Observations on Mount Vesuvius, Mount Etna, and Other Volcanos. Sir William Hamilton

LETTER I.

       Table of Contents

      To the Right Honourable the Earl of Morton, President of the Royal Society.

      Naples, June 10, 1766.

      My Lord,

      As I have attended particularly to the various changes of Mount Vesuvius, from the 17th of November 1764, the day of my arrival at this capital; I flatter myself, that my observations will not be unacceptable to your Lordship, especially as this Volcano has lately made a very considerable eruption. I shall confine myself merely to the many extraordinary appearances that have come under my own inspection, and leave their explanation to the more learned in Natural Philosophy.

      During the first twelvemonth of my being here, I did not perceive any remarkable alteration in the mountain; but I observed, the smoke from the Volcano was much more considerable in bad weather than when it was fair[1]; and I often heard (even at Naples, six miles from Vesuvius) in bad weather, the inward explosions of the mountain. When I have been at the top of Mount Vesuvius in fair weather, I have sometimes found so little smoke, that I have been able to see far down the mouth of the Volcano; the sides of which were incrusted with salts and mineral of various colors, white, green, deep and pale yellow. The smoke that issued from the mouth of the Volcano in bad weather was white, very moist, and not near so offensive as the sulphureous steams from various cracks on the sides of the mountain.

      Towards the month of September last, I perceived the smoke to be more considerable, and to continue even in fair weather; and in October I perceived sometimes a puff of black smoke shoot up a considerable height in the midst of the white, which symptom of an approaching eruption grew more frequent daily; and soon after, these puffs of smoke appeared in the night tinged like clouds with the setting sun.

      About the beginning of November, I went up the mountain: it was then covered with snow; and I perceived a little hillock of sulphur had been thrown up, since my last visit there, within about forty yards of the mouth of the Volcano; it was near six feet high, and a light blue flame issued constantly from its top. As I was examining this phænomenon, I heard a violent report; and saw a column of black smoke, followed by a reddish flame, shoot up with violence from the mouth of the Volcano; and presently fell a shower of stones, one of which, falling near me, made me retire with some precipitation, and also rendered me more cautious of approaching too near, in my subsequent journies to Vesuvius.

      From November to the 28th of March, the date of the beginning of this eruption, the smoke increased, and was mixed with ashes, which fell, and did great damage to the vineyards in the neighbourhood of the mountain[2]. A few days before the eruption I saw (what Pliny the younger mentions having seen, before that eruption of Vesuvius which proved fatal to his uncle) the black smoke take the form of a pine-tree. The smoke, that appeared black in the day-time, for near two months before the eruption, had the appearance of flame in the night.

      On Good Friday, the 28th of March, at 7 o'clock at night, the lava began to boil over the mouth of the Volcano, at first in one stream; and soon after, dividing itself into two, it took its course towards Portici. It was preceded by a violent explosion, which caused a partial earthquake in the neighbourhood of the mountain; and a shower of red hot stones and cinders were thrown up to a considerable height. Immediately upon sight of the lava, I left Naples, with a party of my countrymen, whom I found as impatient as myself to satisfy their curiosity in examining so curious an operation of nature. I passed the whole night upon the mountain; and observed that, though the red hot stones were thrown up in much greater number and to a more considerable height than before the appearance of the lava, yet the report was much less considerable than some days before the eruption. The lava ran near a mile in an hour's time, when the two branches joined in a hollow on the side of the mountain, without proceeding farther. I approached the mouth of the Volcano, as near as I could with prudence; the lava had the appearance of a river of red hot and liquid metal, such as we see in the glass-houses, on which were large floating cinders, half lighted, and rolling one over another with great precipitation down the side of the mountain, forming a most beautiful and uncommon cascade; the color of the fire was much paler and more bright the first night than the subsequent nights, when it became of a deep red, probably owing to its having been more impregnated with sulphur at first than afterwards. In the day-time, unless you are quite close, the lava has no appearance of fire; but a thick white smoke marks its course.

      The 29th, the mountain was very quiet, and the lava did not continue. The 30th, it began to flow again in the same direction, whilst the mouth of the Volcano threw up every minute a girandole of red hot stones, to an immense height. The 31st, I passed the night upon the mountain: the lava was not so considerable as the first night; but the red hot stones were perfectly transparent, some of which, I dare say of a ton weight, mounted at least two hundred feet perpendicular, and fell in, or near, the mouth of a little mountain, that was now formed by the quantity of ashes and stones, within the great mouth of the Volcano, and which made the approach much safer than it had been some days before, when the mouth was near half a mile in circumference, and the stones took every direction. Mr. Hervey, brother to the Earl of Bristol, was very much wounded in the arm some