If you, dear reader, dwell in any northern town, you will almost
certainly see paving courts and alleys, and sometimes--to the
discomfort of your feet--whole streets, or set up as bournestones at
corners, or laid in heaps to be broken up for road-metal, certain
round pebbles, usually dark brown or speckled gray, and exceedingly
tough and hard. Some of them will be very large--boulders of several
feet in diameter. If you move from town to town, from the north of
Scotland as far down as Essex on the east, or as far down as
Shrewsbury and Wolverhampton (at least) on the west, you will still
find these pebbles, but fewer and smaller as you go south. It
matters not what the rocks and soils of the country round may be.
However much they may differ, these pebbles will be, on the whole,
the same everywhere.
But if your town be south of the valley of the Thames, you will find,
as far as I am aware, no such pebbles there. The gravels round you
will be made up entirely of rolled chalk flints, and bits of beds
immediately above or below the chalk. The blocks of "Sarsden"
sandstone--those of which Stonehenge is built--and the "plum-pudding
stones" which are sometimes found with them, have no kindred with the
northern pebbles. They belong to beds above the chalk.
Now if, seeing such pebbles about your town, you inquire, like a
sensible person who wishes to understand something of the spot on
which he lives, whence they come, you will be shown either a gravel-
pit or a clay-pit. In the gravel the pebbles and boulders lie mixed
with sand, as they do in the railway cutting just south of
Shrewsbury; or in huge mounds of fine sweet earth, as they do in the
gorge of the Tay about Dunkeld, and all the way up Strathmore, where
they form long grassy mounds--tomauns as they call them in some parts
of Scotland--askers as they call them in Ireland. These mounds, with
their sweet fresh turf rising out of heather and bog, were tenanted--
so Scottish children used to believe--by fairies. He that was lucky
might hear inside them fairy music, and, the jingling of the fairy
horses' trappings. But woe to him if he fell asleep upon the mound,
for he would be spirited away into fairyland for seven years, which
would seem to him but one day. A strange fancy; yet not so strange
as the actual truth as to what these mounds are, and how they came
into their places.
Or again, you might find that your town's pebbles and boulders came
out of a pit of clay, in which they were stuck, without any order or
bedding, like plums and raisins in a pudding. This clay goes usually
by the name of boulder-clay. You would see such near any town in
Cheshire and Lancashire; or along Leith shore, near Edinburgh; or, to
give one more instance out of hundreds, along the coast at
Scarborough. If you walk along the shore southward of that town, you
will see, in the gullies of the cliff, great beds of sticky clay,
stuffed full of bits of every rock between the Lake mountains and
Scarborough, from rounded pebbles of most ancient rock down to great
angular fragments of ironstone and coal. There, as elsewhere, the
great majority of the pebbles have nothing to do with the rock on
which the clay happens to lie, but have come, some of them, from
places many miles away.
Now if we find spread over a low land pebbles composed of rocks which
are only found in certain high lands, is it not an act of common
sense to say--These pebbles have come from the highlands? And if the
pebbles are rounded, while the rocks like them in the highlands
always break off in angular shapes, is it not, again, an act of mere
common sense to say--These pebbles were once angular, and have been
rubbed round, either in getting hither or before they started hither?
Does all this seem to you mere truism, my dear reader? If so, I am
sincerely glad to hear it. It was not so very long ago that such
arguments would have been considered not only no truisms, but not
even common sense.
But to return, let us take, as an example, a sample of these boulder
clay pebbles from the neighbourhood of Liverpool and Birkenhead, made
by Mr. De Rance, the government geological surveyor:
Granite, greenstone, felspar porphyry, felstone, quartz rock (all
igneous rocks, that is, either formed by, or altered by volcanic
heat, and almost all found in the Lake mountains), 37 per cent.
Silurian grits (the common stones of the Lake mountains deposited by
water), 43 per cent.
Ironstone, 1 per cent.
Carboniferous limestone, 5 per cent.
Permian or Triassic sandstones, i.e. rocks immediately round
Liverpool, 12 per cent.
Now, does not this sample show, as far as human common sense can be
depended on, that the great majority of these stones come from the
Lake mountains, sixty or seventy miles north of Liverpool? I think
your common sense will tell you that these pebbles are not mere
concretions; that is, formed out of the substance of the clay after
it was deposited. The least knowledge of mineralogy would prove
that. But, even if you are no mineralogist, common sense will tell
you, that if they were all concreted out of the same clay, it is most
likely that they would be all of the same kind, and not of a dozen or
more different kinds. Common sense will tell you, also, that if they
were all concreted out of the same clay, it is a most extraordinary
coincidence, indeed one too strange to be believed, if any less
strange explanation can be found--that they should have taken the
composition of different rocks which are found all together in one
group of mountains to the northward. You will surely say--If this be
granite, it has most probably come from a granite mountain; if this
be grit, from a grit-stone mountain, and so on with the whole list.
Why--are we to go out of our way to seek improbable explanations,
when there is a probable one staring us in the face?
Next--and this is well worth your notice--if you will examine the
pebbles carefully, especially the larger ones, you will find that
they are not only more or less rounded, but often scratched; and
often, too, in more than one direction, two or even three sets of
scratches crossing each other; marked, as a cat marks an elder stem
when she sharpens her claws upon it; and that these scratches have
not been made by the quarrymen's tools, but are old marks which
exist--as you may easily prove for yourself--while the stone is still
lying in its bed of clay. Would it not be an act of mere common
sense to say--These scratches have been made by the sharp points of
other stones which have rubbed against the pebbles somewhere, and
somewhen, with great force?
So far so good. The next question is--How did these stones get into
the clay? If we can discover that, we may also discover how they
wore rounded and scratched. We must find a theory which will answer
our question; and one which, as Professor Huxley would say, "will go
on all-fours," that is, will explain all the facts of the case, and
not only a few of them.
What, then, brought the stones?
We cannot, I think, answer that question, as some have tried to
answer it, by saying that they were brought by Noah's flood. For it
is clear, that very violent currents of water would be needed to
carry boulders, some of them weighing many tons, for many miles. Now
Scripture says nothing of any such violent currents; and we have no
right to put currents, or any other imagined facts, into Scripture
out of our own heads, and then argue from them as if not we, but the
text of Scripture had asserted their existence.
But still, they may have been rolled hither by water. That theory
certainly would explain their being rounded; though not their being
scratched. But it will not explain their being found in the clay.
Recollect what I said in my first paper: that water drops its
pebbles and coarser particles first, while it carries the fine clayey
mud onward in solution, and only drops it when the water becomes
still. Now currents of such tremendous violence as to carry these
boulder stones onward, would have carried the mud for many miles
farther still; and we should find the boulders, not in clay, but
lying loose together, probably on a hard rock bottom, scoured clean
by the current. That is what we find in the beds of streams; that is
just what we do not find in this case.
But the boulders may have been brought by a current, and then the
water may have become still, and the clay settled quietly round them.
What? Under them as well as over them? On that theory also we
should find them only at the bottom of the clay. As it is, we find
them scattered anywhere and everywhere through it, from top to
bottom. So that theory will not do. Indeed, no theory will do which
supposes them to have been brought by water alone.
Try yourself, dear reader, and make experiments, with running water,
pebbles, and mud. If you try for seven years, I believe, you will
never contrive to make your pebbles lie about in your mud, as they
lie about in every pit in the boulder clay.
Well then, there we are at fault, it seems. We have no explanation
drawn from known facts which will do--unless we are to suppose, which
I don't think you will do, that stones, clay, and all were blown
hither along the surface of the ground, by primeval hurricanes, ten
times worse than those of the West Indies, which certainly will roll
a cannon a few yards, but cannot, surely, roll a boulder stone a
hundred miles.
Now, suppose that there was a force, an agent, known--luckily for
you, not to you--but known too well to sailors and travellers; a
force which is at work over the vast sheets of land at both the north
and south poles; at work, too, on every high mountain range in the
world, and therefore a very common natural force; and suppose that
this force would explain all the facts, namely--
How the stones got here;
How they were scratched and rounded;
How they were imbedded in clay;
because it is notoriously, and before men's eyes now, carrying great
stones hundreds of miles, and scratching and rounding them also;
carrying vast deposits of mud, too, and mixing up mud and stones just
as we see them in the brick-pits,--Would not our common sense have a
right to try that explanation?--to suspect that this force, which we
do not see at work in Britain now, may have been at work here ages
since? That would at least be reasoning from the known to the
unknown. What state of things, then, do we find among the highest
mountains; and over whole countries which, though not lofty, lie far
enough north or south to be permanently covered with ice?
We find, first, an ice-cap or ice-sheet, fed by the winter's snows,
stretching over the higher land, and crawling downward and outward by
its own weight, along the valleys, as glaciers.
We find underneath the glaciers, first a moraine profonde, consisting
of the boulders and gravel, and earth, which the glacier has ground
off the hillsides, and is carrying down with it.
These stones, of course, grind, scratch, and polish each other; and
in like wise grind, scratch, and polish the rock over which they
pass, under the enormous weight of the superincumbent ice.
We find also, issuing from under each glacier a stream, carrying the
finest mud, the result of the grinding of the boulders against each
other and the glacier.
We find, moreover, on the surface of the glaciers, moraines
superieures--long lines of stones and dirt which had fallen from
neighbouring cliffs, and are now travelling downward with the
glaciers.
Their fate, if the glacier ends on land, is what was to be expected.
The stones from above the glacier fall over the ice-cliff at its end,
to mingle with those thrown out from underneath the glacier, and form
huge banks of boulders, called terminal moraines, while the mud runs
off, as all who have seen glaciers know, in a turbid torrent.
Their fate, again, is what was to be expected if the glacier ends, as
it commonly does in Arctic regions, in the sea. The ice grows out to
sea-ward for more than a mile sometimes, about one-eighth of it being
above water, and seven-eighths below, so that an ice-cliff one
hundred feet high may project into water eight hundred feet deep. At
last, when it gets out of its depth, the buoyancy of the water breaks
it off in icebergs, which float away, at the mercy of tides and
currents, often grounding again in shallower water, and ploughing the
sea-bottom as they drag along it. These bergs carry stones and dirt,
often in large quantities; so that, whenever a berg melts or
capsizes, it strews its burden confusedly about the sea-floor.
Meanwhile the fine mud which is flowing out from under the ice goes
out to sea likewise, colouring the water far out, and then subsiding
as a soft tenacious ooze, in which the stones brought out by the ice
are imbedded. And this ooze--so those who have examined it assert--
cannot be distinguished from the brick-clay, or fossiliferous
boulder-clay, so common in the North. A very illustrious
Scandinavian explorer, visiting Edinburgh, declared, as soon as he
saw the sections of boulder-clay exhibited near that city, that this
was the very substance which he saw forming in the Spitzbergen ice-
fiords. {3}
I have put these facts as simply and baldly as I can, in order that
the reader may look steadily at them, without having his attention
drawn off, or his fancy excited, by their real poetry and grandeur.
Indeed, it would have been an impertinence to have done otherwise;
for I have never seen a live glacier, by land or sea, though I have
seen many a dead one. And the public has had the opportunity,
lately, of reading so many delightful books about "peaks, passes, and
glaciers," that I am bound to suppose that many of my readers know as
much, or more, about them than I do.
But let us go a step farther; and, bearing in our minds what live
glaciers are like, let us imagine what a dead glacier would be like;
a glacier, that is, which had melted, and left nothing but its
skeleton of stones and dirt.
We should find the faces of the rock scored and polished, generally
in lines pointing down the valleys, or at least outward from the
centre of the highlands, and polished and scored most in their upland
or weather sides. We should find blocks of rock left behind, and
perched about on other rocks of a different kind. We should find in
the valleys the old moraines left as vast deposits of boulder and
shingle, which would be in time sawn through and sorted over by the
rivers. And if the sea-bottom outside were upheaved, and became dry
land, we should find on it the remains of the mud from under the
glacier, stuck full of stones and boulders iceberg-dropped. This mud
would be often very irregularly bedded; for it would have been
disturbed by the ploughing of the icebergs, and mixed here and there
with dirt which had fallen from them. Moreover, as the sea became
shallower and the mud-beds got awash one after the other, they would
be torn about, re-sifted, and re-shaped by currents and by tides, and
mixed with shore-sand ground out of shingle-beach, thus making
confusion worse confounded. A few shells, of an Arctic or northern
type, would be found in it here and there. Some would have lived
near those later beaches, some in deeper water in the ancient ooze,
wherever the iceberg had left it in peace long enough for sea-animals
to colonise and breed in it. But the general appearance of the dried
sea-bottom would be a dreary and lifeless waste of sands, gravels,
loose boulders, and boulder-bearing clays; and wherever a boss of
bare rock still stood up, it would be found ground down, and probably
polished and scored by the ponderous icebergs which had lumbered over
it in their passage out to sea.
In a word, it would look exactly as vast tracts of the English,
Scotch, and Irish lowlands must have looked before returning
vegetation coated their dreary sands and clays with a layer of brown
vegetable soil.
Thus, and I believe thus only, can we explain the facts connected
with these boulder pebbles. No agent known on earth can have stuck
them in the clay, save ice, which is known to do so still elsewhere.
No known agent can have scratched them as they are scratched, save
ice, which is known to do so still elsewhere.
No known agent--certainly not, in my opinion, the existing rivers--
can have accumulated the vast beds of boulders which lie along the
course of certain northern rivers; notably along the Dee about
Aboyne--save ice bearing them slowly down from the distant summits of
the Grampians.
No known agent, save ice, can have produced those rounded, and
polished, and scored, and fluted rochers moutonnes "sheep-backed
rocks"--so common in the Lake district; so common, too, in Snowdon,
especially between the two lakes of Llanberis; common in Kerry; to be
seen anywhere, as far as I have ascertained, around the Scotch
Highlands, where the turf is cleared away from an unweathered surface
of the rock, in the direction in which a glacier would have pressed
against it had one been there. Where these polishings and scorings
are found in narrow glens, it is, no doubt, an open question whether
some of them may not be the work of water. But nothing but the
action of ice can have produced what I have seen in land-locked and
quiet fords in Kerry--ice-flutings in polished rocks below high-water
mark, so large that I could lie down in one of them. Nothing but the
action of ice could produce what may be seen in any of our mountains-
-whole sheets of rock ground down into rounded flats, irrespective of
the lie of the beds, not in valleys, but on the brows and summits of
mountains, often ending abruptly at the edge of some sudden cliff,
where the true work of water, in the shape of rain and frost, is
actually destroying the previous work of ice, and fulfilling the rule
laid down (I think by Professor Geikie in his delightful book on
Scotch scenery as influenced by its geology), that ice planes down
into flats, while water saws out into crags and gullies; and that the
rain and frost are even now restoring Scotch scenery to something of
that ruggedness and picturesqueness which it must have lost when it
lay, like Greenland, under the indiscriminating grinding of a heavy
sheet of ice.
Lastly; no known agent, save ice, will explain those perched
boulders, composed of ancient hard rocks, which may be seen in so
many parts of these islands and of the Continent. No water power
could have lifted those stones, and tossed them up high and dry on
mountain ridges and promontories, upon rocks of a totally different
kind. Some of my readers surely recollect Wordsworth's noble lines
about these mysterious wanderers, of which he had seen many a one
about his native hills:
As a huge stone is sometimes seen to lie
Couched on the bald top of an eminence,
Wonder to all who do the same espy
By what means it could thither come, and whence;
So that it seems a thing endued with sense:
Like a sea-beast crawled forth, that on a shelf
Of rock or sand reposeth, there to sun itself.
Yes; but the next time you see such a stone, believe that the wonder
has been solved, and found to be, like most wonders in Nature, more
wonderful than we guessed it to be. It is not a sea-beast which has
crawled forth, but an ice-beast which has been left behind; lifted up
thither by the ice, as surely as the famous Pierre-a-bot, forty feet
in diameter, and hundreds of boulders more, almost as large as
cottages, have been carried by ice from the distant Alps right across
the lake of Neufchatel, and stranded on the slopes of the Jura, nine
hundred feet above the lake. {4}
Thus, I think, we have accounted for facts enough to make it probable
that Britain was once covered partly by an ice-sheet, as Greenland is
now, and partly, perhaps, by an icy sea. But, to make assurance more
sure, let us look for new facts, and try whether our ice-dream will
account for them also. Let us investigate our case as a good medical
man does, by "verifying his first induction."
He says: At the first glance, I can see symptoms a, b, c. It is
therefore probable that my patient has got complaint A. But if he
has he ought to have symptom d also. If I find that, my guess will
be yet more probable. He ought also to have symptom e, and so forth;
and as I find successively each of these symptoms which are proper to
A, my first guess will become more and more probable, till it reaches
practical certainty.
Now let us do the same, and say--If this strange dream be true, and
the lowlands of the North were once under an icy sea, ought we not to
find sea-shells in their sands and clays? Not abundantly, of course.
We can understand that the sea-animals would be too rapidly covered
up in mud, and too much disturbed by icebergs and boulders, to be
very abundant. But still, some should surely be found here and
there.
Doubtless; and if my northern-town readers will search the boulder-
clay pits near them, they will most probably find a few shells, if
not in the clay itself, yet in sand-beds mixed with them, and
probably underlying them. And this is a notable fact, that the more
species of shells they find, the more they will find--if they work
out their names from any good book of conchology--of a northern type;
of shells which notoriously, at this day, inhabit the colder seas.
It is impossible for me here to enter at length on a subject on which
a whole literature has been already written. Those who wish to study
it may find all that they need know, and more, in Lyell's "Student's
Elements of Geology," and in chapter xii. of his "Antiquity of Man."
They will find that if the evidence of scientific conchologists be
worth anything, the period can be pointed out in the strata, though
not of course in time, at which these seas began to grow colder, and
southern and Mediterranean shells to disappear, their places being
taken by shells of a temperate, and at last of an Arctic climate;
which last have since retreated either toward their native North, or
into cold water at great depths. From Essex across to Wales, from
Wales to the aestuary of the Clyde, this fact has been verified again
and again. And in the search for these shells, a fresh fact, and a
most startling one, was discovered. They are to be found not only in
the clay of the lowlands, but at considerable heights up the hills,
showing that, at some time or other, these hills have been submerged
beneath the sea.
Let me give one example, which any tourist into Wales may see for
himself. Moel Tryfaen is a mountain over Carnarvon. Now perched on
the side of that mountain, fourteen hundred feet above the present
sea-level, is an ancient sea-beach, five-and-thirty feet thick, lying
on great ice-scratched boulders, which again lie on the mountain
slates. It was discovered by the late Mr. Trimmer, now, alas! lost
to Geology. Out of that beach fifty-seven different species of
shells have been taken; eleven of them are now exclusively Arctic,
and not found in our seas; four of them are still common to the
Arctic seas and to our own; and almost all the rest are northern
shells.
Fourteen hundred feet above the present sea: and that, it must be
understood, is not the greatest height at which such shells may be
found hereafter. For, according to Professor Ramsay, drift of the
same kind as that on Moel Tryfaen is found at a height of two
thousand three hundred feet.
Now I ask my readers to use their common sense over this astounding
fact--which, after all, is only one among hundreds; to let (as Mr.
Matthew Arnold would well say) their "thought play freely" about it;
and consider for themselves what those shells must mean. I say not
may, but must, unless we are to believe in a "Deus quidam deceptor,"
in a God who puts shells upon mountain-sides only to befool honest
human beings, and gives men intellects which are worthless for even
the simplest work. Those shells must mean that that mountain, and
therefore the mountains round it, must have been once fourteen
hundred feet at least lower than they are now. That the sea in which
they were sunk was far colder than now. That icebergs brought and
dropped boulders round their flanks. That upon those boulders a sea-
beach formed, and that dead shells were beaten into it from a sea-
bottom close by. That, and no less, Moel Tryfaen must mean.
But it must mean, also, a length of time which has been well called
"appalling." A length of time sufficient to let the mountain sink
into the sea. Then length of time enough to enable those Arctic
shells to crawl down from the northward, settle, and propagate
themselves generation after generation; then length of time enough to
uplift their dead remains, and the beach, and the boulders, and all
Snowdonia, fourteen hundred feet into the air. And if anyone should
object that the last upheaval may have been effected suddenly by a
few tremendous earthquakes, we must answer--We have no proof of it.
Earthquakes upheave lands now only by slight and intermittent upward
pulses; nay, some lands we know to rise without any earthquake
pulses, but by simple, slow, upward swelling of a few feet in a
century; and we have no reason, and therefore no right, to suppose
that Snowdonia was upheaved by any means or at any rate which we do
not witness now; and therefore we are bound to allow, not only that
there was a past "age of ice," but that that age was one of
altogether enormous duration.
But meanwhile some of you, I presume, will be ready to cry--Stop! It
may be our own weakness; but you are really going on too fast and too
far for our small imaginations. Have you not played with us, as well
as argued with us, till you have inveigled us step by step into a
conclusion which we cannot and will not believe? That all this land
should have been sunk beneath an icy sea? That Britain should have
been as Greenland is now? We can't believe it, and we won't.
If you say so, like stout common-sense Britons, who have a wholesome
dread of being taken in with fine words and wild speculations, I
assure you I shall not laugh at you even in private. On the
contrary, I shall say--what I am sure every scientific man will say--
So much the better. That is the sort of audience which we want, if
we are teaching natural science. We do not want haste, enthusiasm,
gobe-moucherie, as the French call it, which is agape to snap up any
new and vast fancy, just because it is new and vast. We want our
readers to be slow, suspicious, conservative, ready to "gib," as we
say of a horse, and refuse the collar up a steep place, saying--I
must stop and think. I don't like the look of the path ahead of me.
It seems an ugly place to get up. I don't know this road, and I
shall not hurry over it. I must go back a few steps, and make sure.
I must see whether it is the right road; whether there are not other
roads, a dozen of them perhaps, which would do as well and better
than this.
This is the temper which finds out truth, slowly, but once and for
all; and I shall be glad, not sorry, to see it in my readers.
And I am bound to say that it has been by that temper that this
theory has been worked out, and the existence of this past age of
ice, or glacial epoch, has been discovered, through many mistakes,
many corrections, and many changes of opinion about details, for
nearly forty years of hard work, by many men, in many lands.
As a very humble student of this subject, I may say that I have been
looking these facts in the face earnestly enough for more than twenty
years, and that I am about as certain that they can only be explained
by ice, as I am that my having got home by rail can only be explained
by steam.
But I think I know what startles you. It is the being asked to
believe in such an enormous change in climate, and in the height of
the land above the sea. Well--it is very astonishing, appalling--all
but incredible, if we had not the facts to prove it. But of the
facts there can be no doubt. There can be no doubt that the climate
of this northern hemisphere has changed enormously more than once.
There can be no doubt that the distribution of land and water, the
shape and size of its continents and seas, have changed again and
again. There can be no doubt that, for instance, long before the age
of ice, the whole North of Europe was much warmer than it is now.
Take Greenland, for instance. Disco Island lies in Baffin's Bay, off
the west coast of Greenland, in latitude 70 degrees, far within the
Arctic circle. Now there certain strata of rock, older than the ice,
have not been destroyed by the grinding of the ice-cap; and they are
full of fossil plants. But of what kind of plants? Of the same
families as now grow in the warmer parts of the United States. Even
a tulip-tree has been found among them. Now how is this to be
explained?
Either we must say that the climate of Greenland was then so much
warmer than now, that it had summers probably as hot as those of New
York; or we must say that these leaves and stems were floated thither
from the United States. But if we say the latter, we must allow a
change in the shape of the land which is enormous. For nothing now
can float northward from the United States into Baffin's Bay. The
polar current sets OUT of Baffin's Bay southward, bringing icebergs
down, not leaves up, through Davis's Straits. And in any case we
must allow that the hills of Disco Island were then the bottom of a
sea: or how would the leaves have been deposited in them at all?
So much for the change of climate and land which can be proved to
have gone on in Greenland. It has become colder. Why should it not
some day become warmer again?
Now for England. It can be proved, as far as common sense can prove
anything, that England was, before the age of ice, much warmer than
it is now, and grew gradually cooler and cooler, just as, while the
age of ice was dying out, it grew warmer again.
Now what proof is there of that?
This. Underneath London--as, I dare say, many of you know--there
lies four or five hundred feet of clay. But not ice-clay. Anything
but that, as you will see. It belongs to a formation late
(geologically speaking), but somewhat older than those Disco Island
beds.
And what sort of fossils do we find in it?
In the first place, the shells, which are abundant, are tropical--
Nautili, Cones, and such like. And more, fruits and seeds are found
in it, especially at the Isle of Sheppey. And what are they? Fruits
of Nipa palms, a form only found now at river-mouths in Eastern India
and the Indian islands; Anona-seeds; gourd-seeds; Acacia fruits--all
tropical again; and Proteaceous plants too--of an Australian type.
Surely your common sense would hint to you, that this London clay
must be mud laid down off the mouth of a tropical river. But your
common sense would be all but certain of that, when you found, as you
would find, the teeth and bones of crocodiles and turtles, who come
to land, remember, to lay their eggs; the bones, too, of large
mammals, allied to the tapir of India and South America, and the
water-hog of the Cape. If all this does not mean that there was once
a tropic climate and a tropic river running into some sea or other
where London now stands, I must give up common sense and reason as
deceitful and useless faculties; and believe nothing, not even the
evidence of my own senses.
And now, have I, or have I not, fulfilled the promise which I made--
rashly, I dare say some of you thought--in my first paper? Have I,
or have I not, made you prove to yourself, by your own common sense,
that the lowlands of Britain were underneath the sea in the days in
which these pebbles and boulders were laid down over your plains?
Nay, have we not proved more? Have we not found that that old sea
was an icy sea? Have we not wandered on, step by step, into a whole
true fairyland of wonders? to a time when all England, Scotland, and
Ireland were as Greenland is now? when mud streams have rushed down
from under glaciers on to a cold sea-bottom, when "ice, mast high,
came floating by, as green as emerald?" when Snowdon was sunk for at
least fourteen hundred feet of its height? when (as I could prove to
you, had I time) the peaks of the highest Cumberland and Scotch
mountains alone stood out, as islets in a frozen sea?
We want to get an answer to one strange question, and we have found a
group of questions stranger still, and got them answered too. But so
it is always in science. We know not what we shall discover. But
this, at least, we know, that it will be far more wonderful than we
had dreamed. The scientific explorer is always like Saul of old, who
set out simply to find his father's asses, and found them--and a
kingdom besides.
I should have liked to have told you more about this bygone age of
ice. I should have liked to say something to you on the curious
question--which is still an open one--whether there were not two ages
of ice; whether the climate here did not, after perhaps thousands of
years of Arctic cold, soften somewhat for a while--a few thousand
years, perhaps--and then harden again into a second age of ice,
somewhat less severe, probably, than the first. I should have liked
to have hinted at the probable causes of this change--indeed, of the
age of ice altogether--whether it was caused by a change in the
distribution of land and water, or by change in the height and size
of these islands, which made them large enough, and high enough, to
carry a sheet of eternal snow inland; or whether, finally, the age of
ice was caused by an actual change in the position of the whole
planet with regard to its orbit round the sun--shifting at once the
poles and the tropics; a deep question that latter, on which
astronomers, whose business it is, are still at work, and on which,
ere young folk are old, they will have discovered, I expect, some
startling facts. On that last question, I, being no astronomer,
cannot speak. But I should have liked to have said somewhat on
matters on which I have knowledge enough, at least, to teach you how
much there is to be learnt. I should have liked to tell the student
of sea-animals--how the ice-age helps to explain, and is again
explained by, the remarkable discoveries which Dr. Carpenter and Mr.
Wyville Thompson have just made, in the deep-sea dredgings in the
North Atlantic. I should have liked to tell the botanist somewhat of
the pro-glacial flora--the plants which lived here before the ice,
and lasted, some of them at least, through all those ages of fearful
cold, and linger still on the summits of Snowdon, and the highest
peaks of Cumberland and Scotland. I should have liked to have told
the lovers of zoology about the animals which lived before the ice--
of the mammoth, or woolly elephant; the woolly rhinoceros, the cave
lion and bear, the reindeer, the musk oxen, the lemmings and the
marmots which inhabited Britain till the ice drove them out
southward, even into the South of France; and how as the ice
retreated, and the climate became tolerable once more, some of them--
the mammoth and rhinoceros, the bison, the lion, and many another
mighty beast reoccupied our lowlands, at a time when the
hippopotamus, at least in summer, ranged freely from Africa and Spain
across what was then dry land between France and England, and fed by
the side of animals which have long since retreated to Norway and to
Canada. I should have liked to tell the archaeologist of the human
beings--probably from their weapons and their habits--of the same
race as the present Laplanders, who passed northward as the ice went
back, following the wild reindeer herds from the South of France into
our islands, which were no islands then, to be in their turn driven
northward by stronger races from the east and south. But space
presses, and I fear that I have written too much already.
At least, I have turned over for you a few grand and strange pages in
the book of nature, and taught you, I hope, a key by which to
decipher their hieroglyphics. At least, I have, I trust, taught you
to look, as I do, with something of interest, even of awe, upon the
pebbles in the street.