Blackwood's Magazine/Volume 1/Issue 2/On the Fall of Volcanic Dust in the Island of Barbadoes
ON THE FALL OF VOLCANIC DUST IN THE ISLAND OF BARBADOES.
[The following excellent letter, containing an account of the fall of volcanic dust in Barbadoes, has been communicated to us by a friend.]
sir,
In compliance with your request, I have drawn up a detail of the circumstances (as far as I was an eye-witness) of the fall of volcanic dust in the island of Barbadoes, which occurred on May 1st, 1812, and which was produced by an eruption of the volcano in the neighbouring island of St Vincent, lying to leeward, or to the westward of Barbadoes.
I was at that time resident on the north-east coast of the island of Barbadoes, or in what is termed the windward part of that island, about eleven miles from the principal town. On the shore of this district, it may be proper to remark, there is almost constantly a heavy surf rolling, produced by the trade-wind impelling the sea on a coast completely iron-bound by rocks and rocky shoals.
During the night preceding May 1st, I was awakened by what I took to be signal-guns of distress from some ships wrecked at no great distance; in a very short time the explosions became so frequent, as to induce me rather to believe that they proceeded from two vessels engaging each other. In the town, these explosions, as I understood afterwards, were regarded as the discharges of cannon; so much so, that the garrison of St Ann's castle was kept under arms for the remainder of the night.
The explosions having ceased, nothing occurred to excite my attention during the remainder of the night; but when I arose, on the light of morning beginning very faintly to appear, I was struck with surprise on approaching the window, by seeing what I took to be a very dense black cloud threatening rain, as a thunder storm was not to be expected at that period of the year: the horizon, along the edge of the sea, was clearly defined by the morning light; but, immediately above it, the black cloud seemed to fringe the surface of the sea, and to cover the whole atmosphere. At this time I had not observed any fall of dust; but I was afterwards informed by my servants, that particles of dust had been falling for the greater part of the night, though in small quantity! On returning to the other part of the room, and fixing my eyes steadily on the window, I was greatly astonished by the gradual disappearance of the faint light which had been visible before, and in a few minutes afterwards, by finding that I had totally lost sight of the sash of the window—an occurrence which I well knew never takes place in the most stormy or in the darkest night of the West Indies. I groped my way to the window, and touched the glass without seeing it; and on opening the sash, I first perceived that particles of dust were flying about; but the darkness was so profound, that I could not discover the outline of the neighbouring hills, the trees around the house, or, in short, any one object. I soon after quitted the house, and found that the earth was covered with dust; that it fell in a constant thick shower, occasionally with considerable force; and that the windows, on the windward side of the house, were incrusted with it: but the darkness was so great, that a white handkerchief held close to the face could not be seen, and it was impossible for me to walk in the garden without the risk of striking against the trees or other large objects. I then first remarked a smell of some burnt matter, and I fancied I saw, or I really saw, on looking upwards attentively, a lurid red appearance of the clouds, over head, through the profound darkness.
At this time, a perfect calm, and the most remarkable stillness, uninterrupted by the usual noise of the surf of the sea, was observable, and was rendered more evident by the crash of the limbs of the trees of a very large wood which was adjacent to the house, and which formed an awful contrast to the extreme stillness of the atmosphere. On holding a lantern to some of the trees, I found that the limbs of the more flexible ones were bent almost to the ground by the weight of the dust which adhered to them. The fall of dust during the period of darkness was incessant, but at some times it was harder and thicker than at others. It ceased between twelve and one o'clock. I first began to discover the sashes of the windows, and the outlines of the trees, soon after twelve; and at one I could plainly distinguish the lurid red clouds of a fiery aspect which hung low, and swept past the island; it was at this time that I was first struck by the noise of a tremendous surf, and on looking to the sea, I evidently saw it lashing the shore, having, as it would appear, risen to its utmost height and fury from a state of perfect quiescence in the shortest possible space of time; as during the period of darkness not the slightest murmur of the sea could be heard.
The aspect of the country around was now become wintry and dreary; the sugar canes were levelled with the earth ; the smaller plants were laid prostrate: and the limbs of the trees were either broken off or bent downwards, as the wood was flexible or brittle,—and the whole surface of the soil was covered with grayish ashes to the depth of an inch.
The next morning I rode to the beach, and could clearly perceive, by the mark which the sea had left on the dust lying on the green sward, that it had risen to a height which had covered the whole of the sands, and reached the adjacent shrubs and grass. The perpendicular height which, to have effected this, it must have risen, I then measured, and I perfectly recollect that it was very great; as, however, I have left the memoranda, (which I penned at the time) of all the circumstances of this event in Barbadoes, I will not venture to state from memory that measurement.
If regard be had to the relative situation of the island of Barbadoes, it is evidently a most singular circumstance attendant on the fall of volcanic dust, that the eruption of a volcano taking place in the island of St Vincent, twenty leagues to leeward of Barbadoes, should have projected that immense mass of heavy matter to a height above the influence of the north-eastern trade-wind, so that it should have been carried in a contrary direction to it, and then have been precipitated by its gravity on the island of Barbadoes and beyond it; for in this way only can we account for the volcanic dust having made its way seemingly against the trade-wind, which, at that period of the year especially, is steady and uniform.
It is also worthy of remark, that the explosions of the volcano should have been heard at the distance of twenty leagues, though the wind was against the progress of the sound.
A long period of drought succeeded to the tall of dust, and during that period the columns of the lighter parts of the dust, which were raised and driven by the wind, proved a most unpleasant annoyance to those who were exposed to them, and exhibited a very singular appearance when viewed from any distance.
I may now notice an occurrence which took place subsequently to the tall of dust, and which I am inclined to believe was in some degree connected with that event.
As soon as the crop of corn (zea maize and holcus sorsum), and of potatoes, (sweet potato, or convolvulus batatas, of the West Indies) the planting of which had been long retarded by the preceding drought, and took place shortly after the fall of the dust, were established, swarms of caterpillars, of a variety of species, suddenly made their appearance, and destroyed the growing corn and the foliage of the potatoes. The sudden production of these animals, and their immense quantities, scarcely can be conceived. It will be sufficient to mention, that, in one instance, in a field of potatoes, not a single caterpillar was observable early in the morning, and before noon of the same day, they were discovered in such abundance as to require to be swept up and carried off in the earthen vessels used in the sugar manufactory to contain molasses, and which hold about five gallons each. The caterpillars, however, which destroyed the growing crops of corn, were neither so suddenly produced, nor in such vast numbers, as those which fed on the foliage of the potato; but successive generations of them continued to follow each other, so that scarcely any corn was reaped, and the island of Barbadoes suffered a sort of famine for many months.
How far the production of these caterpillars was connected with the presence of the volcanic dust, may be a question difficult of solution; but it may not be irrelevant to mention, that the dust had the property, from the large quantity of iron it contained, of absorbing and retaining the solar heat, so as to be painfully hot to the touch: this heated state was probably favourable to the evolution of larvæ.
As soon as the dust was mixed with the soil, or was washed from it, so as to lie in less abundance on the surface, the caterpillars gradually disappeared.
It may not be unworthy of mention, that the destruction of the foliage of the potatoes by the caterpillars did not in any degree diminish the crop: on the contrary, the return was unusually abundant, and ultimately saved Barbadoes from a continuance of the famine which the loss of the crops of corn exposed it to. From this circumstance I am induced to infer, that the dust, though it never seemed to unite intimately with the soil, had a fertilizing property. The chemical analysis of this dust is already before the public.—I have the honour to be, sir, &c.
