the other, seeing that the fine mud of the estuary
is deposited very slowly and that it must therefore have taken a long
period to form so great a thickness as 20 feet. Again, the tides and
currents of the estuary, by changing their direction, might sweep away a
considerable mass of alluvium from the bottom, laying bare a canoe that
may have foundered many centuries before. After the lapse of so long an
interval, another vessel might go to the bottom in the same locality and
be there covered up with the older one on the same general plane.
These two vessels, found in such a position, would naturally be classed
together as of the same age, and yet it is demonstrable that a very
long period may have elapsed between the date of the one and that of
the other. Such an association of these canoes, therefore, cannot be
regarded as proving synchronous deposition; nor, on the other hand, can
we affirm any difference of age from mere relative position, unless we
see one canoe actually buried beneath another."*
(* Geikie, "Quarterly Journal of the Geological Society"
volume 18 1862, page 222.)
At the time when the ancient vessels, above described, were navigating
the waters where the city of Glasgow now stands, the whole of the low
lands which bordered the present estuary of the Clyde formed the bed of
a shallow sea. The emergence appears to have taken place gradually and
by intermittent movements, for Mr. Buchanan describes several narrow
terraces one above the other on the site of the city itself, with steep
intervening slopes composed of the laminated estuary formation. Each
terrace and steep slope probably mark pauses in the process of upheaval,
during which low cliffs were formed, with beaches at their base. Five
of the canoes were found within the precincts of the city at different
heights on or near such terraces.
As to the date of the upheaval, the greater part of it cannot be
assigned to the stone period, but must have taken place after tools of
metal had come into use.
Until lately, when attempts were made to estimate the probable antiquity
of such changes of level, it was confidently assumed, as a safe
starting-point, that no alteration had occurred in the relative level
of land and sea, in the central district of Scotland, since the
construction of the Roman or Pictish wall (the "Wall of Antonine"),
which reached from the Firth of Forth to that of the Clyde. The two
extremities, it was said, of this ancient structure, bear such a
relation to the present level of the two estuaries, that neither
subsidence nor elevation of the land could have occurred for seventeen
centuries at least.
But Mr. Geikie has lately shown that a depression of 25 feet on the
Forth would not lay the eastern extremity of the Roman wall at Carriden
under water, and he was therefore desirous of knowing whether the
western end of the same would be submerged by a similar amount of
subsidence. It has always been acknowledged that the wall terminated
upon an eminence called the Chapel Hill, near the village of West
Kilpatrick, on the Clyde. The foot of this hill, Mr. Geikie estimates to
be about 25 or 27 feet above high-water mark, so that a subsidence of 25
feet could not lay it under water. Antiquaries have sometimes wondered
that the Romans did not carry the wall farther west than this Chapel
Hill; but Mr. Geikie now suggests, in explanation, that all the low land
at present intervening between that point and the mouth of the Clyde,
was sixteen or seventeen centuries ago, washed by the tides at high
water.
The wall of Antonine, therefore, yields no evidence in favour of the
land having remained stationary since the time of the Romans, but on
the contrary, appears to indicate that since its erection the land has
actually risen. Recent explorations by Mr. Geikie and Dr. Young, of the
sites of the old Roman harbours along the southern margin of the Firth
of Forth, lead to similar inferences. In the first place, it has long
been known that there is a raised beach containing marine shells of
living littoral species, at a height of about 25 feet, at Leith, as well
as at other places along the coast above and below Edinburgh. Inveresk,
a few miles below that city, is the site of an ancient Roman port,
and if we suppose the sea at high water to have washed the foot of the
heights on which the town stood, the tide would have ascended far up the
valley of the Esk, and would have made the mouth of that river a safe
and commodious harbour; whereas, had it been a shoaling estuary, as at
present, it is difficult to see how the Romans should have made choice
of it as a port.
At Cramond, at the mouth of the river Almond, above Edinburgh, was
Alaterva, the chief Roman harbour on the southern coast of the Forth,
where numerous coins, urns, sculptured stones and the remnant of a
harbour have been detected. The old Roman quays built along what must
then have been the sea margin, have been found on what is now dry land,
and although some silt carried down in suspension by the waters of the
Forth may account for a part of the gain of low land, we yet require
an upward movement of about 20 feet to explain the growth of the dreary
expanse of mud now stretching along the shore and extending outwards,
where it attains its greatest breadth, well-nigh two miles, across which
vessels, even of light burden, can now only venture at full tide. Had
these shoals existed eighteen centuries ago, they would have prevented
the Romans from selecting this as their chief port; whereas, if the
land were now to sink 20 feet, Cramond would unquestionably be the best
natural harbour along the whole of the south side of the Forth.*
(* Geikie, "Edinburgh New Philosophical Journal" for July
1861.)
Corresponding in level with the raised beach at Leith, above mentioned
(or about 25 feet above high-water mark), is the Carse of Stirling, a
low tract of land consisting of loamy and peaty beds, in which several
skeletons of whales of large size have been found. One of these was dug
up at Airthrie,* near Stirling, about a mile from the river, and 7 miles
from the sea.
(* Bald, "Edinburgh Philosophical Journal" 1 page 393 and
"Memoirs of the Wernerian Society" 3 page 327.)
Mr. Bald mentions that near it were found two pieces of stag's horn,
artificially cut, through one of which a hole, about an inch in
diameter, had been perforated. Another whale, 85 feet long, was found at
Dunmore, a few miles below Stirling,* which, like that of Airthrie, lay
about 20 feet above high-water mark.
(* "Edinburgh Philosophical Journal" 11 pages 220, 415.)
Three other skeletons of whales were found at Blair Drummond, between
the years 1819 and 1824, 7 miles up the estuary above Stirling,* also at
an elevation of between 20 and 30 feet above the sea. Near two of these
whales, pointed instruments of deer's horn were found, one of which
retained part of a wooden handle, probably preserved by having been
enclosed in peat. This weapon is now in the museum at Edinburgh.
(* "Memoirs of the Wernerian Society" volume 5 page 440.)
The position of these fossil whales and bone implements, and still more
of an iron anchor found in the Carse of Falkirk, below Stirling, shows
that the upheaval by which the raised beach of Leith was laid dry
extended far westward probably as far as the Clyde, where, as we have
seen, marine strata containing buried canoes rise to a similar height
above the sea.
The same upward movement which reached simultaneously east and west from
sea to sea was also felt as far north as the estuary of the Tay. This
may be inferred from the Celtic name of Inch being attached to many
hillocks, which rise above the general level of the alluvial plains,
implying that these eminences were once surrounded by water or marshy
ground. At various localities also in the silt of the Carse of Gowrie
iron implements have been found.
The raised beach, also containing a great number of marine shells of
recent species, traced up to a height of 14 feet above the sea by Mr.
W.J. Hamilton at Elie, on the southern coast of Fife, is doubtless
another effect of the same extensive upheaval.*
(* "Proceedings of the Geological Society" volume 2 1833
page 280.)
A similar movement would also account for some changes which antiquaries
have recorded much farther south, on the borders of the Solway Firth;
though in this case, as in that of the estuary of the Forth, the
conversion of sea into land has always been referred to the silting
up of estuaries, and not to upheaval. Thus Horsley insists on the
difficulty of explaining the position of certain Roman stations, on the
Solway, the Forth, and the Clyde, without assuming that the sea has been
excluded from certain areas which it formerly occupied.*
(* "Britannia" page 157 1860.)
On a review of the whole evidence, geological and archaeological,
afforded by the Scottish coast-line, we may conclude that the last
upheaval of 25 feet took place not only since the first human population
settled in the island; but long after metallic implements had come into
use, and there seems even a strong presumption in favour of the opinion
that the date of the elevation may have been subsequent to the Roman
occupation.
But the 25 feet rise is only the last stage of a long antecedent process
of elevation, for examples of Recent marine shells have been observed 40
feet and upwards above the sea in Ayrshire. At one of these localities,
Mr. Smith of Jordanhill informs me that a rude ornament made of cannel
coal has been found on the coast in the parish of Dundonald, lying 50
feet above the sea-level, on the surface of the boulder-clay or till,
and covered with gravel containing marine shells. If we suppose the
upward movement to have been uniform in central Scotland before and
after the Roman era, and assume that as 25 feet indicate seventeen
centuries, so 50 feet imply a lapse of twice that number, or 3400
years, we should then carry back the date of the ornament in question
to fifteen centuries before our era, or to the days of Pharaoh, and the
period usually assigned to the exodus of the Israelites from Egypt. [8]
But all such estimates must be considered, in the present state of
science, as tentative and conjectural, since the rate of movement of the
land may not have been uniform, and its direction not always upwards,
and there may have been long stationary periods, one of which of more
than usual duration seems indicated by the 50-foot raised beach, which
has been traced for vast distances along the western coast of Scotland.
COAST OF CORNWALL.
Sir H. De la Beche has adduced several proofs of changes of level,
in the course of the human period, in his "Report on the Geology of
Cornwall and Devon," 1839. He mentions (page 406) that several human
skulls and works of art, buried in an estuary deposit, were found in
mining gravel for tin at Pentuan, near St. Austell, the skulls lying at
the depth of 40 feet from the surface, and others at Carnon at the depth
of 53 feet. The overlying strata were marine, containing sea-shells
of living species, and bones of whales, besides the remains of several
living species of mammalia.
Other examples of works of art, such as stone hatchets, canoes,
and ships, buried in ancient river-beds in England, and in peat and
shell-marl, I have mentioned in my work before cited.
SWEDEN AND NORWAY.
In the same work I have shown that near Stockholm, in Sweden, there
occur, at slight elevations above the sea-level, horizontal beds
of sand, loam, and marl, containing the same peculiar assemblage of
testacea which now live in the brackish waters of the Baltic. Mingled
with these, at different depths, have been detected various works of art
implying a rude state of civilization, and some vessels built before the
introduction of iron, and even the remains of an ancient hut, the
marine strata containing it, which had been formed during a previous
depression, having been upraised, so that the upper beds are now 60 feet
higher than the surface of the Baltic. In the neighbourhood of these
recent strata, both to the north-west and south of Stockholm, other
deposits similar in mineral composition occur, which ascend to greater
heights, in which precisely the same assemblage of fossil shells is met
with, but without any intermixture, so far as is yet known, of human
bones or fabricated articles.
On the opposite or western coast of Sweden, at Uddevalla, Post-Tertiary
strata, containing recent shells, not of that brackish water character
peculiar to the Baltic, but such as now live in the Northern Ocean,
ascend to the height of 200 feet; and beds of clay and sand of the same
age attain elevations of 300 and even 600 feet in Norway, where they
have been usually described as "raised beaches." They are, however,
thick deposits of submarine origin, spreading far and wide, and filling
valleys in the granite and gneiss, just as the Tertiary formations, in
different parts of Europe, cover or fill depressions in the older rocks.
Although the fossil fauna characterising these upraised sands and clays
consists exclusively of existing northern species of testacea, it is
more than probable that they may not all belong to that division of the
Pleistocene strata which we are now considering. If the contemporary
mammalia were known, they would, in all likelihood, be found to be
referable, at least in part, to extinct species; for, according to Loven
(an able living naturalist of Norway), the species do not constitute
such an assemblage as now inhabits corresponding latitudes in the North
Sea. On the contrary, they decidedly represent a more arctic fauna. In
order to find the same species flourishing in equal abundance, or
in many cases to find them at all, we must go northwards to higher
latitudes than Uddevalla in Sweden, or even nearer the pole than Central
Norway.
Judging by the uniformity of climate now prevailing from century to
century, and the insensible rate of variation in the geographical
distribution of organic beings in our own times, we may presume that
an extremely lengthened period was required even for so slight a
modification in the range of the molluscous fauna, as that of which
the evidence is here brought to light. There are also other independent
reasons for suspecting that the antiquity of these deposits may be
indefinitely great as compared to the historical period. I allude to
their present elevation above the sea, some of them rising, in Norway,
to the height of 600 feet or more. The upward movement now in progress
in parts of Norway and Sweden extends, as I have elsewhere shown,*
throughout an area about 1000 miles north and south, and for an unknown
distance east and west, the amount of elevation always increasing as we
proceed towards the North Cape, where it is said to equal 5 feet in a
century.
(* "Principles" 9th edition chapter 30.)
If we could assume that there had been an average of 2 1/2 feet in each
hundred years for the last fifty centuries, this would give an elevation
of 125 feet in that period. In other words, it would follow that the
shores, and a considerable area of the former bed of the North Sea, had
been uplifted vertically to that amount, and converted into land in
the course of the last 5000 years. A mean rate of continuous vertical
elevation of 2 1/2 feet in a century would, I conceive, be a high
average; yet, even if this be assumed, it would require 24,000 years for
parts of the sea-coast of Norway, where the Pleistocene marine strata
occur, to attain the height of 600 feet. [9]