Ultima Thule; or, A Summer in Iceland. vol. 2/2

by Sir Richard Francis Burton

As the sulphur is sublimated in the manner above stated, and by condensation becomes fixed in the cold earth at the surface, it will be seen that the opinion is erroneous, that sulphur is generated in earth penetrated and made porous by the air. My instructions were to find out, by blasting the rocks, whether any traces of sulphur were to be found in them; but blasting was out of the question on account of the softness of the ground, the great heat, and the large quantity of hot vapours. The rocks must, moreover, be at a great depth, since all attempts to find them with the earth-borer, which was fifteen feet in length, proved unsuccessful.

Close to the mines on the south side heat is seen to have been in the mountain formerly. Here the same kinds of stone are found as at the hot spring, and the yellowish gypseous earth as well. By some cause or another the heat has been removed somewhere else. I was convinced that sulphur must be found here, as it might have been covered with earth after the heat left; but all my diggings, both with the earth-borer and otherwise, proved unsuccessful.

With the earth-borer I tried to ascertain the difference of the beds where sulphur is sublimated, and of those where it is not, and where only a slight heat is felt. The first experiment was made in the northernmost mine. Below the sulphur I found a one-foot thick bed of the white gypseous earth; then there was a bed of fine blue “bolus,” or an earth impregnated with flowers of pyrites here and there. In this bed the heat began to increase, and when I came to a depth of three feet the bed became a little harder, but, at the same time, warmer and coarser, as if it were mixed with gravel; and thus it continued to the depth of fourteen feet, when it became a little softer.

I examined another place where no considerable heat was felt. The white gypseous earth continued to the depth of a foot and a half; and in this place it was harder and more solid than where the heat had a free egress. Then came the blue earth; uppermost it was somewhat loose, but farther down it became so hard and close that the earth-borer could hardly penetrate it; the lower down the more it became mixed with pyrites, and was filled with gravel, as it were. At the depth of twelve to thirteen feet it became a little looser as I thought. It was the same kind of earth all the way through; the heat was intense.

The third place which I examined was at the most northern point, beside a small hot spring, thick with blue earth. Uppermost there was red “bolus” to the depth of one foot; then a bed of purple and a yellowish one, three feet thick; then a purple and bluish one, one foot thick. The heat increased with the depth; here the bed became very hard, and I found the blue earth impregnated with pyrites. This bed was ten feet deep; at this depth the heat was so intense that the water trickling down from the upper beds boiled violently, and prevented all further progress.

By these experiments I found that the conditions necessary for the sublimation of the sulphur are: Firstly, A sufficient quantity of water to keep the soil loose and porous, that the sulphur may pass through it, and to drive the sulphur vapours upwards. Secondly, That the water must come from below; for when it comes from above, it cannot penetrate through the blue bed in the absence of the rising hot vapours which keep the bed porous; and in that case the bed becomes harder and harder, and prevents the sublimation of the sulphur.

I tried in several places, both with the earth-borer and otherwise, to discover some of the so-called dead mines, but without success. From the many experiments I made, I concluded that the volcanic mountains of Iceland must have been sulphur mountains or sulphur mines in the beginning; the blue bed became hard, and the sulphur vapours were thus prevented from being sublimated. Thus they became more condensed, and, at the same time, more elastic in the ground; then there arose in them a “heat-forming movement,” by which the whole ground, which is very sulphureous, became violently shaken, and subsequently ignited, causing tremendous destruction.

Mývatn.

Fremri-námar.

At Húsavík I obtained horses and workmen from the sheriff, and left that place the 9th of August, and arrived the 12th in the evening at the so-called Fremri-námar. At a distance of about one mile from the mines, there is a valley called Hellaksdalur, where there is a little grass, just so much as to give the ground a green colour, and this is the only green spot that is to be found here within a distance of many miles; yet there was not grass sufficient for the horses, but I had to bring with me hay for them, and water for the men. In this valley I spent the night, and the next morning, the 13th, I went to the mines, which are about ten Icelandic miles (11 indirect, 40 geographical) south-east from Húsavík, situated on the west side of a mountain called Herðubreið. On the top of the mountain there is a ridge or an eminence, from which there is an extensive view; but as far as the eye can reach in every direction, nothing can be seen but lava. This eminence is 1500 paces long, and equally broad, and about 120 feet high. On the top of the eminence there is a deep hollow completely round, and about 200 paces in diameter. From its shape it is called by the inhabitants a kettle. The south and west sides of this eminence, as well as the hollow itself, consist of lava, and it may therefore be concluded that the mountain has been an active volcano in olden times. On the north and east side the mines are found, and where these are the mountain consists of gypseous earth like that at Krísuvík. A large quantity of sulphur is said to have been dug from the dead mines here; but now they are rarely found, because they have been worked annually, and the sulphur is not generated afresh in these as in the live ones. Thirty paces from the end of the valley, and also on the side of the mountain, the first live mines are found. In the valley they are about 60 paces long, and from 20 to 30 broad. On the side of the mountain they are 200 paces long, and from 20 to 30 broad. On the east side of the mountain, 40 paces lower than the mines above mentioned, other live mines are found 220 paces long, and 40 to 50 paces broad. From all these the sulphur has been completely cleared away, because the sulphur found here was very good and pure. The soil is moderately damp, and the sulphur has just as much water as (when converted into steam by the heat) is sufficient to raise it up, and to keep the ground in a loose and porous condition, so the sulphur can be sublimated through it without hindrance. Yet it does not make the soil too loose; in that case, small particles of earth would rise along with the sulphur, become mixed with it, and thus make it impure. In the mines, which, according to my guide’s information, had been completely cleared of sulphur, there was already a new bed of sulphur one to two inches in thickness, but very impure. There are others which formerly yielded sulphur, now quite cold, and ruined. The destruction of the mines, as well as the impurity of the sulphur, arises from careless digging. When the peasants dig the sulphur out of a mine, and particles of earth and impurities are sticking to it, they clear away the largest lumps; but they do not take care not to let the impurities fall down where they had taken the sulphur, where some flowers of sulphur always remain. For although the uppermost sulphur is tolerably compact and crystallised, the lowest is loose. The reason is that the uppermost bed is made more and more compact by the sulphur rising from below, and the acid phlegm surrounding the sulphur vapours cannot evaporate; the small sulphur particles are thus prevented from immediate contact with each other, but are enveloped in the superfluous phlegm. This is the reason why the lowermost sulphur must remain in the shape of flowers until the hard crust is removed; then the phlegm is exposed to the air and evaporates, until the surface has become hard again. It will therefore be seen, that when the impurities fall into these loose flowers, and the fine sulphur is subsequently sublimated among them, the impurities will be imbedded in the sulphur, and must be taken out with it at a second digging.