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small parts of chalk and stone, was so dashed against the windows, that many of them were darkened with it; and the lower windows of my house were not opened till eight o'clock that morning, notwithstanding that they look to the north east, and consequently stood from the wind, and though guarded from the rain by a kind of shelf or pent house over them, were yet so covered with the particles of the water which the whirlwind cast against them, that in less than half an hour they were deprived of most of their transparency. Supposing this might be sea-water which the storm had not only dashed against our windows, but spread also over the whole country, I viewed the particles with my microscope, and found they had the figure of our common salt, but very small, because the water was little from whence those small particles proceeded ; and where the water had lain very thin upon the glass, there were indeed a great number of salt particles, but so, exceedingly fine that they almost escaped the sight through a very good microscope.
But as to the upper windows, where the rain had beat against them, and washed them, there was little or no salt to be found sticking upon them.
During the said storm, and about eight o'clock in the morning, casting my eye on my barometer, I observed that I had never seen the quicksilver so low; but half an hour after, the quicksilver began to rise, though the storm was not at all abated, at least to any appearance ; from whence I concluded that the storm would not last long; and so it happened accordingly. Some persons feared that the scattering of this salt water by the storm will do a great deal of harm to the fruits of the earth; but, for my part, I am of a quite different opinion; for I believe that a little salt spread over the surface of the earth, especially where it is heavy clay-ground, renders it very fruitful; and so it would be if the sea sand were made use of to the same purpose.
[Phil. Tran. 1704.
Volcanic Showers or Rain.
1. General Remarks. The enormous violence with which, during eruptions, the mate. rials that compose the bowels of the volcano are ejected into the atmosphere, and the disturbance which is usually communicated to the aerial regions, produce a conjoint force which is frequently sufficient to drive such materials in the course of the wind to a distance of several hundred miles; and the finer particles or dust to that of several hundred leagues. We proceed to give a few examples.
2. Shower of Ashes in the Archipelago.
By Capt. William Badily. December 6, 1631, riding at anchor in the Gulf of Volo, about ten o'clock that night, it began to rain sand or ashes, and continued till two o'clock the next morning. It was about two inches thick on the deck, so that we threw it overboard with shovels, as we did snow the day before. The quantity of a bushel we brought home, and presented to several friends, especially to the masters of the Tri. nity House. There was no wind stirring when these ashes fell; and they not only fell in the places where we were, but likewise in other parts, as ships were coming from St. John d’Acre to our port; though at that time a hundred leagues from us. We com. pared the ashes together, and found them both alike.
3. Shower of Dust that fell on a Ship between Shetland and
Iceland : in a Letter from Dr. Robert Whytt, Prof. Med.
By letters from a passenger on board a ship bound from Leith for Charlestown in South Carolina, it appears that on the night of the 23d or 24th of October last, when the weather was quite calm, a shower of dust fell on the decks, tops and sails of the ship, so that next morning they were covered thick with it. The ship at this time was between Shetland and Iceland, about twenty-five
leagues distant from the former, and which was the nearest land. This shower was probably owing to the great eruption, which happened at mount Mecla in Iceland, in October.
4. On a new kind of Rain. By the Count de Gioeni, an inhabi.
tant of the third Region of Mount Etna. Translated from the Italian.
The morning of the 24th inst. (April 1781) exhibited here a most singular phenomenon. Every place exposed to the air was found wet with a coloured cretaceous grey water, which, after evapo. rating and filtrating away, left every place covered with it to the height of two or three lines; and all the iron-work that was touched by it became rusty. The shower extended from N. IN.E. to S. & S. W. over the fields, about seventy miles in a right line from the vertex of Etna. There is nothing new in volcanos having thrown up sand, and also stones, by the violent expansive force generated within them, which sand has been carried by the wind to distant regions. But the colour and subtilty of the matter oc. casioned doubts concerning its origin; which increased from the remarkable circumstance of the water in which it came incorpo. rated; for which reasons some other principle or origin was sas. pected.
It became therefore necessary by all means to ascertain the na. ture of this matter, in order to be convinced of its origin, and of the effects it might produce. This could not be done without the help of a chemical analysis. To do this then with certainty, I en. deavoured to collect this rain from places where it was most pro. bable no heterogeneous matter would be mixed with it. I therefore chose the plant called Brassica Capitata, which having large and turned up leaves, they contained enough of this coloured water; many of these I emptied into a vessel, and left the contents to settle till the water became clear. This being separated into another vessel, I tried it with vegetable alkaline liquors and mineral acids; but could observe no decomposition by either. I then evaporated the water, to reunite the substances that might be in solution : and touching it again with the aforesaid liquors, it showed a slight effer. vescence with tbe acids. When tried with the syrup of violets, this became a pale green; so that I was persuaded it contained a calcareous salt. With the decoction of galls no precipitation was produced. The matter being afterwards dried in the shade, it appeared a very subtile, fine earth, of a cretaceous colour, but jnert, from having been diluted by the rain.
I next thought of calcining it with a slow fire, and it assumed the colour of a brick. A portion of this being put into a crucible, I applied to it a stronger heat, by which it lost almost all its acquired colour. Again, I exposed a portion of this for a longer time to a very violent heat, from which a vitrification might be expected; it remained however quite soft, and was easily bruised, but returned to its original dusky colour. From the most accurate observations of the smoke from the three calcinations, I could not discover either colour or smell that indicated any arsenical or sulphureous mixture. Having therefore calcined this matter in three portions, with three different degrees of fire, I presented a good magnet to each; it did not act either on the first or second ; a slight attrac.' tion was visible in many places on the third ; this persuaded me, that this earth contains a martial principle in a metallic form, and not in a vitriolic substance.
The nature of these substances then being discovered, their vol. canic origin appears; for iron, the more it is exposed to violent calcination, the more it is divided, by the loss of its phlogistic prin. ciple; which cannot naturally happen but in the great chimney of a volcano. Calcareous salt, being a marine salt combined with a calcareous substance by means of violent heat, cannot be otherwise composed than in a volcano. As to their dreaded effects on ani. mals and vegetables, every one knows the advantageous ase, in medicine, both of the one and the other, and this in the same form as they are thus prepared in the great laboratory of nature. Vegetables, even in flower, do not appear in the least macerated, which has formerly happened from only showers of sand.
How this volcanic production came to be mixed with water may be conceived in various ways. Etna, about its middle regions, is generally surrounded with clouds that do not always rise above its summit, which is 2900 paces above the level of the sea. This matter being thrown out, and descending on the clouds below it, may happen to mix and fall in rain with them in the usual way. It may also be conjectured, that the thick smoke which which the
volcanic matter contained might, by its rarefaction, be carried in the atmosphere by the winds, over that tract of country; and then, cooling so as to condense and become specifically heavier than the air, might descend in that coloured rain. I must, however, leave to philosophers, to whom the knowledge of natural agents belongs, the examination and explanation of 'such phænomena, confining myself to observation and chemical experiments.
P.S. On Friday the 4th of May, about a quarter past three in the afternoon, a slight shock of an earthquake was felt in the coun. try about Etna, which became more sensible at some distance from the mountain ; its direction was from north to south. The volcano had continued its flames and explosions; and the night be. fore, a columo of smoke, composed of globes as it were piled on each other, had ascended over the crater to double the height of the mountain, as far at least as one could judge at the distance of twentytwo miles, which the vertex is in a right line from this city. This remained the whole night perpendicular, only one of the globes had separated and lengthened out to the westward from the summit. Now and then all the inside of the column, and of the lengthened outpart, became illuminated by electric fire, which was of a deep red colour, and gradually went out again, beginning at the bottom, in about two seconds. The fire has continued on the crater till this day, May 8th, ejecting red-hot masses or stones, which rolling beautifully down the cone, have illuminated this region; some lava has run over from the crater towards the W.N.W. but without having force enough to burst the sides or walls of the volcano.