have been found to be chiefly sal ammoniac, mixed with a smail quantity of the calx of iron: but not to betray my ignorance on this subject, and pretending to nothing more than the being an exact ocular observer, I refer you to the work itself, which accompanies this letter. Many hundred weight of the Vesuvian sal ammoniac have been collected on the mountain since the late eruption by the peasants, and sold at Naples to the refiners of metals; at first it was sold for about sixpence a pound, but, from its abundance, the price is now reduced to half that money; and a much greater quantity must have escaped in the air by evaporation.

The situation of Mount Vesuvius so near a great capital, and the facility of approaching it, has certainly afforded more opportunities of watching the operations of an active volcano, and of making ob servations upon it, than any other volcano on the face of the earth has allowed of. The Vesuvian Diary, which by my care has now been kept with great exactness, and without interruption for more than fifteen years, by the worthy and ingenious Padre Antonio Piaggi, as mentioned in the beginning of this letter, and which it is my intention to deposit in the library of the Royal Society, will also throw a great light upon this curious subject. But as there is every reason to believe, with Seneca*, that the seat of the fire that causes these eruptions of volcanoes is by no means superficial, but lies deep in the bowels of the earth, and where no eye can penetrate, it will, I fear, be ever much beyond the reach of the limited human understanding to account for them with any degree of accuracy. There are modern philosophers who propose, with as great confidence, the erecting of conductors to prevent the bad effects of earthquakes and volcanoes, and who promise themselves the same success as that which attended Dr. Franklin's conductors of lightning; for, as they say, all proceed from one and the same cause, electricity. When we reflect how many parts of the earth already inhabited have evidently been thrown up from the bottom of the sea by volcanic explosions, and the probability of there being a much greater portion under the same predicament, as yet unexplored, the vain pretensions of weak mortals to counteract such great operations, carried on surely for the

"Non ipse ex se est, sed in aliqua inferna valle conceptus exæstuat, et "alibi pascitur; in ipso monte non alimentum habet, sed viam,”—Seneca, Epist. 79.

wisest purposes by the beneficent Author of nature, appear to me to be quite ridiculous.

Let us then content ourselves with seeing, as well as we can, what we are permitted to see, and reason upon it to the best of our limited understandings, well assured that whatever is, is right.

The late sufferers at Torre del Greco, although His Sicilian Majesty, with his usual clemency, offered them a more secure spot to rebuild their town on, are obstinately employed in rebuilding it on the late and still smoking lava that covers their former habitations; and there does not appear to be any situation more exposed to the numerous dangers that must attend the neighbourhood of an active volcano than that of Torre del Greco. It was totally destroyed in 1631; and in the year 1737 a dreadful lava ran within a few yards of one of the gates of the town, and now over the middle of it; nèvertheless, such is the attachment of the inhabitants to their native spot, although attended with such imminent danger, that of 18,000 not one gave his vote to abandon it. When I was in Calabria, during the earthquakes of 1783, I observed in the Calabrese the same attachment to native soil; some of the towns that were totally destroyed by the earthquakes, and which had been ill situated in every respect, and in a bad air, were to be rebuilt; and yet it required the authority of government to oblige the inhabitants of those ruined towns to change their situation for a much better.

Upon the whole, having read every account of the former eruptions of Mount Vesuvius, I am well convinced that this eruption was by far the most violent that has been recorded after the great erup tions of 79 and 1631, which were undoubtedly still more violent and destructive. The same phenomenon attended the last eruption as the two former abovementioned, but on a less scale, and without the circumstance of the sea having retired from the coast. I remarked more than once, whilst I was in my boat, an unusual motion in the sea during the late eruption. On the 18th of June I observed, and so did my boatman, that although it was a perfect calm, the waves suddenly rose and dashed against the shore, causing a white foam, but which subsided in a few minutes. On the 15th, the night of the great eruption, the corks that support the nets of the royal tunny fishery at Portici, and which usually float upon the surface of the sea, were suddenly drawn under water, and remained so for a short space of time, which indicates, that either there must have

been at that time a swell in the sea, or a depression or sinking of the earth under it.

From what we have seen lately here, and from what we read of former eruptions of Vesuvius, and of other active volcanoes, their neighbourhood must always be attended with danger; with this consideration, the very numerous population at the foot of Vesuvius is remarkable. From Naples to Castel-a-mare, about fifteen miles, is so thickly spread with houses as to be nearly one continued street, and on the Somma side of the volcano, the towns and villages are scarcely a mile from one another; so that for thirty miles, which is the extent of the basis of Mount Vesuvius and Somma, the population may be perhaps more numerous than that of any spot of a like extent in Europe, in spite of the variety of dangers attending such a situation.

With the help of the drawings that accompany this account of the late eruption of Vesuvius, and which I can assure you to be faithful representations of what we have seen, I flatter myself I shall have enabled you to have a clear idea of it; and I flatter myself also, that the communication of such a variety of well attested phænomena as have attended this formidable eruption, may not only prove acceptable, but useful to the curious in natural history.

In a subsequent letter from Sir William Hamilton to Sir Joseph Banks, dated Castel-a-mare, anciently Stabiæ, Sept. 2, 1794, are the two following remarks, to be added to this paper.

1. Within a mile of this place the mofete are still very active, and particularly under the spot where the ancient town of Stabiæ was situated. The 24th of August, a young lad by accident falling into a well there that was dry, but full of the mephitic vapour, was im mediately suffocated; there were no signs of any hurt from the fall, as the well was shallow. This circumstance called to my mind the death of the elder Pliny, who most probably lost his life by the same sort of mephitic vapours, on this very spot, and which are active after great eruptions of Vesuvius.

2. Mr. James, a British merchant, who now lives in this neighbourhood, assured me that on Tuesday night, the 17th of June, which was the third day after the eruption of Mount Vesuvius, he was in a boat with a sail, near Torre del Greco, when the minute