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which have taken place principally in volcanic districts, have not ex-
ceeded a few feet in historical times.

The deltas of rivers have increased, and the sea has sometimes eroded
and sometimes added to the outline of coasts, but there has been no
change for more than 2000 years in the general level of sea and land in
any of the districts known to the ancient world. The spit of shingle
which connects St. Michael's Mount with Cornwall, is still covered at
flood and dry at ebb tide, as when the ancient Britons carted their tin
across it to barter with Tyrian merchants. Marseilles is a sea-port, as it



PROBLEMS OF THE FUTURE. 53

was when the Phocaean galleys entered its harbor. In Egypt it is evi-
dent that no considerable change of level, either of the land or of the
Mediterranean, can have occurred since Menes embanked the Nile 7000

years ago.

The only authentic record we have of the rise or fall of masses of land
as ascertained by actual measurement, are those of Scandinavia and South
America. The Pacific shore of the latter was upheaved five or six feet
for a distance of 500 or 600 miles, by the shock of a single earthquake,
and remains of human art, such as plaited rushes and string, have been
found in a bed of marine shells near Callao, showing that this part of
the continent had been elevated eighty-five feet since it was inhabited by
man. This, however, gives no clue to the rate of elevation, since we
know nothing of the date of man's appearance in Peru, and the whole
area is one of volcanic disturbance, which has been raised by successive
earthquake shocks, and not by gradual elevation.

In the case of Scandinavia, however, where raised beaches up to the
height of 600 feet above the sea level afford proof of much recent eleva-
tion, and where there are no signs of volcanic action, attempts have been
made to measure the rate accurately by marks cut on rocks. The results,
carefully considered by Sir C. Lyell, show a slow, uniform rate of eleva-
tion of two or three feet in a century, where the rate is at its maximum
at Gefle, ninety miles north of Stockholm, which dies out towards the
North Cape, and is converted into a slow depression in the south of
Sweden. At this rate of three feet per century the depression which
carried the hills of Wales and Scotland 2000 feet down would have re-
quired 66,666 years, and its elevation an equal period, so that without
any allowance for the time the sea-bottom may have remained stationary,
this interlude of the Glacial period would have required 133,333 years.
Of course, it is not implied that this was the real time, or that the rate
both of elevation and depression may not have been faster ; but all the
evidence points to its having been gradual and not paroxysmal, as there
are no traces of any contemporaneous earthquakes or volcanoes in Wales
or Scotland. And whatever the rate may have been it is scarcely pos-
sible to suppose that it can have been such as to enable us to compress
the whole Glacial and Post-Glacial periods, of which this was only one
of the intermediate phases, within anything like the limits of from 25,000
to 35,000 years assigned to them by Professor Prestwich. On the con-
trary, all the evidence from existing known facts points rather to an ex-
tension than to a contraction of the time assigned by Lyell and Croll,
and if the theory of the latter is correct, it would almost seem as if his
first period of maximum refrigeration, 700,000 years ago, was that of the
formation of the first great ice-cap. And whatever the time may be, it is
clear that in its earlier stages man was already widely distributed over the
earth, while there is the strongest probability that his origin must have



S4 BEACON LIGHTS OF SCIENCE.

taken place very much further back in the Pliocene or even in the Mio-
cene period.

It must always be remembered that while the date of human origins in
years or centuries is a question of great scientific interest, it makes little
difference, as regards the religious and philosophical aspects of the ques-
tion, whether it extends over 50,000 or 500,000 years. In any case, the
fact is beyond question, that it is one of immense antiquity, far trans-
cending any period recorded by history or tradition, and that during this
immense period the course of humanity has been upward and not down-
ward. Man has not fallen but risen, and arts, morals, societies, and civ-
ilization have been slowly developed from an animal-like condition of the
lowest savagery.

Perhaps the issue between the long and short dates of the Glacial pe-
riod can be most closely joined if we take that portion of it which comes
nearest to historical times, and is known as the Post-Glacial. Prestwich
assigns to this period a duration of " 8000 to 10,000 years or less," that is a
duration of not more than 2000 or 3000 years before the time when we
know for certain that a dense population and high civilization already
existed in Egypt and Chaldaea. I am not aware that he assigns any rea-
son for this highly improbable date, except the conjecture that the erosion
of river valleys may have gone on more rapidly, owing to a greater rain-
fall.

Now the duration of this Post Glacial period is a question, not of con-
jecture or theory, but of a vast number of definite and measurable facts.
In the British Islands these facts have been carefully examined and ascer-
tained with great accuracy, mainly by the labors of the Geological Survey.
An eminent officer of this Survey, Mr. T. Mellard Reade, who has
worked for many years at these beds in Lancashire and Cheshire, and is
one of the best authorities on the subject, read, as recently as in February,
1888, a paper before the Geological Society, in which he gave a minute
description of the successive changes in Post-Glacial times, by which the
Mersey valley and estuary were brought into their present condition, with
an estimate of the time they may have required. His estimate is " that
in round figures 60,000 years for Post-Glacial time is a reasonable one and,
as represented by these changes, well within the mark."

This is not a random estimate, but based on a careful calculation of
the different changes which are shown by sections and borings to have
actually taken place. At the close of the Glacial period the district was
submerged, and the valleys of the old Pre-Glacial rivers were levelled up
to a height of at least 200 feet by marine boulder-clay. The land then
rose until its surface became an undulating upland plain, through which
tne present rivers began to cut the existing valleys. A mass of boulder-
clav 200 feet in depth, and several miles in width, must thus have been
removed by sub-aerial denudation before the next stage, which consisted
of a general depression of the area, as is proved by the fact that borings



PROBLEMS OF THE FUTURE. 55

show a series of estuarine deposits with marine shells in places fifty feet
thick, overlying the boulder-clay, and levelling up the inequalities of its
surfac: due to sub-aerial erosion. Above these silts and clays is a peat-
bed containing stools of trees with their roots running down into the
clays below. This is a remarkable deposit, for a similar submerged
forest bed is to be traced all round the shores of the British Islands, from
Devonshire to the Orkneys. Evidently at a recent period, geologically
speaking there has been an age of forests which flourished, and in their
decay formed great beds of peat, in localities where no trees have grown,
within the Historical period. Before these forests could have grown,
the marine silts and clays must have been elevated above the sea to a
sufficient height to become dry land and covered with trees, and the cli-
mate must have been very different from that at present prevailing. It
must have been more of a continental and less of an insular climate, and
in all probability the German Ocean was then dry land, and the British
Islands were connected with an Europe which extended westward up to
i oo fathom line. In no other way can the existence of surmerged forests,
and vast masses of peat with remains of trees, be accounted for in such
isolated islands as those of Orkney and Shetland, now swept by ocean
blasts, and where no vestige of a tree has grown for at least 2000 years,
when a Roman author described them as "carentes sylva,"

But at whatever height the land may have stood during this Forest
period, it is evident that it must have subsided, at any rate to the extent
necessary to bring the submerged forests to their present level of some feet
below low-water mark. Or, indeed, some twenty-four feet more, for there
is evidence that a rise to this extent has taken place, quite recently, along
a considerable portion of the British coast, as shown by raised beaches.
When I say recently, I mean in geological time, for in historical time
there has been no appreciable change of level since the occupation of
Britain by the Romans, or for nearly 2000 years.

In other regions, however, we have still more conclusive evidence of
the great length of time which has elapsed since any appreciable change
has taken place in the physical geography of Europe, and in the present
relative levels of sea and land. The localities described by Homer in the
Odyssey can be identified, and the very cave and beach pointed out in
Ithaca, on which Ulysses was landed by the Phoenician mariners. The
annals of Egypt carry us back still farther, and show that no appre-
ciable change can have taken place in the levels of sea and land in the
Eastern Mediterranean, for at least 7000 years, and probably for much
longer.

With these facts, even if we had no other evidence than that of the
submerged forests, Professor Prestwich's estimate of 8000 to 10,000 years
for the whole Post-Glacial period down to the present time seems totally
inadequate, and Mr. Mellard Reade's of 60,000 years much more prob-
able. In fact, it seems impossible that changes, such as those demon-



56 BEACON LIGHTS OF SCIENCE.

strated to have occurred in the Mersey valley, can have been accomplished
within a period shorter than that which is shown by historical records to
have elapsed in Egypt without perceptible change.

But whether the duration of the Post-Glacial period be more or less, it
is evidently a small fraction of the time which is required to account for
the work done during the preceding Glacial period, or rather periods, for
there is distinct evidence that there were several advances and retreats of
the ice-sheets, and alternations of climates, during some of which the
winter temperature of Western Europe must have been higher than it is at
present The succession of ice-sheets is clearly shown by the sections
afforded by the coast cliffs of the east of England, where four successive
boulder-clays are shown, separated by masses of sand and gravel deposited
during the melting and retreat of each ice-sheet. The alternations of
mild Inter-Glacial with severe Glacial periods, is shown by the frequent
presence in caves of a Southern fauna, some of which, like the hippopot-
amus which is found as far north as Yorkshire could by no possibility
have lived in a country where the lakes and rivers were bound in ice for a
great part of the year. And still more conclusively by the presence, in
the south of France, of a vegetation comprising the fig-tree and delicate
Canary laurel, in the region over which, at another period of the Glacial
age, herds of reindeer roamed, feeding on lichens and Arctic-willows, and
accompanied by the musk-ox, the glutton, the lemming, and other ex-
clusively Arctic animals.

But although the evidence for the great antiquity of the Glacial period
seems to be conclusive, it must be confessed that we are as far as ever
from being able to assign any reliable explanation of the causes which
produced it. It came on suddenly, for the interval between the temper-
ate Pliocene and the extreme rigor of the first great ice-sheet is, geolog-
ically speaking, very short Only a few feet of clay and sand separate
the Cromer forest, in which the great southern elephant, the Elephas
Meridionalis, and other southern mammalia roamed, from the boulder-
clay of the Scandinavian ice-sheet, which carried rocks from Lapland and
Norway, across the North Sea and over hills and valleys almost to the
centre of Europe. This first period was the coldest, and after several os-
cillations of heat and cold, each apparently less intense than its predeces-
sor, the climate of the Northern hemisphere finally settled down to its
present conditions.

These facts seem to negative most of the theories, or rather guesses,
which have been hazarded to account for this great and sudden refriger-
ation. It could not be due to any cooling of the earth, for this must
have been gradual and progressive, and the great cold of the first period
instead of decreasing and disappearing, must have gone on increasing.
It has been supposed that the solar system, on its journey through space,
may have entered into, and emerged from, regions very much colder than
those of former ages or at present, but such a cause is at present little



PROBLEMS OF THE FUTURE. 5/

more than a conjecture. Nor is it possible that any alteration in the po-
sition of the earth's axis can have occurred within the earth, for this
would have disarranged its equatorial protuberance, which is precisely
that of a fluid mass, rotating about the present axis, and could not be
altered without producing a complete cataclysm. No one can suppose
that an equatorial protuberance of more than 20 miles can have been
shifted through many degrees of latitude, during the short interval be-
tween the close of the Pliocene and the commencement of the Glacial
period.

Neither can the theories which have been applied to earlier geological
epochs, of a warmer blanket of watery vapor and carbonic-dioxide in
the atmosphere, account for such a sudden refrigeration and its gradual
disappearance. The conditions under which the Pre-Glacial Cromer
forest flourished, and tho:e at present exisiting in the same locality, can-
not have been so different as to imply a new order of cosmic or telluric
causes.

There remain only two at all plausible theories, the astronomical one
of Croll, and that of Lyell, who explains everything by a different config-
uration of sea and land. Croll's theory explains many of the facts ad-
mirably, but, as we have seen, it cannot be accepted with confidence, in
the absence of proof that a succession of Glacial periods has occurred in
previous geological epochs. Nor is it very consistent with the fact that
the cold period come on suddenly, and was greatest at first ; while if due
to the eccentricity of the earth's orbit, it ought to have come on gradu-
ally, and only attained its maximum simultaneously with that of the ec-
centricity. Lyell's theory is on the whole most generally accepted, as
actual experience shows that high land in high latitudes is a cause of
glacial conditions, and also that oceanic currents are a main factor in
producing climate.

When we inquire under what conditions great glaciers are now formed,
we find them to be mainly heavy snow-fall conbined with low tempera-
ture. Thus the snow-fall is very heavy on the Pacific slope of the Sierra
Nevada and coast range of Northern California and British Columbia;
but it does not, as formerly, produce glaciers, because the temperature is
not low enough to convert the winter snow into the frozen " neVe " which
is the source of glaciers, and to produce the conditions under which the
accumulation finds its way to lower levels by solid rather than by fluid
rivers. Again, extreme cold does not of itself produce glaciers, as is seen
in Northern Russia and Siberia. The influence of ocean-currents is also
apparent from the effects of the Gulf Stream, which gives open winters to
the coasts and islands of Western Europe, in a latitude as high as that
of the southern extremity of Greenland.

Here, then, are real causes which may account for such a Glacial
period as has been experienced, without invoking utterly unknown and
conjectural theories. But there are considerable difficulties in the way of



5 8 BEACON LIGHTS OF SCIENCE.

accepting Lyell's theory as the sole and sufficient explanation. The sud-
denness with which the great cold came on is one of them. It is difficult
to suppose that such a great elevation of land in the North Atlantic as
would be required, took place, almost at once, in the short interval in
which the Pliocene passed almost continuously into the Quaternary. We
are tolerably certain, from the similarity of the fauna and flora, that
America was connected with the Old Continent during the Miocene period
by a land passage across the North Atlantic, and yet there are no traces of
a rigorous climate. On the contrary, a climate almost sub-tropical pre-
vailed then in Greenland and Spitzbergen, far within the Arctic Circle.

Again, the Gulf Stream must always have been an important factor in
determining the climate, but recent theories as to the great geological
antiquity of the Atlantic Ocean make it difficult to conceive how this
Stream can have been greatly diverted from its present course, in recent
geological times. And the fact that the ice-cap extended much farther to
the south in North America than in Europe, makes it almost certain that
the influence of the warm Gulf and cold Polar streams must have been
felt during the Glacial period, as they are now. How otherwise can we
account for the fact that the difference of temperature between Europe
and America seems to have been almost the same during the period of
extreme cold in both, as it is now under temperate conditions ? And the
diversion of the Gulf Stream would certainly tend to produce less evap-
oration in the North Atlantic, and therefore less fall of rain or snow on
Northern lands, whereas the contrary is required to account for the ice-
caps. We must conclude, therefore, that while Lyell's theory affords the
most probable explanation, we are still in a state of great uncertainty as
to the causes which may have co-operated in bringing about the last and
greatest vicissitude of climate, the Glacial period, which is so interesting
to us from its close connection with the origin of man. The causes and
duration of the last Glacial period, and whether there have been several,
and if so, how many of such periods in former geological ages, are among
the problems of the future which are pressing for solution.



CHAPTER V.
TERTIARY MAN.

OF all the discoveries of modern science, that of the antiquity of man
has been the most startling. It is not like the abstract discoveries
of astronomy and geology, which only indirectly affect the unscientific
mass of mankind. It shatters at a blow what had been for centuries the
axioms of the whole Christian world, respecting the origin of man, his
place in creation, and the course of his development A literal acceptance
of the dates and narrative of Genesis was assumed to be the sole basis of
knowledge on the subject, and to question what was told by a Divine
revelation was universally considered to be alike ridiculous and impious.

As far as science had a word to say it was thought to confirm theology,
for did not Cuvier himself lay down as an axiom that no human remains
had been found in a fossil state, or in conjunction with the remains of any
of the extinct animals ? And although a few scientific men here and
there, basing their ideas mainly on the dates of Egyptian monuments,
pleaded for a somewhat longer period than the date assigned by Arch-
bishop Usher, there may fairly be said to have been a universal consensus
of opinion among all men, learned or unlearned, that the existence of the
human race on our planet had not lasted longer than some 6000 or 7000
years before the present period. This was the universal opinion only
thirty years ago, wnen in 1859 Mr. Prestwich read his memorable paper
to the Royal Society, confirming the discoveries of M. Boucher de Perthes,
and proving beyond a possibility of doubt that flint implements, fashioned
by human hands, were found in Quaternary gravels, and brick-earths of
the valley of the Somme, in juxtaposition with remains of the mammoth
and other extinct animals, which must have been deposited when the river
ran at more than 100 feet above its present level. The careful explora-
tion of the Devonshire caves of Brixham and Kent's Hole, by committees
of competent geologists, removed the last doubts on the subject, and since
then, evidence has accumulated so rapidly from all quarters of the world,
that the existence of Quaternary man has become as certain a fact as that
the earth revolves round its axis.

Consider what this implies. The Tertiary epoch, in which mammalian
life for the first time appears prominently and an approximation is made
to existing conditions, is itself but a small fraction of the succession of

59



60 BEACON LIGHTS OF SCIENCE.

geological ages since our planet became the abode of animal and vegeta-
ble life. At the outside, its three divisions of Eocene, Miocene, and
Pliocene, may together represent one-twentieth part of the thickness of
fossiliferous strata from the Cambrian to the Cretaceous. The Quaternary
period again is but a fraction of the Tertiary; and the recent or existing
epoch, including the Historic and Pre-Historic, is but a fraction of the
Quaternary. The recent or Historical epoch, characterized by the exist-
ing fauna, and, in the main, by the existing climate and disposition of
sea and land, is certainly not less than 7000 years old, when Egyptian
records and monuments shows us a populous and highly civilized nation
already existing in the valley of the Nile, and civilized empires of almost
as early a date in Chaldaea and China. The Pre-Historic period, charac-
terized by the existing fauna and by neolithic man, must have lasted much
longer, before such empires could have been developed from the rude and
primitive civilization shown by the Scandinavian Kjokken-middens, the
Swiss Lake-dwellings, and other early records of the Neolithic period.
Borings in the Nile valley have everywhere brought up rude pottery, and
other neolithic remains, from depths below the foundations of the oldest
historical monuments, which, at the present rate of silting up by the
annual inundations of the river, imply an antiquity of about 18,000 years.
This may not be quite accurate as a chronological standard in years, but
undoubtedly this, and other similar calculations from physical changes
during the Neolithic period, ",11 point to the conclusion that 15,000 or
20,000 years is the shortest time that can have elapsed since its commence-
ment

Then comes a great break. The climate, geographical and physical
conditions, and fauna, have undergone great changes when we next meet
with traces of man, and the Quaternary period stretches back into the
Pliocene, through an immense though unknown duration of time. This
much however is known, that it embraces two, if not more, great Glacial
periods, during the first and most severe of which the northern halves of
Europe and America were buried under an ice-cap, in places 5000 or 6000
feet thick, resembling that of modern Greenland, and driving all terrestrial
life before it into more southern regions. These Glacial periods alternated
with long Inter-Glacial ages, when the ice retreated, and vegetation and
animal life again returned to their old abodes, and again advanced and
retreated, finally occupying their present stations when the glaciers had
shrunk into the valleys of the loftier mountains.

It is certain also that vast changes in the physical geography, and con-
figuration of sea, land, and rivers, occurred during this period. The
British Islands, or a large portion of them, were at one time submerged
to a depth of certainly 1500, and probably 2000 or 2500 feet beneath an
Arctic sea, presenting nothing above it but an archipelago, of what are now
mountain peaks; while at another time they were part of an European
continent, then connected with Africa, and across which huge extinct



PROBLEMS OF THE FUTURE. 61

lions, tigers, bears, elephants, and rhinoceroses roamed, and left their
remains in the caves of limestone districts, and the sands and gravels or
rivers, when they flowed 100 feet or more above their present level.
During part of this period a southern fauna, and even the hippopotamus,
found their way as far north as Yorkshire, testifying to the existence
of great rivers flowing from the south across this Quaternary continent



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