In the early part of the summer of 1840, I started from Switzerland for
England with the express object of finding traces of glaciers in Great
Britain. This glacier-hunt was at that time a somewhat perilous
undertaking for the reputation of a young naturalist like myself, since
some of the greatest names in science were arrayed against the novel
glacial theory. And it was not strange that it should be at first
discredited by the scientific world, for hitherto all the investigations
of geologists had gone to show that a degree of heat far greater than
any now prevailing characterized the earlier periods of the world's
history. Even Charpentier, my precursor and master in glacial research,
who first showed the greater extent of Swiss glaciers in former times,
had not thought of any more general application of his result, or
connected their former boundaries with any great change in the climatic
conditions of the whole continent. His explanation of the phenomena
rested upon the assumption that the Alps formerly rose far beyond their
present height; their greater altitude, he thought, would account for
the existence of immense glaciers extending from the Alps across the
plain of Switzerland to the Jura. Inexperienced as I then was, and
ignorant of the modes by which new views, if founded on truth, commend
themselves gradually to general acceptation, I was often deeply
depressed by the skepticism of men whose scientific position gave them a
right to condemn the views of younger and less experienced students. I
can smile now at the difficulties which then beset my path, but at the
time they seemed serious enough. It is but lately, that, in turning over
the leaves of a journal, published some twelve or fifteen years ago, to
look for a forgotten date, I was amused to find a formal announcement,
under the signature of the greatest geologist of Europe, of the demise
of the glacial theory. Since then it has risen, phoenix-like, from its
own funeral pile.
Even when I arrived in England, many of my friends would fain have
dissuaded me from my expedition, urging me to devote myself to special
zoölogical studies, and not to meddle with general geological problems
of so speculative a character. "Punch" himself did not disdain to give
me a gentle hint as to the folly of my undertaking, terming my journey
into Scotland in search of moraines a sporting-expedition after
"moor-hens." Only one of my older scientific friends in England, a man
who in earlier years had weathered a similar storm himself, shared my
confidence in the investigations looked upon by others as so visionary,
and offered to accompany me in my excursion to the North of England,
Scotland, and Wales. I cannot recur to that delightful journey without a
few words of grateful and affectionate tribute to the friend who
sustained me by his sympathy and guided me by his knowledge and
experience.
For many years I had enjoyed the privilege of personal acquaintance with
Dr. Buckland, and in 1834, when engaged in the investigation of fossil
fishes, I had travelled with him through parts of England and Scotland,
and had derived invaluable assistance from his friendly advice and
direction. To him I was indebted for an introduction to all the
geologists and palæontologists of Great Britain, with none of whom,
except Lyell, had I any previous personal acquaintance; and through him
I obtained not only leave to examine all the fossil fishes in public and
private collections throughout England, but the unprecedented privilege
of bringing them together for closer comparison in the rooms of the
Geological Society of London. A few years later he visited Switzerland,
when I had the pleasure of showing him, in my turn, the glacial
phenomena of my native country, to the study of which I was then
devoting all my spare time. After a thorough survey of the facts I had
collected, he became satisfied that my interpretation of them was likely
to prove correct, and even then he recalled phenomena of his own
country, which, under the new light thrown upon them by the glacial
phenomena of Switzerland, gave a promise of success to my extraordinary
venture. We then resolved to pursue the inquiry together on the occasion
of my next visit to England; and after the meeting in Glasgow of the
British Association for Advancement of Science, we started together for
the mountains of Scotland in search of traces of the glaciers, which, if
there was any truth in the generalizations to which my study of the
Swiss glaciers had led me, must have come down from the Grampian range,
and reached the level of the sea, as they do now in Greenland.
On the fourth of November of that year I read a paper before the
Geological Society of London, containing a summary of the scientific
results of that excursion, which I had extended with the same success to
Ireland and parts of England. This paper was followed by one from Dr.
Buckland himself, containing an account of his own observations, and
another from Lyell on the same subject. From that time, the
investigation of glaciers in regions where they no longer occur has been
carried to almost every part of the globe. Before giving a more special
account of this expedition, I will say a word of the mass of facts which
I had brought from my Alpine researches, on which my own convictions
were founded, and which seemed to Buckland worthy of careful
consideration. To explain these more fully to my readers, I must leave
the Scotch hills for a while, and beg them to return with me to
Switzerland once more.
Thus far I have spoken chiefly of the advance of glaciers, and very
justly, since they are in constant onward motion, being kept within
their limits only by a waste at their lower extremity proportionate to
their advance. But in considering the past history of glaciers, we must
think of their changes as retrograde, not progressive movements; since,
if the glacial theory be true, a great mass of ice, of which the present
glaciers are but the remnants, formerly spread over the whole Northern
hemisphere, and has gradually disappeared, until now no traces of it are
to be found, except in the Arctic regions and in lofty mountain-ranges.
Every terminal moraine, such as I described in the last article, is the
retreating footprint of some glacier, as it slowly yielded its
possession of the plain, and betook itself to the mountains; wherever we
find one of these ancient semicircular walls of unusual size, there we
may be sure the glacier resolutely set its icy foot, disputing the
ground inch by inch, while heat and cold strove for the mastery. There
may have been a succession of cold summers, or, if now and then a warmer
summer intervened, a colder one followed, so that the glacier regained
the next year the ground it had lost during the preceding one, thus
continuing to oscillate for a number of years along the same line, and
adding constantly to the _débris_ collected at its extremity. Wherever
such oscillations and pauses in the retreat of the glacier occurred, all
the materials annually brought down to its terminus were collected; and
when it finally disappeared from that point, it left a wall to mark its
temporary resting-place.
By these semicircular concentric walls we can trace the retreat of the
ice as it withdrew from the plain of Switzerland to the fastnesses of
the Alps. It paused at Berne, and laid the foundation of the present
city, which is built on an ancient moraine; it made a stand again at the
Lake of Thun, and barred its northern outlet by a wall which holds its
waters back to this day. Other moraines, though less distinct, are
visible nearer the base of the Bernese Alps, and, above Meyringen, the
valley is spanned by one of very large dimensions. Again, on the other
side of the first chain of high peaks, the glacier of the Rhone,
descending the valley toward the Lake of Geneva, has everywhere left
traces of its ancient extension. We find the valley crossed at various
distances by concentric moraines, until we reach the lake. There are no
less than thirteen concentric moraines immediately below the present
termination of the glacier of the Rhone, the one nearest to the ice, and
the last formed, marking its present boundary. Others are visible half a
mile, a mile, and two or three miles beyond, near the villages of
Obergestelen and Münster. One of the largest and finest of these ancient
moraines of the glacier of the Rhone stands at Viesch, and extends
across the whole valley, while the Rhone, already swollen by many
mountain-torrents, has cut its way through it. Lower down, we meet with
traces of other ancient glaciers, reaching laterally the main glacier,
which occupied the centre of the valley: such was the glacier of Viesch,
when it extended as far down as the village;[49] such was the glacier of
Aletsch, when it added its burden of ice to that coming from the upper
valley; such was the glacier of the Simplon, whose moraines, of less
antiquity, may now be seen by the road-side leading over the Alps to
Italy; such were the two gigantic twin glaciers that drained the
northern slopes of the mountain-colosses around Monte Rosa and
Matterhorn, united at Stalden, and thence, losing their independence,
became simply lateral tributaries of the great glacier of the Rhone;
such were, farther on, the glaciers coming down from all the
side-valleys opening into the Rhone basin; such were the glaciers of the
St. Bernard, and even those of Chamouni, which in those early days
crossed the Tête Noire to unite below Martigny with those that filled
the valley of the Rhone. Thus the outlines of this glacier may be
followed from its present remnant at the summit of the Valais, where the
Rhone now springs forth from the ice, to the very shores of the Lake of
Geneva, where, near the mouth of the river, on both banks of the valley,
the ancient moraines may be traced to this day, thousands of feet above
the level of the water, marking the course the glacier once followed.
It is evident that here the remains of the glacier mark a process of
retrogression; for had these successive walls of loose materials been
deposited in consequence of the advance of the glacier, they would have
been pushed together in one heap at its lower end. That such would have
been the case is not mere inference, but has been determined by direct
observation in other localities. We know, for instance, by historical
record, (see Gruner's "Natural History of the Glaciers of Switzerland,")
that in the seventeenth century a number of successive moraines existed
at Grindelwald, which have since been driven together by the advance of
the glacier, and now form but one. Indeed, we have ample traditional
evidence of the oscillations of glacier-boundaries in recent times. When
I was engaged in the investigation of this subject, I sought out all the
chronicles kept in old convents or libraries which might throw any light
upon it. Among other records, I chanced upon the following, which may
have some interest for the historian as well as the geologist.
During the religious wars of the sixteenth century, when the Catholics
gained the ascendancy in the Canton of Valais, the inhabitants of the
upper valleys adhered to the Protestant faith. Shut out from ordinary
communication with the Protestant churches by the Bernese Oberland, the
account states that these peasants braved every obstacle to the exercise
of their religion, and used to carry their children over a certain road
by the valley of Viesch, across the Alps, to be baptized at Grindelwald,
on the farther side of the glaciers of Aletsch and Viesch. I could not
understand this statement, for no such road exists, or could be
conceived possible at present; nor was there any knowledge of it among
the guides, intimate as they are with every feature of the region.
Impressed, however, with the idea that there must be some foundation for
the statement, I carefully examined the ground, and, penetrating under
the glacier of Aletsch, I actually found, a number of feet below the
present level of the ice, the paved road along which these hardy people
travelled to church with their children, and some traces of which are
still visible. It has been almost completely buried, although here and
there it reappears; but at this day it is completely impassable for
ordinary travel.
Evidence of a like character is found in a number of facts cited by
Venetz in his celebrated paper upon the variations of temperature in the
Swiss Alps, drawn from the parish and commune registers of the Canton of
Valais. Among these are acts concerning the right to roads which are now
either entirely hidden by ice, or rendered nearly useless by the advance
of the glacier, a lawsuit respecting the use of a forest which no longer
exists, but the site of which is covered by a glacier, and other records
of a similar character. The only document, so far as I know, previous to
this century, which furnishes the means of delineating with any accuracy
the former boundary of a glacier, is a topographical plan of the
environs of the Grimsel, including the extremity of the Aar, making a
part of Altmann's work upon the Alps.
In 1740, Kapeler, a physician of Lucerne, undertook a journey to the
mountains of the Aar, to visit certain crystal grottos, now well known,
but then recently discovered. He prepared a map of these grottos and
their vicinity, in which they are represented as being situated at some
distance from the extremity of the glacier, the lower end of which is
now considerably beyond them.[50]
But to return to the glacier of the Rhone. We can detect the sequence
and relative age of its ancient moraines, not only by their position
with reference to each other and to the present glacier, but also by
their vegetation. The older ones have a mature vegetation; indeed, some
of the largest trees of the valley stand upon the lower moraines, while
those higher up, nearer the glacier, have only comparatively small
trees, and the more recent ones are almost bare of vegetation. Moreover,
we do not lose the track of the great glacier of the Rhone even when we
have followed its ancient boundaries to the shores of the Lake of
Geneva; for along its northern and southern shores we can follow the
lateral moraines marking the limits of the glacier which once occupied
that crescent-shaped depression now filled by the blue waters of the
lake.
M. de Charpentier was the first geologist who attempted to draw the
outlines of the glacier of the Rhone during its greatest extension, when
it not only filled the basin of the Lake of Geneva, but stretched across
the hilly plain to the north, reached the foot of the Jura, and even
rose to a considerable height along the southern slope of that chain of
mountains. At that time the colossal glacier spread at its extremity
like a fan, extending westward in the direction of Geneva and eastward
towards Soleure.[51] The very minute and extensive investigations of
Professor A. Guyot upon the erratic boulders of Switzerland have not
only confirmed the statements of M. de Charpentier, but even shown that
the northeastern boundary of the ancient glacier of the Rhone was more
extensive than was at first supposed. Other researches upon the ancient
moraines along the shores of the Lake of Geneva, and in other parts of
Switzerland, in which most geologists of the day took an active part,
have made us as fully conversant with the successive outlines and
varying extent of the principal glaciers ranging from the Alpine summits
to the surrounding lowlands as we are with the glaciers in their present
circumscription. But no one has done as much as Professor Guyot to add
precision to these investigations. The number of localities, the level
of which he has determined barometrically, with the view of fixing the
ancient levels of all these vanished glaciers, is almost incredible. The
result of all these surveys has been a distinct recognition of not less
than seven gigantic glaciers descending from the northern and western
slopes of the Alps to the adjoining hilly plains of Switzerland and
France. It is most interesting to trace their outlines upon a recent map
of those countries, but it requires that kind of intellectual effort of
the imagination without which the most brilliant results of modern
science remain an unmeaning record to us. Let us, nevertheless, try to
follow.
The glacier of the Rhone, occupying the whole space between the Bernese
and Valesian Alps, filled to overflowing the valley of the Rhone; at
Martigny it was met by a large tributary from Mont Blanc, by the side of
which it advanced into the plain beyond, filling the whole Lake of
Geneva, and covering the beautiful Canton de Vaud and parts of Fribourg,
Neuchâtel, Berne, and Soleure, rising to the crest of the Jura, and in
many points penetrating even beyond its outer range.
To the east of this, the largest of all the ancient glaciers of
Switzerland, we find the ancient glacier of the Aar, descending from the
northern slope of the whole range of the Bernese Oberland. The glaciers
that once filled the valley of Hasli, from the Grimsel to Meyringen, and
those that came down from the Wetterhörner, the Schreckhörner, the
Finster-Aarhorn, and the Jungfrau, through the valleys of Grindelwald
and Lauterbrunnen, united in a common bed, the bottom of which was the
present basin of the Lakes of Brientz and Thun. These were joined by the
glaciers emptying their burden through the valley of the Kander. To
these combined glaciers the formation of the terminal moraine of Thun
must be ascribed. But before this had been formed, the glacier of the
Aar, in its amplest extension, had also reached the foot of the Jura,
without, however, spreading so widely as the glacier of the Rhone.
Farther to the east Professor Guyot has traced the boundaries of three
other colossal glaciers, one of which derived its chief supplies from
the Alps of Uri, bringing with it all the tributaries which the main
glacier coming down from the St. Gothard received right and left, in its
course through the valley of the Reuss and the basins of the Lakes of
Lucerne and Zug. The second, born in the Canton of Glaris, followed
mainly the present course of the Linth and the basin of the Lake of
Zurich. Professor Escher von der Linth has shown that the lovely city of
Zurich is built upon a moraine, like Berne. The imagination shrinks from
the thought that all the beautiful scenery of those countries should
once have been hidden under masses of ice, like those now covering
Greenland. The easternmost ancient glacier of Switzerland is that of the
Rhine, arising from all the valleys from which now descend the many
tributaries of that stream, spreading over the northeastern Cantons,
filling the Lake of Constance, and terminating at the foot of the
Suabian Alp. Next to the glacier of the Rhone, this was once the largest
of those descending from the range of the Alps.
West of Mont Blanc Professor Guyot has traced the boundaries of two
other distinct ancient glaciers; one of which, the glacier of the Arve,
followed chiefly the course of the Arve, and, though discharging the icy
accumulations from the western slope of Mont Blanc, was, as it were,
only a lateral affluent of the great glacier of the Rhone. The other,
the glacier of the Isère, occupied, to the south and west of the
preceding, the large triangular space intervening between the Alps and
the Jura, in that part of Savoy where the two mountain-chains converge
and become united.
It would lead me too far, were I to describe also the course of the
great ancient glaciers which descended from the southern slopes of the
Alps into the plain of Northern Italy. Moreover, these boundaries are
not yet ascertained with the same degree of accuracy as those of the
northern and western slopes; though very accurate descriptions of some
of them have been published, with illustrations on a large scale, by MM.
Martins and Gastaldi, and of others by Professor Ramsey. I have myself
examined only the upper part of that of the valley of Aosta.
The evidence concerning the ancient glaciers of the Alps, especially
within the limits of Switzerland, is already so full that it affords
ample means for a comprehensive general view of the subject. It is
frequently the case, that, when a stretch of time or space lies between
us and a matter we have once studied more closely, it presents itself to
us as a whole more vividly than when our nearness to it forced all its
details upon our observation. In my present position, now that the lapse
of many years separates me from my personal investigations of the
ancient and modern glaciers, and I look back upon them from another
continent, it seems to me that I have, as it were, a bird's-eye view of
their whole extent; and I confess that this distant retrospect of the
subject has been to me almost as fascinating as were the researches of
my earlier years in the same direction. I wish that I could present it
to the minds of my readers with something of the attraction it possesses
for me. I trust, however, that I have made it plain to them that the
great mountain-chain of the Alps has been a central axis from which
immense glaciers at one time descended in every direction, not only to
its base, beyond which the lowlands extend in flat undulations, but to a
greater or less distance over the adjoining plains; while at present
they are confined to the higher valleys. So far, then, notwithstanding
the extraordinary difference in their dimensions, at the time they
reached the Jura and the plain of Northern Italy, when compared with
what they are now, they seem directly connected with the Alps, and the
mountains appear as their birthplace; so much so that the first attempts
at a generalization concerning their origin started from the assumption
that they must have been formed between the high ridges from which they
seem to flow down. These facts, then the only ones known concerning a
greater extension of the glaciers, naturally led to the views advocated
by M. de Charpentier. My own theory was also at first, that the upheaval
of the Alps must, in some way or other, have been connected with these
phenomena. But it soon became evident to me that these views were
inadequate to account for the former presence of extensive glaciers in
other parts of Europe; and even within the range of the Alps there were
insuperable objections to their final admission. If the ancient glaciers
had been first formed among the highest mountains, and extended
downwards into the plains, the largest and highest moraines ought to be
the most distant, and to be formed of the most rounded masses; whereas
the actual condition of the detrital accumulations is the reverse, the
distant materials being widely spread, and true moraines being found
only in valleys connected with great chains of lofty mountains.
Again, all these moraines are within one another,--the most distant from
the glacier to which they owe their origin encircling all those which
are nearer and nearer to it within the same glacial basin. And as no
glacier could reach to its farthest moraine without pushing forward all
the intervening loose materials, it is self-evident that the outer
moraines were first formed, and those nearer the glacier subsequently,
in the order in which they follow one another from the lower valleys to
the higher levels at which alone glaciers exist at present. Translating
these facts into words, we see that the glaciers to which these ancient
moraines owe their origin must have been retreating gradually while the
moraines were accumulating. But a glacier while uniformly retreating
forms no high walls of loose materials around its edges and at its lower
extremity; as it melts away, it only drops the burden of angular rocky
fragments which it carries upon its back over the loose fragments above
which it moves, and which it grinds to powder, or to sand, or to rounded
pebbles, in its progress. It is only where the glacier remains
stationary for a longer or shorter period that large terminal moraines
can accumulate; and they are generally found in such places in the
valleys of the Alps as would naturally determine the lower limit of a
glacier for the time being. There is no possibility of escaping the
conclusion that the ancient glaciers must have begun that series of
oscillations to which the accumulation of the moraines is to be
ascribed, at a time when ice-fields already occupied the whole area
which they have covered during their greatest extension. After we shall
have seen how many centres of dispersion of erratic boulders existed in
the northern hemisphere, similar to that of the Alps, we may perhaps be
able to form some idea of the manner in which these ice-fields
originated and gradually vanished.
Some investigators have been inclined to explain the presence of
boulders, moraines, drift, and the like phenomena, by the action of
water. But even if we could believe that rivers had brought along with
them such masses of rock, and deposited them where they are now found,
the regularity in the distribution of the materials disproves any such
theory. In the lateral moraines of the Lake of Geneva we have a striking
illustration of this apparently systematic division of the loose
materials; for the northeastern moraines of that glacial basin contain
rocks belonging exclusively to the northern side of the valley of the
Rhone, while the moraines on the southern shore of the lake consist of
rocks belonging to its southern side. Indeed, rivers, so far from
building up moraines, have often partially destroyed them. We find
various instances of moraines through which a river runs, having worn
for itself a passage, on either side of which the form of the moraine
remains unbroken. In the valley of the Rhone there are villages built on
such moraines, as, for instance, Viesch, with the river running through
their centre.
But if we need further confirmation of the fact that these accumulations
on either side of this and other Swiss lakes are ancient lateral
moraines, we have it in their connection with walls of a like nature at
their lower end, where we find again transverse moraines barring their
outlet, and also in the continuity of long trains of fragments of
similar rocks extending side by side across wide plains for great
distances without mixture. From the beginning of my investigations upon
the glaciers, I have urged these two points as most directly proving
their greater extension in former times, and more recent researches
constantly recur to this kind of evidence. All our lakes would be filled
with loose materials, had their basins not been sheltered by ice against
the encroachments of river-deposits during the transportation of the
erratic boulders to the farthest limits of their respective areas; and
all the continuous trails of rocks derived from the same locality would
have been scattered over wide areas, had they not been carried along, in
unyielding tracks, like moraines. On a small scale the waters of the
Rhone and of the Arve recall to this day such a picture. There are few
travellers in Switzerland who have not seen these two rivers, where they
flow side by side, meeting, but not mingling, at the southern extremity
of the lake, the different color of their water marking the two parallel
currents. In old times, when the glaciers filled all the valleys at the
base of Mont Blanc, and to the east of it, uniting in the valley through
which now runs the River Rhone, the glacier of the Arve came down to
meet the ice from the valley of the Rhone, in the same manner as the
River Arve now comes to meet the waters of the Rhone where they rush out
from the southern end of the lake.
This would be the proper place to consider the formation of the lakes of
Switzerland, as well as their preservation by the agency of glaciers.
But this subject is so intricate, and has already given rise to so many
controversies which could not be overlooked in this connection, that I
prefer to pass it over altogether in silence. Suffice it to say that not
only are most of the lakes of Switzerland hemmed in by transverse
moraines at their lower extremity, but the lakes of Upper Italy, at the
foot of the Alps, are barred in the same way, as are also the lakes of
Norway and Sweden, and some of our own ponds and lakes. Strange as it
may seem to the traveller who sails under an Italian sky over the lovely
waters of Como, Maggiore, and Lugano, it is, nevertheless, true, that
these depressions were once filled by solid masses of ice, and that the
walls built by the old glaciers still block their southern outlets.
Indeed, were it not for these moraines, there would be comparatively few
lakes either in Northern Italy or in Switzerland. The greater part of
them have such a wall built across one end; and but for this masonry of
the glacier, there would have been nothing to prevent their waters from
flowing out into the plain at the breaking up of the ice-period. We
should then have had open valleys in place of all these sheets of water
which give such diversity and beauty to the scenery of Northern Italy
and Switzerland, or, at least, the lakes would be much fewer and occupy
only the deeper depressions in the hard rocks.
Such being the evidences of the former extent of the glaciers in the
plains, what do the mountain-summits tell us of their height and depth?
for here, also, they have left their handwriting on the wall. Every
mountain-side in the Alps is inscribed with these ancient characters,
recording the level of the ice in past times. Here and there a ledge or
terrace on the wall of the valley has afforded support for the lateral
moraines, and wherever such an accumulation is left, it marks the limit
of the ice at some former period. These indications are, however,
uncertain and fragmentary, depending upon projections of the rocky
walls. But thousands of feet above the present level of the glacier, far
up toward their summits, we find the sides of the mountains furrowed,
scratched, and polished in exactly the same manner as the surfaces over
which the glaciers pass at present. These marks are as legible and clear
to one who is familiar with glacial traces as are hieroglyphics to the
Egyptian scholar; indeed, more so,--for he not only recognizes their
presence, but reads their meaning at a glance. Above the line at which
these indications cease, the edges of the rocks are sharp and angular,
the surface of the mountain rough, unpolished, and absolutely devoid of
all those marks resulting from glacial action. On the Alps these traces
are visible to a height of nine thousand feet, and across the whole
plain of Switzerland, as I have stated, one may trace the glaciers by
their moraines, by the masses of rock they have let fall here and there,
by the drift they have deposited, to the very foot of the opposite
chain, where they have dropped their boulders along the base of the
Jura. Ascending that chain, one finds the grooved, polished, and
scratched surfaces to its summit, on the very crest of which boulders
entirely foreign to the locality are perched. Follow the range down upon
the other side and you find the same indications extending into the
plains of Burgundy and France beyond.
With a chain of evidence so complete, it seems to me impossible to deny
that the whole space between the opposite chains of the Alps and the
Jura was once filled with ice; that this mass of ice completely covered
the Jura, with the exception of a few high crests, perhaps, rising
island-like above it, and mounted to a height of some nine thousand feet
upon the Alps, while it extended on the one side into the northern plain
of Italy, filling all its depressions, and on the other down to the
plains of Central Europe. The only natural inference from these facts
is, that the climatic conditions leading to their existence could not
have been local; they must have been cosmic. When Switzerland was
bridged across from range to range by a mass of ice stretching southward
into Lombardy and Tuscany, northward into France and Burgundy, the rest
of Europe could not have remained unaffected by the causes which induced
this state of things.
It was this conviction which led me to seek for the traces of glaciers
in Great Britain. I had never been in the regions I intended to visit,
but I knew the forms of the valleys in the lake-country of England, in
the Highlands of Scotland, and in the mountains of Wales and Ireland,
and I was as confident that I should find them crossed by terminal
moraines and bordered by lateral ones, as if I had already seen them.
The reader must not suppose, when I describe these walls, formed of the
_débris_ of the glacier, as consisting of boulders, stones, pebbles,
sand, and gravel, a rough accumulation of loose materials
indiscriminately thrown together, that we find the ancient moraines
presenting any such appearance. Time, which mellows and softens all the
wrecks of the past, has clothed them with turf, grassed them over,
planted them with trees, sown his seed and gathered in his harvests upon
them, until at last they make a part of the undulating surface of the
country. Were it not for anticipating my story, I could point out many a
green billow, rising out of the fields and meadows immediately about us,
that had its origin in the old ice-time. Thus disguised, they are not so
evident to the casual observer; but, nevertheless, when once familiar
with the peculiar form, character, and position of these rounded ridges
scattered over the face of the country, they are easily recognized.
Of course, the ancient glaciers of Great Britain were far more difficult
to trace than those of Switzerland, where the present glaciers are
guides to the old ones. But, nevertheless, my expectations were more
than answered. The first valley I entered in the glacial regions of
Scotland was barred by a terminal moraine; and throughout the North of
England, as well as in Scotland and Ireland, I found the hill-sides
covered with traces of glacial action, as distinct and unmistakable as
those I had left in my native land. And not only was the surface of the
country polished, grooved, and scratched, as in the region of existing
glaciers, and presenting an appearance corresponding exactly to that
described elsewhere, but we could track the path of the boulders where
they had come down from the hills above and been carried from the mouth
of each valley far down into the plains below. In Scotland and Ireland
the phenomena were especially interesting. I had intended to give in
this article some account of the "parallel roads" of Glenroy, marking
the ancient levels of glacier-lakes, so much discussed in this
connection. But the reminiscences of old friends, and the many
associations revived in my mind by recurring to a subject which I have
long looked upon as a closed chapter, so far as my own researches are
concerned, have constantly led me beyond the limits I had prescribed to
myself in these papers upon glaciers; and as the story of Glenroy and
the phenomena connected with it is a long one, I shall reserve it for a
subsequent number.
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