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70 ANNUAL REGISTER
Opposite to the Grotto del Cane, and immediately joining to the lake, rises the mountain called Astruni, which, having, as I imagine, been thrown up by an explosion of a much later date, retains the conical shape and every symptom of a volcano in much greater perfection than that I have been describing. The crater of Astruni is surrounded with a wall to confine boars and deer (this volcano having been for many years converted into a royal chace). It may be about six miles or more in circumference; in the plain at the bottom of the crater are two lakes, and in some books there is mention made of a hot spring, which I never have been able to find. There are many huge rocks of lava within the crater of Astruni, and some I have met with also in that of Agnano; the cones of both these supposed volcanos are composed of tufa and strata of loose pumice, fragments of lava and other burnt matter, exactly resembling the strata of Vesuvius. Bartholomeus Fatias, who wrote the actions of King Alphonso the First (before the new mountain had been formed near Puzzole), conjectured that Astruni had been a volcano. These are his words: Locus Neapoli quatuor millia passuum proximus, quem vulgo Listrones vocant, nos unum e Phlegreis Campis ab ardore nuncupandum putamus. There is no entrance into the crater of either Astruni or Agnano, except one, evidently made by art, and they both exactly correspond with Strabo's description of avenues; the same may be said of the Solfaterra and the Monte Gauro, or Barbaro as it is sometimes called, which I shall describe presently.
Near Astruni and towards the sea rises the Solfaterra, which not only retains its cone or crater, but much of its former heat. In the plain within the crater, smoke issues from many parts, as also from its sides; here, by means of stones and the tiles heaped over the crevices, through which the smoke passes, they collect in an aukward manner what they call sale armoniaco; and from the sand of the plain they extract sulphur and alum. This spot well attended to might certainly produce a good revenue, whereas I doubt if they have hitherto ever cleared 200l. a year by it. The hollow sound produced by throwing a heavy stone on the plain of the crater of the Solfaterra seems to indicate, that it is supported by a sort of arched natural vault; and one is induced to think that there is a pool of water beneath this vault (which boils by the heat of the subterraneous fire still deeper) by the very moist steam that issues from the cracks in the plain of the Solfaterra, which, like that of boiling water, runs off a sword or knife, presented to it, in great drops. On the outside, and at the foot of the cone of the Solfaterra, towards the lake of Agnano, water rushes out of the rocks, so hot, as to raise the quicksilver in Fahrenheit's thermometer to the degree of boiling water, a fact of which I was myself an eye-witness. This place, well worthy the observation of the curious, has been taken little notice of; it is called the Pisciarelli. The common people of Naples have great faith in the efficacy of this water, and make much use of it in all cutaneous disorders, as well as for another disorder that prevails here. It seems to be impregnated chiefly with sulphur and alum.
When

For the YEAR 1772.  71

When you approach your ear to the rocks of the Pisciarelli, from whence this water ouzes, you hear a horrid boiling noise, which seems to proceed from the huge cauldron, that may be supposed to be under the plain of the Solfattera. On the other side of the Solfaterra, next the sea, there is a rock which has communicated with the sea, till part of it was cut away to make the road to Puzzole; this was undoubtedly a considerable lava that ran from the Solfaterra when it was an active volcano. Under this rock of lava, which is more than seventy feet high, there is a stratum of pumice and ashes. Thus ancient lava is about a quarter of a mile broad; you meet with it abruptly before you come in fight of Puzzole, and it finishes as abruptly within about an hundred paces of the town. I have often thought that many quarries of stone upon explanation would be found to owe their origin to the same cause, though time may have effaced all signs of the volcano from whence they proceeded. Except this rock, which is evidently lava and full of vitrifications like that of Vesuvius, all the rocks upon the coast of Baia are of tufa.
I have observed in the lava of Vesuvius and Etna, as in this, that the bottom as well as the surface of it was rough and porus, like the cinders of scoriae from an ironfoundery, and that for about a foot from the surface and from the bottom, they were not near so solid and compact as towards the centre; which must undoubtedly proceed from the impression of the air upon the vitrified matter whilst in fusion. I mention this circumstance, as it may serve to point out true lava's with more certainty. The ancient name of the Solfaterra was, Forum Vulcani, a strong proof of its origin from subterraneous fire. The degree of heat that the Solfaterra has preserved for so many ages, seems to have calcined the stones upon cone, and in its crater, as they are very white and crumble easily in the hottest parts. 
We come next to the new mountain near Puzzole, which, being of so very late a formation, preserves its conical shape entire, and produces as yet but a very slender vegetation. It has a crater almost as deep as the cone is high, which may be near a quarter of a mile perpendicular, and is in shape a regular inverted cone. At the basis of this new mountain (which is more than three miles in circumference),  the sand upon the sea shore, and even that which is washed by the sea itself, is burning hot for above the space of an hundred yards; if you take up a handful of the sand below water, you are obliged to get rid of it directly, on account of intense heat.
I had been long very desirous of meeting with a good account of the formation of this new mountain, because, proving this mountain to have been raised by meer explosion in a plain, would prove at the same time, that all the neighboring mountains, which are composed of the same material, and have exactly or in part the same form, were raised in the like manner, and that the feat of fire, the cause of the explosion, lies deep, which I have every reason to think.
Fortunately, I lately found two very good accounts of the phaenomena that attended the explosion, which formed the new mountain,
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