Journal of the Royal Geographical Society of London/Volume 1/Account of the Volcanic Island lately thrown up between Sicily and Pantellaria

3288702Journal of the Royal Geographical Society of London, Volume I — Account of the Volcanic Island lately thrown up between Sicily and PantellariaC. H. Swinburne, H. F. Senhouse and William Smith

VIII.–Account of the Volcanic Island lately thrown up between Sicily and Pantellaria. Extracted from Reports made by the British Cruizers to Admiral the Hon. Sir Henry Hotham, K.C.B.; and communicated by John Barrow, Esq., F.R.S. With a Plate.

The Neapolitan schooner, Psyche, appears first to have discovered smoke on the water where the island is now situated on the 12th of July; and from the 13th to the 16th, this continued in three distinct columns, but without fire, as far as seen from a Sardinian vessel becalmed in the neighbourhood. On the 17th, the master of the brig Adelaide, from London, distinguished fire also; and it is probable that at this period, for the first time, the land rose to the surface. On the following day, as will be seen by the annexed letter, it had already attained considerable dimensions:–

Report of Commander C. H. Swinburne, of his Majesty's Ship Rapid, to Vice-Admiral the Hon. Sir Henry Hotham, K.C.B.

'His Majesty's Sloop Rapid, at Malta, July 22, 1831.

'Sir,–I have the honour to inform you that on the 18th of July, 1851, at 4 p. m., the town of Marsala bearing by compass E. half N. 9 miles, I observed from on board his Majesty's sloop Rapid, under my command, a high irregular column of very white smoke or steam, bearing S. by E. I steered for it, and continued to do so fill 8, 15, p. m., when having gone about thirty miles by the reckoning, I saw flashes of brilliant light mingled with the smoke, which was still distinctly visible by the light of the moon.

'In a few minutes the whole column became black and larger: almost immediately afterwards several successive eruptions of lurid fire rose up amidst the smoke: they subsided, and the column then became gradually white again. As we seemed to near it fast, I shortened sail, and hove to till day-light, that I might ascertain its nature and exact position. During the night the changes from white to black, with flashes and the eruptions of fire, continued at irregular intervals, varying from half an hour to an hour. At daylight I again steered towards it, and about 5 a. m., when the smoke had for a moment cleared away at the base, I saw
Sketch of eruption of Graham Island 18th July 1831 and Chart of the Island
a small hillock, of a dark colour, a few feet above the sea. This was soon hidden again, and was only visible through the smoke at the intervals between the more violent eruptions.

'The volcano was in a constant state of activity, and appeared to be discharging dust and stones with vast columns of steam. At 7, 30, the rushing noise of the eruptions was heard. At 9, being distant from it about two miles, and the water being much discoloured with dark objects at the surface in various places, I hove to, and went in a boat to sound round and examine it. I rowed towards it, keeping on the weather side and sounding, but got no bottom till within twenty yards of the western side, where I had 18 fathoms soft bottom; this was the only sounding obtained, except from the brig, one mile true north from the centre of the island, where the depth was 130 fathoms soft dark brown mud. The crater (for it was now evident that such was its form) seemed to be composed of fine cinders, and mud of a dark brown colour; within it was to be seen, in the intervals between the eruptions, a mixture of muddy water, steam, and cinders, dashing up and down, and occasionally running into the sea over the edge of the crater, which I found, on rowing round, to be broken down to the level of the sea on the W.S.W. side, for the space of ten or twelve yards. Here I obtained a better view of the interior, which appeared to be filled with muddy water violently agitated, from which showers of hot stones or cinders were constantly shooting up a few yards, and falling into it again, but the great quantity of steam that constantly rose from it prevented my seeing the whole crater.

'A considerable stream of muddy water flowed outward through the opening, and, mingling with that of the sea, caused the disco1oration that had been observed before. I could not approach near enough to observe its temperature, but that of the sea, within ten or twelve yards of it, was only one degree higher than the average, and to the leeward of the island, in the direction of the current (which ran to the eastward), no difference could be perceived, even where the water was most discoloured; however, as a "mirage" played above it near its source, it was probably hot there. The dark objects on the surface of the sea proved to be patches of small floating cinders. The island, or crater, appeared to be seventy or eighty yards in its external diameter, and the lip as thin as it could be consistent with its height, which might be twenty feet above the sea in the highest, and six feet in the lowest part, leaving the rest for the diameter of the area within. These details could only be observed in the intervals between the great eruptions, some of which I witnessed from the boat. No words can describe their sublime grandeur; their progress was generally as follows:—After the volcano had emitted for some time its usual quantities of white steam, suddenly the whole aperture was filled with an enormous mass of hot cinders and dust, rushing upwards to the height of some hundred feet with a loud roaring noise, then falling into the sea on all sides with a still louder noise, arising in part, perhaps, from the formation of prodigious quantities of steam, which instantly took place. This steam was at first of a brown colour, having embodied a great deal of the dust; as it rose it gradually recovered its pure white colour, depositing the dust in the shape of a shower of muddy rain. While this was being accomplished, renewed eruptions of hot cinders and dust were quickly succeeding each other; while forked lightning, accompanied by rattling thunder, darted about in all directions within the column, now darkened with dust, and greatly increased in volume, and distorted by sudden gusts and whirlwinds. The latter were most frequent on the lee side, where they often made imperfect water-spouts of curious shapes. On one occasion some of the steam reached the boat: it smelt a little of sulphur, and the mud it left became a gritty sparkling dark brown powder when dry. None of the stones or cinders thrown out appeared more than half a foot in diameter, and most of them much smaller.

'From the time when the volcano was first seen, till after I left it, the barometer did not fall or rise; the sympiesometer underwent frequent but not important changes, and the temperature of the sea did not bespeak any unusual influence.'

This was its state on the 18th July. On the 22d it was again reported on by Commander Smith, of the Philomel, another of his Majesty's ships, who says, 'the N.W, part is the highest, being about 80 feet above the level of the sea, and becoming lower towards the southern extremity; the S.E. side is broken down even with the water, which keeps rushing into the crater with great noise; whence rises in turn an immense volume of white vapour, curling and spreading to an extraordinary height, intermixed, in rapid succession, with magnificent eruptions of cinders and lava thrown to the height of from four and five hundred to a thousand feet, forking and branching out as they ascend, and then pouring down with a noise like thunder, making the water a sheet of foam for a considerable distance around it. During the night the eruptions were not remarkable for a very great quantity of fire, though a constant shooting of small columns was visible, with occasional flashes of sheet lightning; when near to it to leeward, the sulphur was nearly suffocating the crews of the boats.

'The Volcano appears to be composed almost entirely of cinders, with a sprinkling of lava. of an oblong shape, about three-quarters of a mile in circumference, and from the soundings has as yet a very small base.'

Captain Senhouse of the St. Vincent, Sir Henry Hotham's flag-ship, is our last informant, who, having been detached in the Hind cutter to ascertain the exact position of the island, effected a landing on it on the 3d August, hoisted the British ensign, and called it Graham Island. His description of the eruptions differs little from those already quoted:—his account of landing, with estimate of height and other dimensions, we subjoin nearly in his own words:—

Seizing a favourable moment, we gave way with our oars. Our distance was rather greater than we could have wished, but we proceeded as quickly as the sea would allow. As we approached, some occasional jets were thrown up, but of little consequence; and a current was discovered running to the westward, and setting us farther to the right than we desired. Within twenty yards of the shore, the water appeared shoal, and the sea broke; but as there was no appearance of surf on the beach, we kept steadily on till the boat struck the ground. The Union Jack was then planted, such observations were made as the pressure of circumstances, and the imminent danger of a fresh eruption every moment, would admit of; a bucket-full of the materials of which the island seemed chiefly composed was collected; and we re-embarked.

'The form of the crater is nearly a perfect circle, and complete along its whole circumference, excepting for about two hundred and fifty yards on the S.E. side, which are broken and low not apparently above three feet high. The height of the highest part, I supposed by the eye to be about one hundred and sixty feet; a rough computation afterwards made it one hundred and eighty. The outer diameter is, I think, almost six hundred and forty yards, and the inner about four hundred. The whole circuit of the island I conceive to be from a mile and a quarter to a mile and one-third.

'The fragments brought away are compact and heavy, and the whole surface of the island is dense, and perfectly hard under the feet. No variety of stones were procured, nor any lava; neither did I see any jets or streams of lava while on the island. All the fragments were very hot when collected; and I thought the temperature of the sea close to the shore somewhat higher than farther out, although of this I was not very certain. The latitude of the island is 37° 11′ N. Longitude 12° 44′ East of Greenwich.'

We have been somewhat more minute in our extracts from these documents than the strict value of the information they contain warrants: because, by the latest accounts the island is still increasing in extent, and consequently none of the above descriptions are now accurate. But something is due to the interest of the phenomenon. It is remarkable that as far back as the 28th June, Admiral Sir Pulteney Malcolm, on his return home, and passing nearly over the present position of this volcano, experienced several severe shocks, which were attributed to earthquake. And two other facts are still more worthy of notice. A tradition exists at Malta, that a volcano existed in the same spot about the commencement of the last century; and one of the officers of the St. Vincent has an old chart of the Mediterranean, published by G. Faden, which lays down a shoal with only four fathoms on it, and called Larmour's Breakers, within a mile of the same latitude and longitude.