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sometimes a white tint. These lastmentioned cracks, though deep, ilo not, as I apprehend, pass the stratum formed by the last eruption, and which, from its extreme thickness, particularly in the valley, will probably retain a great degree of heat for some years to come, as did a thick stratum of lava that ran into the fojsc grande in the year 1767.
The number and size of the ■stones, or, more properly speaking, of the fragments of lava which have been thrown out of the volcano in the course of the last eruption, and which lie scattered thick on the cone of Vesuvius, and at the foot of it, is really incredible. The largest we measured was in circumference no less than one hundred and eight English feet, and seventeen feet high. It is a solid block, and is much vitrified: in some parts of it there are large pieces of pure gjass, of a brown yellow colour, lite that of which our common bottles are made, and throughout its pores seem to be filled with perfect vitrifications of the fame sort. The spot where jt alighted is plainly marked by a deep impression almost at the soot of the cone of the volcano, and it took three bounds before it settled, as is plainly perceived by the marks it has left on the ground, and by the stones which it has pounded to atoms under its prodigious weight. When we consider the enormous size and weight of such a solid mass, thrown at least
a quarter of a mile clear of tha mouth of the volcano, we can but admire the wonderful powera of nature, of which, being so very seldom within the reach of human inspection, we are in general too. apt to judge upon much too small a scale.
Another solid block of ancient lava, sixty-sin feet in circumference, and nineteen feet high, being nearly of a spherical shape, wa» thrown out at the same time, and lies near the former. This stone, which ha* the marks of having been rounded, nay, almost polilhed, by continual rolling in torrents, or pn the sea-soore, and which yet has beeh so undoubtedly thrown out of the volcano, may be the subject of curious speculations *. Another block of soli4 lava that was thrown much farther, and lies in the valley between the cone of Vesuvius and the Hermitage, is sixteen feet high, and ninety-two feet in circumference, though it plainly appears, by ^be large fragments that lie round, and were detached from it by the shock of it* fall, that it must have been twice as considerable when in. die air.
There are thousands of very large fragments of different species of ancient and modern lavas, that lie scattered by the late explosions on the cone of Vesuvius, and in the vallies at its foot; but these three were the largest os those we measured f.
• Or may not this stone be a spherical volcanic basalt, such as one of fortyfive feet in circumference, described by Moos. Faujas de St. Fond, in p. 155 of his curious book on the subject of extinguished volcanos?
t We measured two other stones in the val'ey between Somma and Vesuvius \ the one was twenty two sect and a half long, thirteen feet and a half broad, and
We found also many fragments of those volcanic bombs that burst in the air, as mentioned in the former part of this journal; and some entire, having fallen to the ground without bursting. The fresh red-hot and liquid lava having been thrown up with numberless fragments of ancient lavas, the latter were often closely enveloped by the former; and probably when such fragments of lava were porous and full of air bubbles, as is often the cafe, the extreme outward heat 1'uddeiiJy rarefying the confined air, caused an explosion. When these fragments were of a more compact lava they did not explode, but were simply enclosed by the fresh lava, and acquired a spherical form by whirling in the air, or rolling down the steep sides of the volcano.
The shell or outward coat of the bombs that burst, and of which w« found several pieces, was always composed of fresh lava, in which many splinters of the more ancient lava that had been enclosed are seen sticking. I was much pleased with this discovery, having been greatly puzzled for an explanation of this volcanic operation, which -was new to me, and which was very frequent during the eruption oi" the 9th of August.
The phenomenon of the natural spun glass which fell at Ottaiano with the allies on the ;th of August, was likewise clearly explained to me here. I have already mentioned, that the lava thrown up by this eruption was in general more perse6tly vitrified than that of any former eruption, which appeared plainly upon a nearer ex
amination of the fragments of fresh lava, the pores of which we generally found full of a pure vitrification, aud the lcoriæ themselves, upon a close examination with a magnifying glass, appeared like a contused heap of filaments, of a foul vitrification. When a piece of the solid fresh lava had been cracked in its fall without separating entirely, we always saw capillary fibres of 'perfect glass, reaching from side to fide within the cracks. If I may be allowed a mean comparison, which, however, conveys the idea of what I wish to explain better than any other I can think of, this lava resembled a rich Parmesan cheese, which, when broken and gently separated, spins out transparent filaments from the little cells that contained the clammy liquor of which those filaments were composed. The natural spunglass then that fell at Ottaiano during this eruption, as well as that which fell in the isle of Bourbon in the year 1766, must have been formed most probably by tbo operation of such a sort of lava as has been just described, cracking and separating in the air at the time of its (-million from the craters of the volcano?, and by that means spinning out the pure vitrified matter from its pores or cells, the wind at the fame time carrying off those filaments of glass as fast as they were produced.
1 observed sticking to some very large fragments of the new lava, which were of a close grain, fomo pieces of a substance, whose texture very much resembled that of a true pumice-stone; and upon a
ten feet high; the other eleven feet and a half high, and seventy-two feet in
close examination, and having se. parated them from the lava, I perceived that this substance had actually been forced out of the minute pores of the solid stone itlielf, and was a collection of fine vitreous fibres or filaments, confounded together at the time of their being pressed out by the contraction of the large fragments of lava in cooling, and which had bent downwards by their own weight. This curious substance has the lightness of a pumice, and resembles it in nery respect, except being of a darker colour.
When the pores of the fresh solid laTa were large and filled with pure vitrified matter, we sound that matter sometimes blown into babbles on its surface, I suppose by the air which had been forced out at the time the lava contracted itself in cooling: those bubbles being thin, sliewed that this volcanic glass has the kind of transparency of our common glass bottles, and is like them of a dirty yellow coJour. I detached with a hammer some large pieces of this kind of glass, as big as my fist, which adhered to, and was incorporated with, some of the larger fragments of lava, and, though of the fame kind, from their thickness they appeared perfectly black, a:id were opaque.
Another particularity is remarkable in the lava of this eruption: many detached pieces of it are in the shape of a barleycorn, or of a plum-stone, small at each end, and thick in the middle. We picked up several, and saw many more which were too heavy for us to carry oft", for they must have weighed more than sixty pounds; some of the smaller onco did not
weigh an ounce. I suppose them to be drops from the liquid fountain of fire of the Mb of August, which might very naturally acquire such a form in their fall; but toe peasants in the neighbourhood of Vesuvius are well convinced that they are the thunder-bolts that (ell with the volcanic lightning.
We found many of the volcanic bombs, or, properly speaking, round balls of fresh lava, large and small; all of which have a nucleus, composed of a fragment of more ancient and solid lavaThere were also some other carious vitrifications, very different from any I had ever teen before, mixed with the late fallen fhuwer of huge scoria; and mailes of lava.
Though I have endeavoured to be as particular and clear as pothole in the description I have given of the curious substances produced by the late eruption of Vesuvius, yet, as specimens of those substances will explain more at one fight than I can pretend to do by wholo pages in writing, 1 sliall not fail to lend you, by the first favourable opportunity, a collection of them, which I have set apart for that purpose, particularly as I flatter myself they may serve to give some light into a hitherto obscure subject: I mean, the nature aud manner of the formation of puroicestones.
Vesuvius continues to smoke considerably, and we had a flight shock os an earthquake yesterday; so that I do not think, notwithstanding the late eruptions baring been so very considerable, that the volcano has vented itself so sufficiently as to remain long quiet.
I must now, Sir, beg your pardon if I have trespassed too much
npoa upon your time: I meant to be stort, clear, and explicit; and if, by aiming at the two latter, I have failed in the former, I hope 1 shall J>e exculed, and thin yon will please to take the will for the deed.
I am, kc.
Relation of the recent Eruption of Mount Ætna.
TOWARDS the end of January, many reiterated stocks of an earthquake were felt in different part* of Sicily; and from that time it was observed, that Ætna emitted a thick smoke from its center, which extended commonly to the east. A new eminence; was next observed on the western side of the mountain, visible at the distance of more than 50 miles, the certain sign of a local explosion.
The 28th of March and the 8th of April, the earthquakes were felt with more violence, in directioir from north to south, and the smoke of the volcano augmented considerably; insomuch that, on the a8th of April, it was perceived to rife from the crater in the form of a straight and lofty pine, its head lost in the clouds, and casting out small fragments of a bituminous pumice-stone to the circumference of more than twenty miles. This continued till the 17th of May, when the smoke suddenly ceased.
The 18th of Mny, towards noon, a violent (hock with a subterraneous trembling was heard on the mountain, and at six in the evening a mouth appeared at the foot of 8n ancient extinguished volcano, called Mount Frumento, very near the confines of the second region
of Ætna. The fire flowed from it like a river, and, entering a neighbouring valley, called Del tfdflenza, it overran, in an instant, the space of half a league in the plain del Carpintero and delle Mandre del Favo, and then precipitated itself into the valley del Neve, rising to the height of a hundred feet.
At nine o'clock the mountain opened at two places lower still, on the land called li Scoperti di Palermo. These two openings, being very near each other, soon formed but one, the fire taking a direction to the west, where the first lava flowed. They each united in the plain called de Santi; and overran the space of one third of a mile. The first lava again separated itself from the others, continuing its court alone in the valley del Udfienza, where it flowed again, although more slowly, threatening the country of la Malta, and the lands of the Cavalier, which belong to the Benedictines of Catania. The two other lavas took a direction towards Mount Parmentelli; the base of which, to the extent of about two miles, they quite surrounded, then stowing by the east of Mount del Ma/zo, they extended along the vineyards of Rugalira, and, after having successively coverrun the space of three leagues, they stopped on the 25 th of May. The greatest breadth of this branch was one mile, and its elevation about five feet.
During the night of the 26th, a new mouth opened at the foot of Mount Parmentelli, in the middle of the lava. This volcano, for more than an hour, threw out stones of a prodigious size, and to
a very a very considerable height. The til* nest opened itself a passage, (dividing into two branches, the first to the west of the Mount del Mazzo, which it enclosed, and the other along the wood and vineyards of Rugalira for about a league.
- At the end of five days the fire seemed to be diminilhed, and advanced but very slowly; but it was soon perceived again • in a very sensible degree; and on the ;th of this month Quly] threw out such a prodigious quantity, that the arm of the lava, which was then only thirty feet broad, augmented to fifty, in about half an lour, and it still continues with the fame force. But as it finds the first lava cooled, it runs upon it, raising it to the height of more than thirty sect, in throwing it up forward, and on the sides; so that if the resistance this new lava is pbliged to combat retards its pro» grels, it nevertheless extends it in breadth, and produces the fame dellructive effects.
On the surface of this lava, in almost its whose extent, we observe evaporations, or globes of fire of different colours, according to the greater or less.quantity of bitumen, sulphur, arsenic, and vitriol, of vhich the mass is composed, and ■which the chyniisis, who have analyzed it, fay is very plentiful.
The damage already caused by this eruption is estimated at 40^000 Sicilian crowns j but many persons appreheud it to be more consi
derable. The lava continues ita course towards Palermo, from whence it is now distant no more than eight miles; and this is the richest and best cultivated country of Mount Ætna.
Of tfie EffeSs of Folcanos, and of the bit Springs, in Iceland. From • Dr. Von Troil'i Letters.
WE cast anchor not far from Bessestedr, the dwellingplace of the Celebrated Sturleson, where we found two tracts of lava called Gnrde and Hualey-re-Hrawt, (for what we and the Italians call lava is in Iceland called Hrauir, from Hrintta, to flow) of which the last particularly was remarkable, since we found there, besides a whole field covered with lava, which must have been liquid in' the highest degree, whole mountains of tuff. Chance bad directed us exactly to a spot on which we could, better than on any other part os Iceland, consider the operations of a fire which had laid waste a tract of ten or twelve miles *. We spent several days here in examining every thing with so much the more pleasure; for we found ourselves, as it were, in a new \<orld.
We had now seen almost all the effects of a volcano, except the crater, from which the sire had proceeded; in order therefore to examine this likewise, we undertook a journey of twelve days to Mount Heckla itself; we travelled
• The miles mentioned by Dr. Troil are always Swedish, ten and a half of which ire equal to a degree on one of the great circles of the globe j and therefore, one Swedish mile is nearly equal to six English statute miles. Ten or
twelve mijc; are therefore sixty or seventy-two English miles.