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however, to complete the survey of the volcano, and to describe the phenomena of the eruption, he has omitted altogether those details of personal adventure, and those sketches of character and of scenery which render a scientific work readable to the unscientific public. His book is indeed a pure monograph of Hekla and of the eruption, and we have found no little difficulty in reducing the original scientific details to the standard of the general reader's capacity. But while this dryness of tone detracts from its merit as a popular work, it does not diminish its. value as a faithful record or exposition of the present state of the mountain, after the throes and convulsions which it has lately endured.

The first chapter is devoted to the general description of Hekla and its environs. The geological formation of this district is given at some length, but its principal features.

are,

"That a broad belt of volcanoes, running from south-west to north-east, separates the stratified trap formations of the east and west portions of Iceland. It might be imagined, that the crust of the newly upraised island had been thinnest in the centre, and that a huge rent had severed in this direction, the whole island into two portions; while within this mighty chasm, still in some parts not quite filled up, the volcanic fires have found constant vent."

Among these outlets of the pent-up forces, Hekla stands pre-eminent in history, though many of the Icelandic volcanoes exceed this mountain in height, and many, too, have caused more terrible devastations. Thus, in 1783, the Skaptar Jokul, to the north-east of Hekla, burst into violent eruption, and for two months continued to pour forth such immense torrents of lava, with showers of heated ashes and of pumice, that the pastures all around were entirely destroyed, and hundreds of human beings, with thousands of sheep and cattle, died of hunger and disease.

The volcano of Hekla is situated in the southern part of Iceland, between two of its principal rivers, the Olfus-aa, and the Markar-fliot. From the southern coast, a broad plain stretches up in this district towards the interior. Gradually, as we advance towards the north, we find the level surface broken by spurs from the adjacent mountains, and at length it changes to a swelling upland of irregular shape, traversed by numerous ancient streams of lava.

Here we observe numerous valleys and depressions, clothed with rich green vegetation, but separated by wide tracts of brown or black volcanic sand. This sand, or volcanic ash, is indeed the scourge of many districts in Iceland.

"The enormous quantities of sand and ashes, which the volcanoes to the east of this plain have thrown out, are carried by the east and north winds in clouds over this level district. The sky on such occasions becomes obscured, and all nature is wrapt in a brown mist, through which the sun's rays struggle with a faint red light. The acrid powder floating in the atmosphere, causes such violent smarting in the eyes, that it is nearly impossible to walk out in the open air, while the finer dust makes its way into the interior of the cottages, destroying the articles of food, and rendering the milk unfit for domestic use.”—(p. 5.)

The volcano of Hekla is situated about thirty English miles from the coast, between the forks of two rivers, the East and the West Rang-aa, the course of both of these streams being generally south-west.

"If we ascend from the confluence of these two rivers towards the mountain, the ground is observed to rise gradually, one lava stream covers the other, but each succeeding stream has stopped short in its progress over the preceding one, so that we ascend step by step, or by a succession of terraces, to the volcano itself. At first the growth of grass is rich and good, but soon sand and ashes predominate, and the absolute sterility of large tracts is only broken by a few prominent sandhills, which support a low scrubby dwarf vegetation of Salix arctica, and are held together by the strong roots of the Elymus arenarius. Mounting up still further, all traces of vegetation vanish, save when a slight covering of moss varies the surface of the rugged and most recent lava streams. Water too becomes scarce, for the porous nature of the lava allows the surface water to percolate through its loose texture, to issue again in copious streams from the lower edges of the lava courses, or 'Röins,' as they are termed in Iceland. Higher still, perpetual ice and snow reign pre-eminent, especially in the almost unknown districts to the north-east of Hekla, but these too are abundantly supplied with warm springs, and with jets of steam and of hot air, especially in the district between Hekla and the Markar-fliot."

The present height of Hekla is scarcely 5,000 feet; the trigonometrical survey of the Lector Gunlögsen has established it at 4,956 feet (Danish.) It is well known, however, that the height of volcanoes is constantly liable to change; the tremendous forces frequently in operation on the

summit may destroy the higher peaks; and again, at another time, may upraise from the bowels of the mountain scoria and lava to a height greater than any that had hitherto existed. But it is in the years succeeding an eruption that the greatest alteration takes place. Each new outbreak, rending the highest portions of the top, accumulates a vast heap of loosely aggregated masses on the summit and on the sides, where they often hang half suspended on the acute angle of the descent, till, loosened by the rain, and by the ever advancing process of their own disintegration, they roll down the steep declivity to the base. In this way the general height of the mountain is constantly lowered, till a fresh eruption piles up new masses on the top. Mr. Schy the estimates the diminution of the height of Hekla, subsequent to the last eruption, to be nearly 100 feet; but he has some doubts as to the accuracy of the former trigonometrical measurements. The mass of the mountain is mainly composed of lava, scoriæ, and ashes, and in most cases, the lava is remarkably loose and porous in texture. Portions of more solid lava may often be observed impacted in a breccia of tufaceous matter, with imperfect crystals of christianite.

The general direction of the Icelandic volcanoes, from south-west to north-east, is particularly well marked in the elevation of Hekla, which is prolonged to the south-west as far as the Selsund's Field, while the lower grounds are covered with vast streams or Röins of lava, of which the successive inroads have, within historical periods, gradually destroyed a rich pasture ground that formerly extended up to the very base of the great volcano itself. Three isolated portions of these farms still remain; but they suffered severely in the late eruption, and by another will be probably overwhelmed.

On the east and north of Hekla, desolation reigns pre-eminent. Enormous streams of lava cover the whole land, while numerous Raudöldur, or "red craters" of former eruption, attest the activity of the volcanic fires in this hideous solitude. The name of the Raudöldur, or "red crater," is sufficiently expressive, and corresponds to the "Monte Rosso" of the Italian volcanoes. Only one of these diminutive craters is to be found on the western side of Hekla. It is about two hundred feet in height, and consists of a wall of tile-red slaggy lava, surrounding a deep kettleshaped crater with nearly perpendicular sides. This wall

is complete, excepting on the north-west side, where the crater has been split from top to bottom, and a large portion of it carried away by some tremendous explosion.

The age of the different lava streams of Hekla is best determined by the amount of vegetation and of mould that they bear upon the surface. The most ancient are covered with a depth of soil sufficient to support a fair growth of grass. On those of later date, the grass is thinly scattered; but a spongy moss renders the footing tolerably secure, though it often, at the same time, hides treacherous rents and fissures in the lava. Finally, the sharp and rough masses of the newest lavas, are not only totally bare of vegetation, but present so rugged and broken a surface, that an active man cannot make his way over them at a greater rate than half an English mile per hour. It is not merely here the unevenness of the surface which obstructs the traveller's progress, but the light and porous lava breaks treacherously under the slightest pressure, and precipitates the adventurer into deep fissures which before were concealed from his sight. Long, however, before grass appears on the recent lavas, vegetation in the shape of dwarf birch wood," Birkekrat," has appeared in some of the more sheltered spots. The woods of Selsund are well known in Rangaavalle Syssel, though the birch rarely rises to the height of a man; but, to the Icelander, the smallest portion of fire-wood is of the utmost value. No inconsiderable part of the income of the owner of Selsund farm is derived from the cuttings of his forests for charcoal, a species dollar (about four shillings English) being obtained readily for a small horse load of this material. To be sure, this is not paid in hard cash, which is at all times a very scarce commodity in Iceland, but is bartered for twenty fish at four skillings each.

On the north side of the Hekla range, there is a stream of lava which cannot be traced to the craters of that mountain, and has evidently flowed from some volcanoes in the interior of the country. Some of the streams of lava in this district, appear to have been consolidated under very high pressure, and our author thinks it probable, that at one time the sea extended as a great inlet over the present Rangaavalle Syssel. The great rivers of this district have, in some cases, cut their way through pre-existing streams of lava. The most ancient lavas of Hekla are completely identical with those of the most recent date, as regards their structure, and the few minerals they contain.

In traversing the vast "Röins" on the west of Hekla, the traveller observes huge black furrows running parallel to the course of the lava stream, and separated by rugged crests of the most distorted forms. Where the lava current has been confined between two cliffs, (as in the gorge below Selsund, opposite to the now ruined farm of Næfrholt), it rises high against the perpendicular walls on either side; for the lateral portions are arrested in their course, and cooled, sooner than the central and more fluid parts, which continue their downward progress. Many of our readers may, no doubt, have witnessed the advance of a stream of lava from the craters of Vesuvius; but, by the public at large, very erroneous ideas are entertained as to the rapidity of its advance and its general appearance. A lava stream has not the aspect of a fiery torrent, dashing along with the impetuosity of a river that has newly burst its bounds, and overwhelming all things, living or dead, in its irresistible course. The progress of a current of lava is often slow, excepting when it is highly fluid, and rolls over some steep declivity. The greater the distance from the crater, the more slowly does it advance, as the mass constantly tends to cool; but, on the other hand, the stream is frequently augmented by fresh eruptions. In the broad day light, a lava stream shows little or no signs of fire, so rapidly does the outer crust form from the cooling effects of the atmosphere. Across a gentle incline, it moves very slowly, and, to use a most humble simile, it resembles not a little a huge ash heap in slow and gradual progression. We have often stood beside a lava stream in the crater of Vesuvius, so near that we could thrust our walking-stick into the moving mass, from whence we withdrew it with the end in flames, though no fire could be seen on the external surface, amid the loose heaps of blackened scoriæ. At night, however, the scene is different. Wherever the stream rolls over a steep incline, the outer crust is broken, and the fiery torrent beneath comes into view. When the lava is pouring fast out of the crater, the bright ruddy glow of the melted matter forms a long line of fire winding down the sides of the mountain, while the huge masses thrown high in air by the furious outbursts of steam, resemble vast rockets in their flight through the darkened atmosphere. But perhaps the most fearful and extraordinary spectacle, is that presented by the fiery torrent when it encounters in its course a deep and rapid river. The

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