In the foregoing pages it may seem strange that hardly any allusion has been made to the special characteristic of Iceland, viz., its volcanic structure, or to the numerous lava floods which, bursting forth in furious molten streams, have from time to time devastated its surface, leaving in their track a chaos of disrupted rocks, chasms, vast fissures, and subterranean caverns.

Our trip to Iceland was, however, unfortunately so limited in duration as to preclude, save in our four days' ride to the Great Geyser tract, any extension of travel in the various volcanic regions. Hence the omission. I have therefore extracted the following data relative to its principal volcanoes and their eruptions from such books of reference[a] as have been available to me.

The annexed compilation will, I think, explain to such of my readers as are not acquainted with the geological strata of Iceland, its sterile nature, the extreme poverty of its inhabitants, and the constant terror under which their existence isp. 148 passed, lest a fresh outbreak of lava should sweep away both them and their homesteads. It is somewhat singular, that although Iceland may be looked upon as a veritable mass of volcanoes and hot springs—for with the exception of some 4000 square miles of habitable ground, it may be said literally to rest on underground fires, and while the various eruptions of Etna, Vesuvius, and other volcanoes have for centuries been watched and recorded in the public papers with interest—it is only comparatively recently that the awe-inspiring volcanic eruptions of Iceland have been brought into notice. For instance, while full fifty pages in Ree's 'CyclopÆdia' are devoted to the subject of volcanoes, those of Iceland are barely touched upon; yet their eruptions are by far the most devastating on record. So limited, indeed, formerly were the researches of science in these ice-clad regions, that for long Hecla was quoted as its only volcano.

Now that the Island has attracted the further notice of geologists, it has been shown that there exist no less than twenty volcanic mountains, all of which have been in active eruption within historic times, and nearly one hundred eruptions have been chronicled as having taken place in the Island.

Although Hecla is doubtless the best known of the Iceland volcanoes, it is by no means the largest; that of 'Askja' (a basket), far surpasses it in size. This latter volcano lies in a great central desert termed 'Odaxa-hraun' or 'Misdeed Lava Desert,' covering a space of 1200 square miles, andp. 149 a most appropriate name it is, for the devastation caused by its last flood of lava is indescribable.

In one of the convulsions of this mountain in 1875, a quantity of lava five miles in circumference was disrupted, sinking into the mountain to a depth of 710 feet, and causing an earthquake which was felt all over the island. In one region, viz., that of the 'Myvatn's Oroefi' or 'Midge Lake Desert,' a fissure was opened which extended over 20 miles in a north-easterly direction, through which molten lava flowed continuously for four months after the earthquake. Although this fissure is at least 30 miles from Askja, so great was the column of fire thrown up by the eruption, that it was visible for four successive days at Reykjavik, 100 miles distant. The study of an Icelandic map will show the numerous volcanic ranges of mountains which intersect the island in almost every direction.

To the north there will be seen a wonderful volcanic tract. So vast, in fact, that Professor Johnstrup has termed it the Fire Focus of the North. To the north-east, again, is found a large lake, called 'Myvata,' or 'Midge Lake,' with a volcanic range of mountains which stretch from north to south; the most famous of these are 'Leivhnukr,' and 'Krafla,' which, after years of quiescence, poured forth such an amount of lava into the adjoining lake that for many days its waters stood at boiling heat. Other volcanoes in this region eject with terrible force a quantity of boiling mineral pitch, throwing up the dark matter completelyp. 150 enveloped in steam, accompanied by horrible rumbling noises.

Sir George Mackenzie, in his travels in Iceland, thus describes one of the deposits:—

'It is impossible,' he says, 'to convey any idea of the wonders of its terrors, or the sensations of a person even of strong nerves standing on a support which but feebly bears him, and below which fire and brimstone are in incessant action, having before his eyes tremendous proof of what is going on beneath him; enveloped in thick vapour, his ears stunned with thundering noises—such a situation can only be conceived by one who has experienced it.'

The extent of the sulphur beds too in this region are beyond calculation: they reproduce themselves every few years. In the vicinity of 'Krafla' is a curious rock, composed of obsidian, a substance which closely resembles black glass.

To the south of the Island is another volcano, termed the 'Kotlugja,' or 'Cauldron Rift,' lying among glaciers known as the 'Myrdals JÖkull,' whose eruptions, thirteen of which have been noted, are considered to have done more mischief than any others in the Island. Between the Myrdals and the 'Oroeja JÖkla' lies one of the most noted volcanoes of Iceland—the 'Skaptar-JÖkull,' whose eruption in 1783 is chronicled in all works on Iceland, as the prodigious floods of lava it poured forth in that year were unparalleled in historic times. The molten streams rushing seaward, down the rivers and valleys, the glowingp. 151 lava leaping over precipices and rocks, which in after years, when they have cooled down, resemble petrified cataracts, and now form one of the grand scenic attractions of the Island.

In Mrs Somerville's 'Physical Geography,' she vividly describes this eruption, narrating how, commencing in May 1783, it continued pouring forth its fiery streams with unabated fury until the following August. So great was the amount of vapour, that the sun was hidden for months, whilst clouds of ashes were carried hundreds of miles out to sea. The quantity of matter ejected on this occasion was calculated at from fifty to sixty thousand millions of cubic yards. The burning lava flowed in a stream in some places 20 to 30 miles broad, filling up the beds of rivers, and entering the sea at a distance of 50 miles from where the eruption occurred. Some of the rivers were not only heated to boiling point, but were dried up, and the condensed vapour fell as snow and rain. Epidemic disease followed in the wake of this fearful lava flood. It was calculated that no less than 1300 persons, and 150,000 sheep and cattle perished, 20 villages were destroyed. The eruption lasted two years.

Mr Paulson, a geologist, who visited Iceland eleven years later, found smoke still issuing from the rocks in the locality.

The heat of this eruption not only re-melted old lavas, and opened fresh subterranean caverns, but one of its streams was computed to course the plains to an extent of 50 miles, with a depth of 100 feet,p. 152 and 12 to 15 feet broad. Another stream was calculated at 40 miles long, and 7 wide. Men, their cattle and homesteads, their churches and grazing lands, were burnt up, whilst noxious vapours not only filled the air, but even shrouded the light of the sun.

The terrible convulsions which occurred in Iceland during the year 1783, were greater than those recorded at any other period. About a month previously to the convulsion of 'Skaptar-JÖkull,' a submarine volcano burst out at sea, and so much pumice stone was ejected that the sea was covered with it for 150 miles round, ships being stopped in their course, whilst a new island was thrown up, which the King of Denmark claimed, and named NyÖe, or New Island. Before the year had elapsed, however, it as speedily disappeared, leaving only a reef of rocks some 30 fathoms under water to mark its site.

But what of Hecla? which is 5000 feet high, and is situated close to the coast at the Southern end of a low valley, lying between two vast parallel table lands covered with ice.

If the eruptions of Hecla are not considered to have been quite so devastating as those just recorded of the 'Skaptar-JÖkull,' their duration has been longer, some of them having lasted six years at a time.

When Sir George Mackenzie visited Hecla, he found its principal crater 100 feet deep, and curiously enough, it contained a quantity of snow at the bottom. There are many smaller craters near its summit, the surrounding rocks, consisting chieflyp. 153 of lava and basalt, are covered with loose stones, scoria, and ashes.

A record of the eruptions of Hecla has been chronicled since the 10th century, and they number 43. One of its most violent convulsions occurred in the same year as that of the 'Skaptar-JÖkull,' viz., in 1783. At a distance of two miles from the crater, the lava flood was one mile wide, and 40 feet deep, whilst its fine dust was scattered as far as the Orkney Islands, 400 miles distant.

The mountain itself is composed of sand, grit, and ashes, several kinds of pumice stone being thrown out of it. It also ejects a quantity of a species of black jaspars, which look as if they had been burned at the extremities, while in form they resemble trees and branches. All the different kinds of lava found in volcanoes are to be met with here, such as agate, pumice stone, and both black and green lapis obsidian. These lavas are not all found near the place of eruption, but at some distance, and on their becoming cold form arches and caverns, the crust of which being hard rock. The smaller of the caverns are now used by the Icelanders for sheltering their cattle. The largest of the caves known is 5034 feet long and from 50 to 54 feet broad and from 34 to 36 feet high.

It is believed by some geologists that a subterranean channel connects the volcanic vent of Hecla with the great central one of Askja. This theory is based on the fact that a number of lava floods have burst forth simultaneously at different timesp. 154 at great distances from the volcanoes, leading to the supposition that innumerable subterranean channels exist in the neighbourhood.

The eruptions attributed to the volcano of Hecla vary much in number, some authorities saying there have been 40. Mrs Somerville quotes them at 23, and Mr Locke, in his 'Guide to Iceland,' at 17 in number. In the latter's work is given a table of most of its principal eruptions. One of these was of a singular nature; huge chasms opened in the earth, and for three days the wells and fountains became as white as milk, and new hot springs sprang into existence.

The twelfth eruption of this mountain was also of unusual violence. It occurred in January 1597. For twelve days previously to the outbreak loud reports were heard all over the Island, while no less than eighteen columns of fire were seen ascending from it during its eruption. The ashes it threw out covered half the Island.

The seventeenth eruption commenced on the 2d September 1845, and continued for seven months. On this occasion the ashes were carried over to Shetland, and the columns of smoke rising from the mountain reached a height of 14,000 Danish feet.

Such is a brief description of the tremendous forces which dominate Iceland. Here Nature works in silence for long periods beneath the crust of the earth, and then, with little or no forewarning, bursts forth in uncontrollable fury, ruthlessly devastating with its fiery streams whatever impedes its course.p. 155

Who can wonder that, under such existing terrors, the scanty inhabitants of the Island are a sad and dejected race. A people with death and terror continually at their doors can hardly be otherwise; whilst competitive industry, energy, and hopeful prosperity are alike suppressed by the constant devastations which occur.

With respect to the Thermal Springs, these must be considered as products of the same underground fires, and which form a second characteristic of Iceland.

These Springs may be divided into three kinds, viz., those of unceasing ebullition, those which are only sometimes eruptive, and wells which merely contain tepid water, though supposed to have been formerly eruptive.

Professor Bunsen, who passed eleven days by the side of the Great Geyser in Iceland, attributes the phenomenon to the molecular changes which take place in water after being subjected to heat. In such circumstances, water loses much of the air condensed in it, and the cohesion of the molecules is thereby increased, and a higher temperature required to boil it. In this state, when boiled, the production of vapour is so instantaneous as to cause an explosion.

Professor Bunsen found that the water at the bottom of the great Icelandic Geyser had a higher temperature than that of boiling water, and that this temperature increasing, finally caused its eruption.

In America, among the hot springs warmed by subterranean vapours, such as those springing fromp. 156 the sides of 'Nuerode Chilian,' the hot springs gush out through a bed of perpetual snow.

Among the hot springs of Iceland, Mr G. Loch gives an interesting description of those known as the 'Northern Geyser' and its tributary springs. One of these, the 'Uxhaver' or 'Ox Spring' is named from an Ox having fallen into it, and in a short time having been thrown out in the form of boiled beef. This hot spring emanates from an oval basin, 30 feet in circumference, and 4 feet in diameter. Its spurts are very regular, occurring about every 6 minutes, and about 10 feet high. After a spurt the water in the basin is lowered from 4 to 6 feet, but quickly refills, whilst the water thrown up is clear as crystal, and its spray glistening in the sun's rays has a most beautiful effect.

The smaller springs in this so-called 'Uxhaver' group are collected in a bed of rock 280 feet from the principal Geyser, and it is singular that although separated from it by only 300 yards of boggy ground, the springs in each bed of rock seem to have a distinct source of supply, for they are not affected by each other's spoutings. It is impossible even to enumerate the various hot springs of Iceland, as they are spread over all its volcanic region.

I must here bring my little book to a close, and if it has done no more than make my readers desire to make a personal acquaintance with this wonderful little Island, so full of natural curiosities, so abounding in ancient history, so isolated, and so quaint, it will have served its object.

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