Chapter XXIII: Section I

Let us begin this subject with an extract from Hr O. Henchel’s Report on the Icelandic Sulphur Mines, and on the Refining of the Sulphur. January 30, 1776. (Translated from the Danish).

I arrived at Krísuvík the 24th of June 1775, and immediately after my arrival I made preparations for examining the mountain of Krísuvík, with its mines and the surrounding neighbourhood. This mountain is situated two miles from the sea, the intervening space all the way from the sulphur mines being a tolerably level field, with only a few diminutive hills. The mountain stretches from north-east to south-west, and about two miles south-west from the mines it terminates in a plain, three miles of which are covered with lava. To north-east I did not examine the mountain more than three miles from the mines, because I found that in this direction the whole of it consisted of the same stuff, viz., of a very loose sandstone (Palagonite), except where the mines and the hot springs are to be found; there it consists of gypsum, and partly also of a red and blue “bolus,” which, in my opinion, has been sublimated by acid vapours, and partly thrown up by the hot springs. In some places these soft earths have become a hard stone, the cause, being, no doubt, that the access of the water has been stopped in these places, and when the acid vapours could not any more penetrate through this soft earth, it became hard by degrees.

In some places the above-mentioned gypsum is found to be tough and sticky, and when it is dried slowly it has a greasy touch; sometimes it is perfectly white, sometimes with red streaks, and one might take it for pipe-clay. One may therefore conclude, that by the acid, the effects of the rain and the sun and the rising heat, a fermentation has been brought about in this earth, and that it has thus become tough. Besides the already-mentioned variation, another kind of gypsum earth is found on the top of the mountain in hard sheets irregularly formed; here we probably see the effects of strong heat combined with absence of sufficient water, after the fermentation has taken place. In other places where this earth is saturated with sufficient acid, and partly dissolved by the same, and has, besides, a suitable or a natural degree of heat, so to speak, it is found in loose, reddish, and prismatic crystals. There is a considerable quantity of it, but it is never found deeper than from one foot to a foot and a half; the deeper you go the less solid it becomes, and at a depth of one foot it becomes quite fluid, because the heat is so strong, and the ground penetrated by warm vapours to such a degree that it cannot attain any solidity; in fire it loses its red colour. In short, this earth goes through so many changes, partly through the greater or lesser degree of heat, partly through a greater or less abundance of acids and water, and through the admixture of foreign substances, that it can almost bewilder one.

The blue “bolus” is found everywhere beside the boiling springs, and some of them are filled with it in such quantities that they are like a pot full of thick gruel. When the “bolus” has become hard it cannot be melted by the blow-pipe, but, in its natural condition, it attracts vapours from the air, and forms very fine white crystals, and at a distance they look like hoar-frost. This seems to show that this kind of stone must be impregnated with calcareous earth which has been saturated with vitriolic acid. That it must be this kind of earth in a hardened state is seen both from its form and from the flowers of pyrites that are mixed with it; for when one breaks off a piece of these earths in their soft and half-solid condition, the broken pieces have the same form, and are also interspersed with pyrites.

The red “bolus” is always found on the surface of the ground like the white gypseous earth, and is never covered by a bed of another kind; it is never mixed with the water of the boiling springs; there is no sublimated sulphur where it is found, although the subterranean heat in some such places is quite as strong as where that process actually takes place.

Several hot springs are to be found here, and most of them contain the blue “bolus,” but one contains white earth. These springs often disappear in one place, and break out again in another place where no spring has been before; the probable cause is that the narrow pipes under the ground, through which the spring is supplied with water, fill up by degrees; the strong heat transforms the water into very elastic vapours, which break through the ground where they find the least resistance, and thus a new hot spring is formed.

On a hill between the southernmost hot spring, called the Bath-room, and the more northerly springs, a hardened “bolus” is found; it is so brittle that it can easily be broken between the fingers; it is porous, and its holes are filled with hardened lime. At first I assumed this “bolus” to be a kind of lava partly dissolved by the atmosphere and the slow heat rising from the ground; the lime I took for a kind of salt, which had been embedded in the lava, and let loose by its solution, and then settled down into the holes of the “bolus.” But, upon closer examination of the solid state of this lime, and, after having tested it by aquafortis, by which it was brought to a high state of effervescence, I saw plainly it must be lime. I had tried to dissolve it in water, but without success; if it had been a salt let loose by the dissolution of the molten lava, it must have been more loose and in a somewhat crystallised state. My idea is that the lime must have been sublimated by the hot vapours when the lava was already thrown out; then it subsided into the holes of the lava and became hard. When I compared this earth with the lava of other places where volcanoes had been, from which the lava had spread far and wide, without undergoing any perceptible change or dissolution, I saw that this could never have been a lava. Although the lava of volcanic mountains is often confounded with slag produced by burning of the ground, I saw that this had never been melted to real slag; and it seemed to me therefore probable, that it must be a kind of hardened clay. I did not, however, find anything to confirm my conjecture until I came to Mývatn, where I found specimens of it in a soft and crude state.

The loose sandstone (Palagonite) already mentioned, which is found besides the most northern hot springs, is there much finer than in other places; it is of a slaty structure, and between the plates gypsum is found, so one might almost take it for alum plates. On the top of the mountain another kind of sandstone (trachyte?) is found; it is a good deal harder and burnt; it looks like millstone rocks from the Rhine, yet it is more porous; it is in irregular heaps, and never makes a whole mountain, as if it had been thrown over by earthquakes.

Near the boiling springs, where the ground is loose and porous, but especially where the heat has free ventilation through the above-mentioned gypseous earth, the sulphur is to be found. At the bottom it is dissolved and mixed with acid vapours; and when the sublimation has taken place, it becomes fixed in the outermost crust where there is a colder bed; and here it is found either in the shape of crystals, powder, or flowers; it is never deeper than one, two, or three inches under the surface, according to the greater or lesser degree of heat, or the greater or lesser porosity of the earth which forms the uppermost bed, as the sulphur bed itself, when it is in the shape of powder, is never more than three to six inches; and when in a crystallised form, never thicker than two to two and a half-inch, and three inches at the very highest.

These mines are not many, and do not cover a large space of ground; there are indeed a few spots here and there where sulphur is sublimated, but these spots are very small. The most important as well as the largest are the two mines highest up in the mountain; one of them is 120 yards long, and from 16 to 20 yards broad; the other is from 140 to 160 yards long, and from 20 to 40 yards broad. In these two mines the finest and best sulphur is found in the largest quantities. The bed covering the sulphur contains a great deal more of acids than the layer immediately below it, because the hot acid vapours rising from the depths below must keep the lower bed permanently acid and damp; the surplus acids are driven up through the sulphur, and that portion of them which does not unite with the sulphur, comes to the uppermost crust, where it is dried by the combined efforts of the sun, the air, and the wind. Here the acids are therefore more concentrated, and consequently able to dissolve some portions of the gypseous earth with which it has become united; in this condition it makes a kind of flowers of alum, which, however, are partly vitriolic or blended with iron. I tried to examine the purity of this salt by dissolving it in water. When the water had been filtered it had a green colour; thereupon precipitated with alkali, it gave a white precipitate; and when this was separated from the water, the latter became after a while quite yellow, as if it had been coloured with iron rust. This salt cannot really be called alum unless we should call it _lime-alum_. Like alum it has a nauseous taste, but more pungent and almost caustic. When, after dissolution, it has become solid by evaporation, it is not nearly as close as alum, and no crystallisation can be perceived in it.

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.

Another reason for the impurity of the sulphur is this, that a man, coming to a mine to see how the sulphur is, thrusts his spade into the ground in various places, without first carefully removing the upper earth, whereby the sulphur and the earth become mixed together. If he does not think the sulphur good or abundant enough to be dug out at that time, he leaves the mine thus disturbed; and the rising sulphur is sublimated among the disturbed lumps of earth and sulphur, and the whole becomes a compact mass; it often looks quite pure, but turns out altogether different at the refinery. Thus a single man may in one hour destroy a great many mines that might have been excellent if more carefully handled.

One more cause of the impurity of the sulphur may be found, I think, in the following circumstance. When the peasants come to a good mine they take out all the sulphur that is to be found there, and do not take care how they tread down the loose earth below the sulphur; the down-trodden earth, over which the wind sweeps freely, becomes tough and hard when the heat from below is not strong enough to break through it, and thus keep it porous; thus the mine becomes cold and useless. In other places where the heat is strong enough to force the steam through the trodden earth, there is, however, this disadvantage: _Firstly_, It takes a longer time for the sulphur to arrive at a state of perfect sublimation than if the earth had remained in its porous condition. _Secondly_, The fresh sublimation will be impure. When one steps into the loose earth, deep holes, separated by thin ridges, will be formed. When the sulphur is formed in these holes, covering the ridges as well, it is evident that all these ridges must come out with the sulphur at a subsequent digging.

Those that work the mines must therefore be ordered: _Firstly_, To remove the earth before they dig up any mine, so that nothing shall fall into the sulphur. _Secondly_, When they remove lumps of earth from the sulphur, they must carry them outside the mine. _Thirdly_, When they work a mine, they must first remove the uppermost earth; they must not completely empty any mine of its sulphur: they should leave the utmost border standing; then run a trench along the whole length of the mine, then leave a ridge standing, and run another trench, and so on until they have reached the utmost border, which they are to leave standing. Thus the wind will be prevented from having a full sweep of the mine, and thus making it cold. These trenches ought therefore to run across the course of the most frequent winds; these are here, in my opinion, a north-wester and south-easter. After one year the ridges left standing might be taken with the same precaution as mentioned above. The workmen ought therefore to be as much as possible prohibited from stepping into the mines; every digger should take with him a board to stand on while he digs, and this he should move with him as he proceeds. By these means the mines might be saved from being unequally trodden down, and the digger might escape from burning his feet, which he now frequently does, by sinking through the loose and hot soil.

On the east side of the mountain, below the above-mentioned mines, a red “bolus” begins, stretching round the mountain from south to north until it meets with a sandstone mountain; between the mountain and this ridge of “bolus” there is a little sulphur mine, and here the gypseous earth is found below the sulphur as usual. Digging up the real “bolus,” I found it to be very loose and soft; it was full of holes, like the hardened one at Krísuvík, and the holes were filled with lime, very loose and gelatinous, and slimy to the touch. Under the “bolus” the earth was in many places hollow, and one hardly dared to tread there. Very hot vapours arise from the bottom, by which these earths are sublimated, for it is quite as hot here as in the sulphur mines. This is a very interesting circumstance, and well worth observing, that there are two places lying side by side, and presenting such a difference in the stuffs driven up from the bottom by the heat, which is equally great in both places. In one, however, sulphur is sublimated along with a strong acid, and in the other the above said lime is sublimated, and not the least acid is found in it.

_Hliðar-námar._

The 15th I went to the so-called Hliðar-námar, which are about eighteen miles distant from the former ones. These are the largest of all the mines, and here too is the greatest heat; the sulphur is consequently sublimated in less time than in any of the others. At present there is a large quantity of sulphur here, but it is all in powder, or in the form of flowers; most of them are found in the mountains, as in the former places; and the sulphur bed is in many places six inches and more in thickness. The reason why the heat drives up greater quantities of sulphur here than in the former places is to be found in the looseness of the soil; it is not only much looser than in the former ones, but in some places even too loose and damp, which both makes the spot difficult to approach in order to dig, and fills the sulphur with earth and impurities, so as to make it useless. The reason why these mines are in such a good condition now is, that the sulphur brought from here to the refinery was not so well received as that which came from the Fremri-námar, or the so-called Theystarreykja-námar nearest to Húsavík. I admit that the sulphur found here is more mixed with earth and acids than in the other places; not, however, in such a degree as to offer any serious difficulties. But as the whole of the sulphur is in the form of flowers, and the earth immediately below it has nearly the same appearance, and cannot therefore be easily distinguished from the sulphur, the peasants do not, therefore, I think, separate the sulphur from the earth with as much care as where it is found in a more solid condition, and where the earth is more easily detected.

The mountain where these mines are situated stretches from north to south, and on the north side it goes a considerable distance beyond the mines. The same kinds of earth are found here as at Krísuvík, except the grey slate, of which there is none here, neither are there any variations in the gypseous earth; and very little of gypsum is to be found, which probably is owing to the higher degree of heat, or it may be because the heat has less interrupted egress, and consequently keeps the earth constantly porous. There is a larger quantity of the vitriolic alum. For the rest, the mountain consists of common sandstone. That even these mines have not been worked carefully is evident from the considerable number of ruined and cold mines.

Below the sulphur mountain on the east side there are three boiling springs; it is evident that the two farthest to the south, and situated close to each other, have been produced by an earthquake, because they are found in a rift in the mountain, and boil with such awful noise, especially the most southern one, that it can be heard 200 yards off, and the ground, which consists of bluish “bolus,” is shaken. Close to these hot springs is a large lava-tract, which spreads to the north to a considerable distance; it also winds round the southern point of the mountain, and crosses the path that leads to Fremri-námar, and spreads almost down to Reykjahlið. The ground is hot everywhere, and the hot vapours rise through the lava, and the whole is therefore continually steaming. About nine miles north of these mines is the mountain Krabla, where excellent mines are said to have been, but when the eruption of 1724 took place, it caused great destruction. One branch of the lava-stream coming from this mountain passed close by the mines on the west side and through the farm of Reykjahlið, the whole of which was destroyed, and at last the current flowed into the lake Mývatn. The lava thus produced was in various places hollow, as if the uppermost crust had been hardened by the air, and the still liquid lava which was under it flowed away. As the outmost crust cooled down by degrees, it contracted, and thus rifts were formed; in some places also it was not strong enough to support its own weight, and fell down. Crawling into these caves, I found a kind of salt which had been sublimated from the earth, and become fixed there. It had a bitter taste, and after being dissolved and dried again it formed square crystals, with a square point. It was easily melted by the blow-pipe.

_Theystarreykja Mines._

The 31st of August I came to the Theystarreykja mines, which are about two miles from the refinery. A large quantity of sulphur is said to have been brought from these mines to the refinery, as they were very important ones, but now they are almost all cold, and it is only in a few of them that sufficient heat is found. Therefore, although four years are said to have passed since sulphur was taken herefrom, there are only four or five where it might be taken again. Nevertheless the heat seems in some of the cold mines to be breaking through so far that the vitriolic acid can be sublimated through the ground, as it has in combination with the dissolved lime formed the above-mentioned vitriolic salt. It is therefore to be hoped that many of these ruined mines may recover after a time, yet this is not certain. Here is again a clear instance of how the very best mines may be ruined in a short time by careless treatment. If, therefore, the still remaining mines, either here or in other places, are to be preserved, the peasants must be prevented from digging the sulphur.

The home-field of Theystarreykir is good though small, and has a fine situation; and to the north there is a large piece of uncultivated ground which might be made useful. Close to the farm is a hill called Bæarfell, where some of the mines are situated. It begins on the south side of the most southern mines, and continues in a northerly direction, then it takes a turn to the east and then again to the north. In the corner between the eastern and southern arms of the Bæarfell the best mines are found at present. There have been a great number of mines on the west side of the mountain, but these are now cold, except a few in the middle, where the earth is tolerably loose, and the heat can therefore sublimate the sulphur. Those, however, that are on the east side of the hill are quite cold, except two small ones high up in the hill, but there is sufficient heat in all these mines; and I am therefore of opinion that sulphur may be sublimated in them for the future. Some of the western ones are also found to be considerably hot, and it may therefore be expected that these ruined mines may recover in time. On the west side of these mines there is a large tract of lava. On the north side of the Bæarfell the home-field begins, and north of that again a piece of uncultivated ground; when beyond that, the lava reappears and takes an easterly turn. On the top of the Bæarfell there is a great deal of red “bolus,” and a strong heat under it. But sulphur is never sublimated with or through the red “bolus,” therefore it is not found here. Very little of gypsum is found in these mines. The warm springs are neither deep nor very hot, and the minerals are either sandstone, or hardened like those at Krísuvík.

All the sulphur mines which I visited in the north are in the following condition: _Fremri-námar_ bad, because all the sulphur was taken away last year. _Hliðar-námar_ good, because they have been saved the most. _Theystarreykja-námar_ are worst, because the largest quantity has been taken from them. My advice is, therefore, to let _Fremri-námar_ and _Theystarreykja-námar_ rest for some time, and to work the _Hliðar-námar_ only. When these have been emptied, the former two may be worked in their turn.

_The Refining of the Sulphur._

The refinery is situated a few hundred paces from the factory of Húsavík, and consists of a sulphur hut; two store-houses, one for the raw sulphur, the other for the melted, or refined ore; a dwelling-house, with kitchen and outhouses, all built of turf according to the Icelandic fashion. The hut is about 20 feet long and 12 to 14 feet broad. In the middle of it is a small chimney, and on both sides of it two iron boilers are walled in; one is quite small, and holds only 1 cwt. of melted sulphur, the other holds 3 cwts.; the smaller one is very little used. Above the boiler a small board is inserted in the chimney, which reaches over the middle of the boiler; it has a hole at one end, through which a stick is put to stir up the sulphur; when its lowermost end reaches the bottom of the boiler, the uppermost is supported by the board, and he who stirs the sulphur can therefore move the stick more easily than if its upper end were loose. The other instruments are, an iron spade with holes, which is used for taking off the impurities floating on the molten sulphur. Then there are some wooden forms, into which the molten sulphur is poured. They are made of oak planks 3 inches thick, 12 inches broad, and 3 feet long. On one side of the two outermost planks, and on both sides of the two middle ones, three cylinder-shaped grooves are made, so that every half-cylinder groove of the two outermost corresponds with those on the middle ones, and those on the middle ones with each other. The planks are laid one on the top of the other, and kept together with an iron ring; in such a form nine bars can be made at the same time. A small iron sieve with narrow holes is put in the top of each hole, through which the sulphur is sifted when poured out from the boiler with a large iron ladle. When not used the forms are put into a tank filled with water, in order that the hot sulphur may not stick to the sides of the holes. This is completely prevented by soaking the forms in water. These are all the instruments used in the refining of the sulphur. The fuel used is some little wood sent by the Government, and for the rest peat, of which there is a good supply close by.

When the sulphur is to be purified, a slow fire is made under the boiler, and when it grows hot a small quantity, about two pounds, of raw sulphur is put in; this is stirred till it becomes hot; the fire must be slow, in order not to burn the sulphur, which might easily happen on account of the quantity of earth mixed with it. When the portion is quite dry and begins to melt, a little train-oil is poured in and stirred quickly, by which the earth unites with the oil, and floats on the top. As soon as this is melted, another portion of raw sulphur is put in; and when this is melted, another portion of oil, if required: this is easily seen; if the earth absorbed by the oil falls to pieces like ashes, it falls again into the sulphur, and oil must be poured in immediately. Thus the work is continued until the boiler is full. When the boiler is nearly filled with molten sulphur, a quantity of train-oil is poured on the top of it, and heated sufficiently. Then the fire is removed and the stirring discontinued. The impurities absorbed by the oil are removed with the iron spade described above. The forms are taken out of the water, put together, and raised on one end. The iron sieve described above is placed over the first form, and the sulphur poured over it from the boiler. When it is full the sieve is placed over the second one, then over the third, and so on.