Glacial Period

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 GreatBritain. 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 winch 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, phœnix-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 zoological 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 palaeontologists 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 ray spare time. Alter a thorough survey of the facts I had collected, he became satisfied that ray interpretation of them was likely to prove correct, and even then be 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 ray 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 bf 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 mountainranges. 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 debris 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 restingplace.

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 Munster. 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 ; 1 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 mountaincolosses 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 sidevalleys 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 front 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,”) thatin 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.2

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 wo 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 Geneva and eastward towards Soleure. 3 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 Phone, occupying the whole space between the Bernese and Valesian Alps, filled to overflowing the valley of the Phone ; 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 Qberland. The glaciers that once filled the valley of Hasli, from the Grimsel to Meyringen, and those that came down from the Wetterhörner, the Schreckhorner, 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 Kamler. 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 Until 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 ns 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 info 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. Hut 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 extrusion 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, imiting 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 debris 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 throughput 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.

  1. It is desirable that the reader should look up these localities upon a map of Switzerland, that he may be impressed with the growing grandeur of these ancient glaciers, even while they were retreating into the heart of the Alps; for in proportion as they left the plain, the landscape must have gained in imposing effect in consequence of the isolation of these immense masses of ice, which in their united extension may have recalled rather the immensity of the ocean, than the grandeur of Alpine scenery.
  2. This map, with all its details and measurements, is reproduced (PI. V. fig. 1) in my “ Système Glaciaire.” It was accompanied by an explanatory paper in the form of a letter to Altmann, then Professor at Herne.
  3. M. de Charpentier has published a map of this ancient glacier in his “ Essay upon the Glaciers and Erratics of the Valley of the