It is a more shameful illustration of the same weakness, when the pens of literary men, not dependent on local support, are subsidized by the prejudice or sold to the pride and wealth of the society in which they live. "I believe in testifying," once said a great man; and we have, among the philosophic and learned, noble witnesses for the equity of our national case. But what a spectacle of degraded functions, when poets, historians, and religious thinkers bow the knee to an aristocracy so vilely proud to stretch forth its hand of fellowship to a slaveholding brotherhood beyond the sea! We need not denounce them. The ideas they pretend to stand for hold them in scorn. The imagination whose pictures they drew will quench all her lustre for the deserters that devote themselves to the slavish passions of the hour. The history whose tales of glory and ignominy they related will rear a gibbet for their own reputation in the future time. As for us, at the present, we mention not their names, but, like the injured ghost in the poet's picture of the world of spirits, turn from them silently and pass on. We remember there was a grand old republican in the realm of letters, John Milton by name, whose shade must be terrible to their thoughts. Let them beware of making of themselves a public shame. The great revenge of years will turn into a mere trick of literature the prose and verse of all not inspired by devotion to humanity, zeal for the cause of the oppressed, and a hearty love of truth, while every covering of lies shall be torn away. They who have despised our free institutions, and prophesied our downfall, and gloated by anticipation over the destruction of our country, to get the lease of a hundred years more to their own lordship of Church and State, and have put their faith in the oppressive Rebels trying to build an empire on the ruins of the Ten Commandments, are as blind to discern the laws of human nature as they are awkward to raise the horoscope of events. This Western Continent, under God, may it please the despots, is not going to barbarism and desolation. That good missionary of freedom as well as religion, whom New England sent to California in the person of Thomas Starr King, writes us that Mount Shasta is ascertained to be higher than Mont Blanc. Some other elevations than of the surface of the globe, in this hemisphere, the Transatlantics may yet behold.

The pulpit is but a sympathetic deceiver, when it violates the truth it is set to defend. All its lies are echoes of the avarice and inhumanity sitting in the pews; and when, in the rough old figure, it is a dumb dog that will not bark at the robber or warn us of danger, the real mutes, whom its silence but copies, are those demure men below who seem to listen to its instructions.

We are astonished to find a liar in the lightning of heaven over the telegraphic wires. Let us get over our surprise. The lie is human altogether, not elemental at all. The operator has his private object to carry, the partisan his political end to serve, the government itself flatters the people it fears with incorrect accounts of military movements and fortified posts and the numbers of dead and wounded on either side. Kinglake calls the telegraph a device by which a clerk dictates to a nation. Who but the nation, or some part of it, dictates to the clerk? He does not control, but records, the sentiment of the community in all his invented facts; and when we hear the click or read the strange dots, we want some trustworthy voucher or responsible human auditor even of these electric accounts.

"As the minister began on the subject of Slavery, I left the church," said a respectable citizen to a modest woman, of whose consent with him he felt sure.

"And did the minister go on?" she gently inquired.

"Yes, he went on," the mistaken citizen replied.

So, in this land, let us go on in the way of justice and truth we have at last begun. Let us have no more sympathetic, however once legal, lies for oppression and wrong. We shall be as good as a thousand years old, when we are through our struggle. For the respect of Europe let us have no anxiety. It will come cordially or by constraint, upon the victory of the right and the reinstating of our manhood by the divine law, to the discouragement of all iniquity at home or abroad. Our success will be a signal for all the tyrannies, in which the proud and strong have been falsely banded together to crush the ignorant and lowly, to come down. The domineering political and ecclesiastical usurpers of exclusive privilege will no longer give and take reciprocal support against the rising of mankind than the Roman augurs could at last keep one another in countenance. Let us go on, through dark omens as well as bright, and suffer ourselves to have no doubting day. Let us show that something besides a monarchy in this world can stand. On disbelievers and obstructers let us have companion. They cannot live contented, and it is not quite safe for them to die. The path of our progress opens clear. Let us not admit the idea of failure. To think of failing is to fail. As it was with the sick before their Saviour of old, only our faith can make us whole.

Instinctively, Treason, in this vast land, aimed its first blow at the Genius of Communication,—the benign and potent means and method of American civilization and nationality. The great problem Watt and Fulton, Clinton and Morse so gloriously solved, a barbaric necessity thus reduces back to chaos; and not the least sad and significant of the bulletins whereby the most base of civic mutinies finds current record is that entitled, "Destruction of the Bridges"; and (melancholy contrast!) simultaneously we hear of constructive energy in the same direction, on the Italian peninsula,—an engineer having submitted to Victor Emmanuel proposals for throwing a bridge across the Straits of Messina, "binding Scylla to Charybdis, and thus clinching Italian unity with bonds of iron." Bonds of nationality, in more than a physical sense, indeed, are bridges: even cynical Heine found an endeared outlook to his native Rhine on the bastion of a familiar bridge; Tennyson makes one an essential feature of his English summer picture, wherein forever glows the sweet image of the "Gardener's Daughter"; and Bunyan found no better similitude for Christian's passage from Time to Eternity than the "river where there is no bridge."

A bridge of the simplest kind is often charmingly effective as a landscape-accessory: there is a short plank one in a glen of the White Mountains, which, seen through a vista of woodland, makes out the picture so aptly that it is sketched by every artist who haunts the region. What lines of grace are added to the night view of a great city by the lights on the bridges! what subtile principles enter into the building of such a bridge as the Britannia, where even the metallic contraction of the enormous tubes is provided for by supporting them on cannon-balls! how venerable seems the most graceful of Tuscan bridges, when we remember it was erected in the fifteenth century,—and the Rialto, when we think that it was designed by Michel Angelo! and how signal an instance is it of the progressive application of a true principle in science, that the contrivance whereby the South-Americans bridge the gorges of their mountains, by a pendulous causeway of twisted osiers and bamboo,—one of which, crossed by Humboldt, was a hundred and twenty feet long,—is identical with that which sustains the magnificent structure over the Niagara River! In a bridge the arch is triumphal, both for practical and commemorative ends: unknown to the Greeks and Egyptians, even the ancient Romans, it is said by modern architects, did not appreciate its true mechanical principle, but ascribed the marvellous strength thereof to the cement which kept intact their semicircle. In Cæsar's "Commentaries," the bridge transit and vigilance form no small part of military tactics,—boats and baskets serving the same purpose in ancient and modern warfare. The Church of old originated and consecrated bridges; religion, royalty, and art celebrate their advent; the opening of Waterloo Bridge is the subject of one of the best pictures of a modern English painter; and Cockney visitors to the peerless Bridge of Telford still ask the guide where the Queen stood at its inauguration. But it is when we turn from the historical and scientific to the familiar and personal that we realize the spontaneous interest attached to a bridge. It is as a feature of our native landscape, the goal of habitual excursions, the rendezvous, the observatory, the favorite haunt or transit, that it wins the gaze and the heart. There the musing angler sits content; there the echoes of the horse's hoofs rouse to expectancy the dozing traveller; there the glad lover dreams, and the despairing wretch seeks a watery grave, and the song of the poet finds a response in the universal heart,—

The bridge is, accordingly, of all economical inventions, that which is most inevitable to humanity, signalizing the first steps of man amid the solitude of Nature, and accompanying his progress through every stage of civic life: its crude form makes the wanderer's heart beat in the lonely forest, as a sign of the vicinity or the track of his kind; and its massive remains excite the reverent curiosity of the archæologist, who seeks among the ruins of Art for trophies of a by-gone race. Few indications of Roman supremacy are more striking than the unexpected sight of one of those bridges of solid and symmetrical masonry which the traveller in Italy encounters, when emerging from a mountain-pass or a squalid town upon the ancient highway. The permanent method herein apparent suggests an energetic and pervasive race whose constructive instinct was imperial; such an evidence of their pathway over water is as suggestive of national power as the evanescent trail of the savage is of his casual domain. In the bridge, as in no other structure, use combines with beauty by an instinctive law; and the stone arch, more or less elaborate in detail, is as essential now to the function and the grace of a bridge as when it was first thrown, invincible and harmonious, athwart the rivers Cæsar's legions crossed.

As I stood on the scattered planks which afford a precarious foothold amid the rapids of St. Anthony, methought these frail bridges of hewn timber accorded with the reminiscence of the missionary pioneer who discovered and named the picturesque waters more than an elaborate and ancient causeway. Even those long, inelegant structures which lead the pedestrian over our own Charles River, or the broad inlets of the adjacent bay, have their peculiar charm as the scene of many a gorgeous autumnal sunset and many a patient "constitutional" walk. It is a homely, but significant proverb, "Never find fault with the bridge that carries you safe over." What beautiful shadows graceful bridges cast, when the twilight deepens and the waves are calm! how mysteriously sleep the moonbeams there! what a suggestive vocation is a toll-keeper's' patriarchs in this calling will tell of methodical and eccentric characters known for years.

How isolated and bewildered are villagers, when, after a tempest, the news spreads that a freshet has carried away the bridge! Every time we shake hands, we make a human bridge of courtesy or love; and that was a graceful fancy of one of our ingenious writers to give expression to his thoughts in "Letters from under a Bridge." With an eye and an ear for Nature's poetry, the gleam of lamps from a bridge, the figures that pass and repass thereon, the rush and the lull of waters beneath, the perspective of the arch, the weather-stains on the parapet, the sunshine and the cloud-shadows around, are phases and sounds fraught with meaning and mystery.

When we look forth upon a grand or lovely scene of Nature,—mountain, river, meadow, and forest,—what a fine central object, what an harmonious artificial feature of the picture, is a bridge, whether rustic and simple, a mere rude passage-way over a brook, or a curve of gray stone throwing broad shadows upon the bright surface of a river! Nor less effective is the same object amid the crowded walls, spires, streets, and chimney-stacks of a city. There the bridge is the least conventional structure, the suggestive point, the favorite locality; it seems to reunite the working-day world with the freedom of Nature; it is perhaps the one spot in the dense array of edifices and thoroughfares which "gives us pause." There, if anywhere, our gaze and our feet linger; people have a relief against the sky, as they pass over it; artists look patiently thither; lovers, the sad, the humorous, and the meditative, stop there to observe and to muse; they lean over the parapet and watch the flowing tide; they look thence around as from a pleasant vantage-ground. The bridge, in populous old towns, is the rendezvous, the familiar landmark, the traditional nucleus of the place, and perhaps the only picturesque framework in all those marts and homes, more free, open, and suggestive of a common lot than temple, square, or palace; for there pass and repass noble and peasant, regal equipage and humble caravan; children plead to stay, and veterans moralize there; the privileged beggar finds a standing-place for charity to bless; a shrine hallows or a sentry guards, history consecrates or Art glorifies, and trade, pleasure, or battle, perchance, lends to it the spell of fame. Let any one recall his sojourn in a foreign city, and conjure to his mind's eye the scenes, and prominent to his fancy, distinct to his memory, will be the bridge. He will think of Florence as intersected by the Arno, and with the very name of that river reappears the peerless grace of the Ponte Santa Trinità with its moss-grown escutcheons and aërial curves; the Pont Neuf, at Paris, with its soldiers and priests, its boot-blacks and grisettes, the gay streets on one side and the studious quarter on the other, typifies and concentrates for him the associations of the French capital; and what a complete symbol of Venice—its canals, its marbles, its mysterious polity, its romance of glory and woe—is a good photograph of the Bridge of Sighs!

The history of Rome is written on her bridges. The Ponte Rotto is Art's favorite trophy of her decay; two-thirds of it has disappeared; and the last Pope has ineffectively repaired it, by a platform sustained by iron wire: yet who that has stood thereon in the sunset, and looked from the dome of St. Peter's to the islands projected at that hour so distinctly from the river's surface, glanced along the flushed dwellings upon its bank, with their intervals of green terraces, or gazed, in the other direction, upon the Cloaca of Tarquin, Vesta's dome, and the Aventine Hill, with its palaces, convents, vineyards, and gardens, has not felt that the Ponte Rotto was the most suggestive servatory in the Eternal City? The Ponte Molle brings back Constantine and his vision of the Cross; and the statues on Sant' Angelo mutely attest the vicissitudes of ecclesiastical eras.

But the economical and the artistic interest of bridges is often surpassed by their historical suggestions; almost every vocation and sentiment of humanity being intimately associated therewith. The Rialto at Venice and the Ponte Vecchio at Florence are identified with the financial enterprise of the one city and the goldsmith's skill of the other: one was long the Exchange of the "City of the Sea," and still revives the image of Shylock and the rendezvous of Antonio; while the other continues to represent mediæval trade in the quaint little shops of jewellers and lapidaries. One of the characteristic religious orders of that era is identified with the ancient bridge which crosses the Rhone at Avignon, erected by the "Brethren of the Bridge," a fraternity instituted in an age of anarchy expressly to protect travellers from the bandits, whose favorite place of attack was at the passage of rivers. The builder of the old London Bridge, Peter Colechurch, is believed to have been attached to this same order; he died in 1176, and was buried in a crypt of the little chapel on the second pier, according to the habit of the fraternity. For many years a market was held on this bridge; it was often the scene of war; it stayed the progress of Canute's fleet; at one time destroyed by fire, and at another carried away by ice; half ruined in one era by the bastard Faulconbridge, and, at another, the watchword of civil war, when the cry resounded, "Cade hath gotten Londonbridge," and Wat Tyler's rebels convened there; Elizabeth and her peerless courtiers have floated, in luxurious barges and splendid attire, by its old piers, and the heads of traitors rotted in the sun upon its venerable battlements. Only sixty years ago a portion of the original structure remained; it was once covered with houses; Peter the Dutchman's famous water-wheels plashed at its side; from the dark street and projecting gables noted tavern-signs vibrated in the wind. The exclusive thoroughfare from the city to Kent and Surrey, what ceremonial and scenes has it not witnessed,—royal entrances and greetings, rites under the low brown arches of the old chapel, revelry in the convenient hostels, traffic in the crowded mart, chimes from the quaint belfry, the tragic triumph of vindictive law in the gory heads upon spikes! The veritable and minute history of London Bridge would illustrate the civic and social annals of England; and romance could scarce invent a more effective background for the varied scenes and personages such a chronicle would exhibit than the dim local perspective, when, ere any bridge stood there, the ferryman's daughter founded with the tolls a House of Sisters, subsequently transformed into a college of priests. By a law of Nature, thus do the elements of civilization cluster around the place of transit; thus do the courses of the water indicate the direction and nucleus of emigration,—from the vast lakes and mighty rivers of America, whereby an immense continent is made available to human intercourse, and therefore to material unity, to the point where the Thames was earliest crossed and spanned. More special historical and social facts may be found attached to every old bridge. In war, especially, heroic achievement and desperate valor have often consecrated these narrow defiles and exclusive means of advance and retreat:—

The bridge of Darius spanned the Bosphorus,—of Xerxes, the Hellespont,—of Cæsar, the Rhine,—and of Trajan, the Danube; while the victorious march of Napoleon has left few traces so unexceptionably memorable as the massive causeways of the Simplon. Cicero arrested the bearer of letters to Catiline on the Pons Milonis, built in the time of Sylla on the ancient Via Flaminia; and by virtue of the blazing cross which he saw in the sky from the Ponte Molle the Christian emperor Constantine conquered Maxentius. The Pont du Gard near Nismes and the St. Esprit near Lyons were originally of Roman construction. During the war of freedom, so admirably described by our countryman, whereby rose the Dutch Republic, the Huguenots, at the siege of Valenciennes, we are told, "made forays upon the monasteries for the purpose of procuring supplies, and the broken statues of the dismantled churches were used to build a bridge across an arm of the river, which was called, in derision, the Bridge of Idols."

Amid the mass of prosaic structures in London, what a grand exception to the architectural monotony are her bridges! how effectually they have promoted her suburban growth! Canova thought the Waterloo Bridge the finest in Europe, and, by a strangely tragic coincidence, this noble and costly structure is the favorite scene of suicidal despair, wherewith the catastrophes of modern novels and the most pathetic of city lyrics are indissolably associated. Westminster Bridge is as truly the Swiss Laboyle's monument of architectural genius, fortitude, and patience, as St. Paul's is that of Wren; and our own Remington's bridge-enthusiasm involves a pathetic story. At Cordova, the bridge over the Guadalquivir is a grand relic of Moorish supremacy. The oldest bridge in England is that of Croyland in Lincolnshire; the largest crosses the Trent in Staffordshire. Tom Paine designed a cast-iron bridge, but the speculation failed, and the materials were subsequently used in the beautiful bridge over the River Wear in Durham County. There is a segment of a circle six hundred feet in diameter in Palmer's bridge which spans our own Piscataqua. It is said that the first edifice of the kind which the Romans built of stone was the Ponte Rotto, begun by the Censor Fulvius and finished by Scipio Africanus and Lucius Mummius. Popes Julius III. and Gregory XIV. repaired it; so that the fragment now so valued as a picturesque ruin symbolizes both Imperial and Ecclesiastical rule. In striking contrast with the reminiscences of valor, hinted by ancient Roman bridges, are the ostentatious Papal inscriptions which everywhere in the States of the Church, in elaborate Latin, announce that this Pontiff built or that Pontiff repaired these structures.

The mediæval castle moat and drawbridge have, indeed, been transferred from the actual world to that of fiction, history, and art, except where preserved as memorials of antiquity; but the civil importance which from the dawn of civilization attached to the bridge is as patent to-day as when a Roman emperor, a feudal lord, or a monastic procession went forth to celebrate or consecrate its advent or completion; in evidence whereof, we have the appropriate function which made permanently memorable the late visit of Victoria's son to her American realms, in his inauguration of the magnificent bridge bearing her name, which is thrown across the St. Lawrence for a distance of only sixty yards less than two English miles,—the greatest tubular bridge in the world. When Prince Albert, amid the cheers of a multitude and the grand cadence of the national anthem, finished the Victoria Bridge by giving three blows with a mallet to the last rivet in the central tube, he celebrated one of the oldest, though vastly advanced, triumphs of the arts of peace, which ally the rights of the people and the good of human society to the representatives of law and polity.

Fragments, as well as entire roadways and arches of natural bridges, are more numerous in rocky, mountainous, and volcanic regions than is generally supposed; the action of the water in excavating cliffs, the segments of caverns, the, accidental shapes of geological formations, often result in structures so adapted for the use and like the shape of bridges as to appear of artificial origin. In the States of Alabama and Kentucky, especially, we have notable instances of these remarkable freaks of Nature: there is one in Walker County, of the former State, which, as a local curiosity, is unsurpassed; and one in the romantic County of Christian, in the latter State, makes a span of seventy feet with an altitude of thirty; while the vicinity of the famous Alabaster Mountain of Arkansas boasts a very curious and interesting formation of this species. Two of these natural bridges are of such vast proportions and symmetrical structure that they rank among the wonders of the world, and have long been the goals of pilgrimage, the shrines of travel. Their structure would hint the requisites, and their forms the lines of beauty, desirable in architectural prototypes. Across Cedar Creek, in Rockbridge County, Virginia, a beautiful and gigantic arch, thrown by elemental forces and shaped by time, extends. It is a stratified arch, whence you gaze down two hundred feet upon the flowing water; its sides are rock, nearly perpendicular. Popular conjecture reasonably deems it the fragmentary arch of an immense limestone cave; its loftiness imparts an aspect of lightness, although at the centre it is nearly fifty feet thick, and so massive is the whole that over it passes a public road, so that by keeping in the middle one might cross unaware of the marvel. To realize its height it must be viewed from beneath; from the side of the creek it has a Gothic aspect; its immense walls, clad with forest-trees, its dizzy elevation, buttress-like masses, and aërial symmetry make this sublime arch one of those objects which impress the imagination with grace and grandeur all the more impressive because the mysterious work of Nature,—eloquent of the ages, and instinct with the latent forces of the universe. Equally remarkable, but in a diverse style, is the Giant's Causeway, whose innumerable black stone columns rise from two to four hundred feet above the water's edge in the County of Antrim, on the north coast of Ireland. These basaltic pillars are for the most part pentagonal, whose five sides are closely united, not in one conglomerate mass, but, articulated so aptly that to be traced the ball and socket must be disjointed.

In Switzerland what fearful ravines and foaming cascades do bridges cross! sometimes so aërial, and overhanging such precipices, as to justify to the imagination the name superstitiously bestowed on more than one, of the Devil's Bridge; while from few is a more lovely effect of near water seen than the "arrowy Rhone," as we gaze down upon its "blue rushing" beneath the bridge at Geneva. Perhaps the varied pictorial effects of bridges, at least in a city, are nowhere more striking than at Venice, whose five hundred, with their mellow tint and association with palatial architecture and streets of water, especially when revealed by the soft and radiant hues of an Italian sunset, present outlines, shapes, colors, and contrasts so harmonious and beautiful as to warm and haunt the imagination while they charm the eye. It is remarkable, as an artistic fact, how graciously these structures adapt themselves to such diverse scenes,—equally, though variously, picturesque amid the sturdy foliage and wild gorges of the Alps, the bustle, fog, and mast-forest of the Thames, and the crystal atmosphere, Byzantine edifices, and silent canals of Venice.

Whoever has truly felt the aërial perspective of Turner has attained a delicate sense of the pictorial significance of the bridge; for, as we look through his floating mists, we descry, amid Nature's most evanescent phenomena, the span, the arch, the connecting lines or masses whereby this familiar image seems to identify itself not less with Nature than with Art. Among the drawings which Arctic voyagers have brought home, many a bridge of ice, enormous and symmetrical, seems to tempt adventurous feet and to reflect a like form of fleecy cloud-land; daguerreotyped by the frost in miniature, the same structures may be traced on the window-pane; printed on the fossil and the strata of rock, in the veins of bark and the lips of shells, or floating in sunbeams, an identical design appears; and, on a summer morning, as the eye carefully roams over a lawn, how often do the most perfect little suspension-bridges hang from spear to spear of herbage, their filmy span embossed with glittering dew-drops!

It is not my intention, in these articles, to discuss a general theory of the glaciers upon physical and mechanical principles. My special studies, always limited to Natural History, have but indifferently fitted me for such a task, and quite recently the subject has been admirably treated from this point of view by Dr. Tyndall, in his charming volume entitled "Glaciers of the Alps." I have worked upon the glaciers as an amateur, devoting my summer vacations, with friends desirous of sharing my leisure, to excursions in the Alps, for the sake of relaxation from the closer application of my professional studies, and have considered them especially in their connection with geological phenomena, with a view of obtaining, by means of a thorough acquaintance with glaciers as they exist now, some insight into the glacial phenomena of past times, the distribution of drift, the transportation of boulders, etc. It was, however, impossible to treat one series of facts without some reference to the other; but such explanations as I have given of the mechanism of the glacier, in connection with its structure, are presented in the language of the unprofessional observer, without any attempt at the technicalities of the physicist. I do not wonder, therefore, that those who have looked upon the glacier chiefly with reference to the physical and mechanical principles involved in its structure and movement should have found my Natural Philosophy defective. I am satisfied with their agreement as to my correct observation of the facts, and am the less inclined to quarrel with the doubts thrown on my theory since I see that the most eminent physicists of the day do not differ from me more sharply than they do from each other. The facts will eventually test all our theories, and they form, after all, the only impartial jury to which we can appeal. In the mean while, I am not sorry that just at this moment, when recent investigations and publications have aroused new interest in the glaciers, the course of these articles brings me naturally to a discussion of the subject in its bearing upon geological questions. I shall, however, address myself especially, as I have done throughout these papers, to my unprofessional readers, who, while they admire the glaciers, may also wish to form a general idea of their structure and mode of action, as well as to know something of the important part they have played in the later geological history of our earth. It would, indeed, be out of place, were I to undertake here a discussion of the different views entertained by the various students who have investigated the glacier itself, among whom Dr. Tyndall is especially distinguished, or those of the more theoretical writers, among whom Mr. Hopkins occupies a prominent position.

We will next consider the stratification of the glacier. I have stated in my introductory remarks, that I consider this to be one of its primary and fundamental features, and I confess, that, after a careful examination of the results obtained by my successors in the field of glacial phenomena, I still believe that the original stratification of the mass of snow from which the glacier arises gives us the key to many facts of its internal structure. The ultimate features resulting from this connection are so exceedingly intricate and entangled that their relation is not easily explained. Nevertheless, I trust my readers will follow me in this Alpine excursion, where I shall try to smooth the asperities of the road for them as much as possible.

Imparted to it, at the very beginning of its formation, by the manner in which snow accumulates, and retained through all its transformations, the stratification of a glacier, however distorted, and at times almost obliterated, remains, notwithstanding, as distinct to one who is acquainted with all its phases, as is the stratified character of metamorphic rocks to the skilful geologist, even though they may be readily mistaken for plutonic masses by the common observer. Indeed, even those secondary features, as the dirt-bands, for instance, which we shall see to be intimately connected with snow-strata, and which eventually become so prominent as to be mistaken for the cause of the lines of stratification, do nevertheless tend, when properly understood, to make the evidence of stratification more permanent, and to point out its primitive lines.

On the plains, in our latitude, we rarely have the accumulated layers of several successive snow-storms preserved one above another. We can, therefore, hardly imagine with what distinctness the sequence of such beds is marked in the upper Alpine regions. The first cause of this distinction between the layers is the quality of the snow when it falls, then the immediate changes it undergoes after its deposit, then the falling of mist or rain upon it, and lastly and most efficient of all, the accumulation of dust upon its surface. One who has not felt the violence of a storm in the high mountains, and seen the clouds of dust and sand carried along with the gusts of wind passing over a mountain-ridge and sweeping through the valley beyond, can hardly conceive that not only the superficial aspect of a glacier, but its internal structure also, can be materially affected by such a cause. Not only are dust and sand thus transported in large quantities to the higher mountain-regions, but leaves are frequently found strewn upon the upper glacier, and even pine-cones, and maple-seeds flying upward on their spread wings, are scattered thousands of feet above and many miles beyond the forests where they grew.

This accumulation of sand and dust goes on all the year round, but the amount accumulated over one and the same surface is greatest during the summer, when the largest expanse of rocky wall is bare of snow and its loose soil dried by the heat so as to be easily dislodged. This summer deposit of loose inorganic materials, light enough to be transported by the wind, forms the main line of division between the snow of one year and the next, though only that of the last year is visible for its whole extent. Those of the preceding years, as we shall see hereafter, exhibit only their edges cropping out lower down one beyond another, being brought successively to lower levels by the onward motion of the glacier.

A few more details may help to make this statement clearer to my readers. Let us imagine that a fresh layer of snow has fallen in these mountain-regions, and that a deposit of dirt has been scattered over its surface, which, if any moisture arises from the melting of the snow or from the falling of rain or mist, will become more closely compacted with it. The next snow-storm deposits a fresh bed of snow, separated from the one below it by the sheet of dust just described, and this bed may, in its turn, receive a like deposit. For greater ease and simplicity of explanation, I speak here as if each successive snow-layer were thus indicated; of course this is not literally true, because snow-storms in the winter may follow each other so fast that there is no time for such a collection of foreign materials upon each newly formed surface. But whenever such a fresh snow-bed, or accumulation of beds, remains with its surface exposed for some time, such a deposit of dirt will inevitably be found upon it. This process may go on till we have a number of successive snow-layers divided from each other by thin sheets of dust. Of course, such seams, marking the stratification of snow, are as permanent and indelible as the seams of coarser materials alternating with the finest mud in a sedimentary rock.

The gradual progress of a glacier, which, though more rapid in summer than in winter, is never intermitted, must, of course, change the relation of these beds to each other. Their lower edge is annually cut off at a certain level, because the snow deposited every winter melts with the coming summer, up to a certain line, determined by the local climate of the place. But although the snow does not melt above this line, we have seen, in the preceding article, that it is prevented from accumulating indefinitely in the higher regions by its own tendency to move down to the lower valleys, and crowding itself between their walls, thus to force its way toward the outlet below. Now, as this movement is very gradual, it is evident that there must be a perceptible difference in the progress of the successive layers, the lower and older ones getting the advance of the upper and more recent ones: that is, when the snow that has covered the face of the country during one winter melts away from the glacier up to the so-called snow-line, there will be seen cropping out below and beyond that line the layers of the preceding years, which are already partially transformed into ice, and have become a part of the frozen mass of the glacier with which they are moving onward and downward. In the autumn, when the dust of a whole season has been accumulated upon the surface of the preceding winter's snow, the extent of the layer which year after year will henceforth crop out lower down, as a dirt-band, may best be appreciated.

There is still a third cause, to which the same result may possibly be due, and to which I shall refer at greater length hereafter; but as it has not, like the preceding ones, been the subject of direct observation, it must be considered as hypothetical. The admirable experiments of Dr. Tyndall have shown that water may be generated in ice by pressure, and it is therefore possible that at a lower depth in the glacier, where the incumbent weight of the mass above is sufficient to produce water, the water thus accumulated may be frozen into ice-layers. But this depends so much upon the internal temperature of the glacier, about which we know little beyond a comparatively superficial depth, that it cannot at present afford a sound basis even for conjecture.

There are, then, in the upper snow-fields three kinds of horizontal deposits: the beds of snow, the sheets of dust, and the layers of ice, alternating with each other. If, now, there were no modifying circumstances to change the outline and surface of the glacier,—if it moved on uninterruptedly through an open valley, the lower layers, forming the mass, getting by degrees the advance of the upper ones, our problem would be simple enough. We should then have a longitudinal mass of snow, inclosed between rocky walls, its surface crossed by straight transverse lines marking the annual additions to the glacier, as in the adjoining figure.