It was calculated by the writer of the memoir, that the flood for the first four miles swept along at the rate of twenty miles an hour, nearly the speed of a locomotive, and furnished about 300,000 cubic feet of water every second an efflux five times greater than that of the Rhine at Basle. In six hours and a half, it arrived at the Lake of Geneva, having passed into the Rhone, a distance of forty-five miles. Among the physical alterations effected by this debacle, there was the deposition of a stratum of alluvial matter over the whole of the lower part of the Val de Bagnes. This was several feet in thickness, and was so distributed that roads were obliged to be cut through it in some places, as when the snows have blocked up our thoroughfares. There was the transportation of an immense number of isolated masses of rock to a considerable distance, some of which must have been many tons in weight. One of these, fairly projected out of the gorge of the valley into the plain, measured twenty-seven paces round, twelve feet in height, and twelve feet across in one direction, and even larger masses bore indubitable marks of having been in motion. For some time the course of the Dranse fluctuated, and when at last it settled down into a channel, it was one widely different from that which had before been followed. Captain Hall visited Martigny a few weeks after this visitation, and found every land-mark obliterated under one uniform mass of detritus, which had levelled all distinctions in a "sweeping and democratic confusion."

The removal of loose materials, the tearing up of fragments of rock, and their transportation to a distant site, transpire under the action of those temporary torrents which are produced by heavy rains in mountainous districts. The pen of Captain Hall has sketched in a lively manner a specimen of their vigour as exhibited in the high lands behind the town of Funchal in the island of Madeira. The whole of the upper part of the mountain is split into crevices, in some instances deep enough to be called ravines, or in the larger cases even valleys, which have been cut by the rapid rush of the descending currents. Many of these crevices run into one another, so that when the rain falls in any quantity, the whole series are set in operation at once, like so many gigantic sluices, to conduct the water into the main channels which convey it into the sea. In less precipitous countries, the minor streams take some time to collect their waters; but at Madeira, where the hills are steep, the whole is done almost at a blow, and with an impetuosity that seems formidable to eyes unaccustomed to it. A few hours after a heavy rain has commenced, the torrents are all at work. Behind Funchal, the side of the mountain is indented by a valley of considerable dimensions, into which a number of ravines run, and bring down the discharges of rain from the highest ridges of the island. This is frequently the bed of a torrent, filled to the depth of twenty feet, partly with water and partly with stones, many of them of great dimensions, and moving together with a noise like continuous loud thunder. The angle which the bed makes with the horizon is sufficient to cover. the surface of the stream with waves more tumultuous than those of the Canadian rapids, bearing along rocks with the utmost velocity, which the St. Lawrence would not cause to budge an inch. Sometimes huge blocks are jerked half out of the stream by the violence with which they are dashed against one another, or against some opposing angle of the channel, the bottom and sides of which, every time the torrent is in action, undergo an amount of wear and tear which effects great changes in the course of years. The writer before referred to describes this torrent, when in full play, as the grandest thing possible, requiring an effort of considerable resolution to advance to its brink, and far surpassing the surfs, breakers, and rapids, in any part of the world, in the impression of irresistible power it makes upon the senses. The roar is such that hardly any elevation of the voice can make two persons audible to one another, though standing side by side, while the ground trembles in a manner indicating the enormous weight passing over the surface. Soon after the rain ceases, this immense

water-course becomes dry, and exhibits a pavement covered with blocks of stone, variously distributed, which the current has conveyed from the upland regions, to be transported farther when its flow is renewed.

Many remarkable cases of change produced by streams in flood might be quoted from the records of ancient and modern times. One of the rivers of the Roman plain, the Anio, now called the Teverone, has repeatedly committed extensive ravages in that land of classic recollections. Silius Italicus speaks of its gentle flow into the Tiber, but Horace gives it the epithet of præceps, impetuous or headlong, with an eye probably to its appearance in inundation. The patrician families of Rome retired to villas upon its banks in summer, attracted by the coolness of its waters, a quality mentioned by Virgil, and by the striking scenery, as at Tivoli, where the beautiful remains of the temple of Vesta, and the fall of the river, constitute a picture which has few equals. In the time of the younger Pliny, there was a flood on the Anio, which is the subject of one of his letters to Macrinus: "Is the season with you as rude and boisterous as it is with us? All here is tempest and inundation; the Tiber has swelled its channel, and overflowed its banks far and wide; though the wise precaution of the Emperor had guarded against this evil, by cutting several outlets to the river; it has nevertheless flooded all the fields and valleys, and entirely overspread the whole face of the flat country. It seems to have gone out to meet those rivers which it used to receive and carry off in one intermingled stream; and has driven them back to deluge those countries it could not reach itself. That most delightful of rivers, the Anio, which seems invited and detained in its course by the charming villas that are situated upon its banks, has almost entirely rooted up and carried away the woods which shaded its borders. It has overthrown whole mountains, and in endeavouring to find a passage through the ruins that obstructed its way, has forced down houses, and rises over the desolation it has occasioned. The inhabitants of the hill countries, who are situated above the reach of this inundation, have been the melancholy spectators of its dreadful effects, having seen costly furniture, instruments of husbandry, ploughs, and oxen with their drivers, whole herds of cattle, together with the trunks of trees, and beams of the neighbouring villas, floating about in different parts. Nor indeed have these higher places themselves, to which the waters could not rise, escaped the calamity. A continued heavy rain, as destructive as the river itself, poured down in torrents upon them, and has destroyed all the enclosures which divided that fertile country. It has damaged likewise, and even overturned, some of the public buildings, where numbers had been miserably buried in the ruins." Such is Pliny's account of a rise of the Anio, probably in the first century of the Christian era. It is an interesting illustration of the constancy of natural phenomena, that after the lapse of some seventeen centuries, in the year 1826, the scene upon its banks might be described in nearly the words of the preceding relation. After heavy rains in November the river broke its bounds, at the same time permanently widening its own channel in many places, by the power of the current undermining and destroying the cliffs along its course. A considerable eminence, on which stood the church of St. Lucia, and near forty houses of the town of Tivoli, were carried away, and the precipice crowned with the relics of Vesta's temple might have shared the same fate, had the flood risen a few feet higher.

During the storm of 1829, which ravaged Morayshire and some of the neighbouring countries, a storm, which bore a more remarkable resemblance to a tropical hurricane than any which has visited our climate, at least in recent times, some striking examples occurred of the power of a strong current, in detaching fragments of rock, apparently firmly fixed in their native beds, bearing them away in a mass, and the whole district subject to the influence of the swollen waters of the Spey, Findhorn, Divie, Dee, and Dow, was, at various points, largely modified in its physical aspect. The heavy con

1

tinuous rain which descended was accompanied with violent and sudden gusts of wind, as well as with extraordinary thunder and lightning. Speaking of the appearance of the river Don, about the old Brig of Balgownie, an eye-witness, Mr. George Tulloch, of King's College, Aberdeen, remarked, that he had seen the waves of the Atlantic rolling down the Pentland Firth, and wasting their gigantic strength on the bold and iron-bound coasts of the north; but even there the impression of power was less vivid than that produced by the rush of the river, compared with which the united exertions of the human race seemed but a feeble conception. The Don, upon the premises of Mr. Farquharson, forced a mass of four or five hundred tons of stones, many of them of great size, up an inclined plane, rising six feet in ten yards; and one of nearly four tons weight,

which he had long known in a deep pool of the river, was borne upwards of a hundred yards from its place. Yet evidence appears of the transporting power of water having been in action, at some former period, in this locality, with more gigantic energy than was developed in 1829, for a block of gneiss, weighing about a hundred tons, and lying below the junction of the Divie and the Dorback, upon a shelf of schistus, was not moved an inch by the latter flood, which must have been translated to its present position, and therefore by a more formidable inundation, as there is no rock of a similar kind for a considerable distance from it. The mill at Logie, on the Findhorn, standing fifteen feet above the ordinary level of the stream, was saved by the lower story being completely filled up to the ceiling with sand by the flood, which prevented the water working within it, though it rose in the upper story three feet deep. Sir Thomas Dick Lauder, in his singularly interesting and graphic volume on this local deluge, mentions upon his own estate at Relugas the loss of ten thousand points of locality, on which hung many longcherished associations, with the memory of those who can never return to sanctify the new scenes resulting from the catastrophe. "On Sunday," he observes, "the 2d of August, I returned from church by the river walk. The day was sultry and cloudy, and a gentle shower began to fall, which hardly penetrated the canopy of leaves overhead, and but added freshness to the surrounding natural objects, and especially to the roses and rhododendrons that were flowering among the rocks; this was the beginning of the rain, that continued without intermission all the night, and for the next two days." The river walk referred to was on one of the banks of the Divie, leading down to the point of its junction with the Findhorn, a pleasure-walk which had been constructed with

especial care to conduct the line at an elevation considered to be beyond the reach of injury from floods. "The rocks and recesses of the wooded banks, and the little grassy slopes, were covered in a wild way with many thousand shrubs, of all kinds, especially with laurels, rhododendrons, azaleas, lilacs, and a profusion of roses, which were thriving vigorously, and beginning to bear blossoms, whilst the rocks were covered with the different saxifrages, hung with all sorts of creepers, and enamelled with a variety of garden flowers, all growing artlessly, as if sown by the hand of nature. The path was therefore considered to be not unworthy of the exquisite scenery through which it led; but the flood of the 3d and 4th of August left not one fragment of it remaining, from one end to the other. Not a tree, or shrub, or flower, or piece of soil, nay, or of moss or lichen, is to be seen beneath that boldly and sublimely sketched line of flood, that appears on either side, and from end to end of these rocks, like the awful handwriting of God on

Principal Baird, then on his way to Relugas, called to the post-boy to stop as he was crossing the Divie Bridge, that he might enjoy the view of the scenery: but "Na, na, Sir," was the reply, "these are ower kittle times to be stopping on brigs!'

The difference in the condition of Relugas immediately before and after being subjected to the action of the flood remarkably illustrates the tremendous power with which the Divie rushed down its beautiful glen. Its sloping banks were converted into perpendicular walls, and a mass of rock appears in the mid-channel which before was at the side of the stream. The offices of the house, originally more than fifty yards from the water edge, and forty feet in perpendicular height above its level, were within a yard of the crumbling precipice. The Divie was before remarkable for the depth of its pools, but owing to the accumulations of sand and gravel brought into its bed, these were so completely obliterated, that, for many weeks afterwards, a dog might have walked down its whole course, from Edenkillie Church to the Findhorn, without difficulty. The swimming pool at Relugas had a depth of sixteen feet of water; but a deposit of gravel twenty feet deep was laid in it, changing the pool into a shallow, the bottom of which was four feet higher than the former surface of the water. "The whole scene," remarks the proprietor, while enacting, "had an air of unreality about it that bewildered the senses. It was like some of those wild melodramatic exhibitions where nature's operations are out-heroded by the mechanist of a theatre, and where mountains are thrown down by artificial storms. Never did the unsubstantiality of all earthly things come so perfectly home to my conviction." What transpired in this neighbourhood may be taken as a sample of the changes that were produced through the wide extent of country reached by the waters of the flood. At Loch-na-mhron, a small lake, with a swampy island in the centre, a current drove into it with such force as to undermine and tear up the island, and carry it in mass to the opposite shore, where it was left stranded upon the bank. We have a record of remarkable transitions at a point of the river Nethey, extremely interesting to the geologist, the work of successive floods occurring during the interval of about a hundred years. A Company once were pounding iron-ore with their ponderous hammers, moved by active machinery, in its bed. These actors disappeared, and the river soon obliterated all traces of them and of their works, by filling up its channel there with rounded masses of stone mingled with gravel, upon which its waters were compelled to seek another bed considerably to the westward. But flood succeeded flood; and the quieter portions of each successive inundation spread over the ground, where, by degrees, they deposited a deep and fertile soil, forming a rich piece of land, the surface of which was six or eight feet above the level of the ground the works of the Company had occupied. The greater part of this beautiful flat was soon subjected to tillage; and, the seeds of some neighbouring alder trees finding their way into a portion of it, a grove speedily made its appearance. The trees grew till they became tall and majestic, and agricultural labour went on, till the

419 flood of 1829 came down, when the mantle of alluvium was torn off, the corn land and the grove were swept away, and the memorials of manufacturing industry were again exposed to the light.

The excavating power of water when confined to a channel too narrow for it, and where

White Mountain in the Alleghanies. its bed has a considerable inclination, was strikingly exemplified by an expedient resorted to by Mr. Cumming Bruce, to preserve Thomas Rhymer's Hill upon his estate. The Dornack swept nearly round this conical-shaped hill, which formed the extremity of a long and narrow peninsula, and was rapidly wearing away by the action of the stream in its floods. The level of the water on one side of the peninsula was about twenty-two feet higher than on the other, and consequently, by cutting a trench through the neck, the stream would be diverted from its old circuitous channel round the hill, and pass directly through the peninsula to that part of its bed in a line with the opening. Accordingly a cut was made, with a fall of about four feet from one end to the other, at a time when the river was of its average size. When the last dam of earth which prevented the egress of the water into the trench was struck away, "nothing," says Sir Thomas Dick Lauder, "could be more interesting and striking than this event, where the effect of a single blow was, in