“A small blast furnace, constructed of fire-brick or stone, is charged with the sulphur-stone at the bottom, which is ignited, and fresh charges of the sulphur-stone are thrown in from time to time. The working holes at the sides admit a small supply of air to support combustion on the surface, by which means sufficient heat is generated to melt the sulphur, which runs off at the bottom through a pipe into an iron pot, where it solidifies.
“The third plan is suitable for treating the impure sulphur-stone, containing from 8 to 12 per cent, of sulphur. It consists of a furnace sufficiently wide to receive two rows of earthen pots—the vessels for distillation—which are arranged in pairs somewhat raised above the sole of the furnace, upon the supports so that the necks of the pots are a little above the top of the furnace. Thus the mouths of the pots are free, and having been charged from without, they are closed by the lids, cemented on, and the distillation begins. The sulphur vapours pass over by the lateral tubes to the receivers, where they condense to liquid sulphur, which flows through into a vessel filled with water, and there solidifies.”
We have indicated the three conditions under which sulphur is found. The sulphur in a gaseous state in Iceland, where, besides the large and rapid deposit of the sulphur in and upon the ground, an immense quantity escapes in the sulphureous vapour, is now entirely wasted, but with the adoption of the improved Mexican process an enormous saving would result. Now the whole of this may be recovered by condensing these vapours in clay vessels, a method practised with great success in Mexico, where in certain places the fumes escape from the soil and can be utilised only in this manner. The sulphur thus obtained is required at the mint of the city of Mexico and at the assaying works.
Sulphur is an essential product of volcanic action: now Iceland is par excellence the spot of the world where volcanic action is at its maximum, and Iceland, as a consequence, is the spot where sulphur is found most extensively. The districts round the active volcanoes of Etna, in Sicily, and Vesuvius, near Naples, supply the whole amount of sulphur now used. In seeking, then, for a new source of this commodity, we should naturally turn our attention to a volcanic district. And where in the whole world does there exist another country so pre-eminently volcanic as Iceland? Its fearful lava-tracts, its vast plains of scoriæ, volcanic dust and ashes, its pools of boiling water, its spouting geysirs, its vast caldrons of seething mud, proclaim its volcanic origin. It owes its upheaval wholly to volcanic agency, and is composed almost entirely of igneous rocks.
While these pages are passing through the press, the volcanic force has broken out in Iceland, and Skaptar Jökull burst into eruption for four days in the month of January last.
The wildest theories have been uttered respecting the modes of origin of sulphur. An inquirer, who investigated the southern Icelandic mines in a superficial manner, has thrown out a theory that the sulphur derived from Krísuvík, and other southern localities, has been produced by the action of water on the sulphurets of iron contained in the rocks. This idea, which rivalled some of the speculations of De Luc, was expressed by him in a paper read before the Society of Arts, on the 15th January 1873. The notion was, that the hidden fires of Iceland dwell in the crust of the earth, and not in its interior; that the boiling springs and mud-caldrons certainly do not derive their heat from the depths of our globe, but that the fire which nourishes them is to be found frequently at only a few feet below the surface, in fermenting matters which are deposited in certain strata! How far this theory is probable may be estimated when we glance at the converse hypothesis, which we must impress upon our readers. The lava at Myvatn is only a few feet, or at most, a few yards, thick; this is clearly shown by the fact that the gaseous vapour escapes from innumerable holes in the lava lying between the mines and the lake. The stoppage of an outlet for the upward flow of the gas has caused the outbreak of the fluid at spots far distant from the original central “crater” of the sulphur volcano. The geology of Mr Vincent is decidedly vague.
That a great volcanic diagonal line stretches from Cape Reykjanes to the lake of Myvatn, is a theory which is unproven by topographical science, and which a glance at the map, which shows the elevated hills of Lángjökull, Hofsjökull, and Vatnajökull extending across this imaginary line, is sufficient to disprove. The relative elevations of the mountains, from Snæfell on the east, to Eyjafjallajökull on the west, seem to indicate that the central line of volcanic action has been along a line parallel with the south-south-east coast, and which has left the formations in the neighbourhood of Lake Myvatn, with the small volcanic chain of Sellandafjall, Bláfjall, Hvannfell, and Búrfell, entirely to the north. The abrupt escarpment of the greater chain lies along its south-eastern strike, and the fissures along which the parallel rivers from the Jökuldalr to the Hrútafjörðará flow are, according to a well-known geological law, produced on the less inclined slopes. Whilst Mr Vincent’s theoretical geology verges on the speculative, his assertion of known geographical facts is inexact.
In 1857, when the temporary cessation of war by England led the British Government to look for fresh sources of gunpowder supply for Europe, Captain J. E. Commerell, of H.M.S. “Snake,” was sent to Iceland by the Lords Commissioners of the Admiralty to report upon the capabilities of the mines of Krísuvík and Húsavik. He found the Krísuvík mines, though comparatively close to the sea, did not possess a safe port of debarkation nearer than Hafnarfjörðr. An ex parte statement of the “objects, pleasures, and advantages” of the “truly eligible” Krísuvík sulphur mines leaves itself open to severe criticism, and the opinion of Commander Commerell that “the sulphur at Myvatn, though great in quantity, is at too great a distance from a port of embarkation to permit its extraction being carried on with any chance of competing with that from the Krísuvík mines,” may be profitably contrasted with that of A. de Capel Crowe, Esq., H.B.M.’s Consul in Copenhagen.[189]
Consul Crowe’s remarks as to the richness of these deposits are corroborated by Commander Commerell himself, who says in his report:
“I found at Námarfiall, which lies about six miles to the east of Lake Myvatn, large beds of sulphur in a very pure state; and though the quantities already deposited were very great, no signs appeared of their having been worked.”