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 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, 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 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.