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66] ANNUAL REGISTER
at present above this unfortunate town.
   To account for the very great difference of the matters that cover Herculaneum and Pompeii, I have often thought that in the eruption of 79 the mountain must have been open in more than one place. A passage in Pliny's letter to Tacitus seems to say as much, "Interim e Vesuvio monte pluribus locis latissimæ 
"flammæ, atque incendia relucebant, 
"quorum fulgor et claritas tenebras
"noEtis pellebat:" so that very probably the matter that covers Pompeii proceeded from a mouth, or crater, much nearer to it than is the great mouth of the volcano, from whence came the matter that covers Herculaneum. This matter might nevertheless be said to have proceeded from Vesuvius, just as the eruption in the year 1760, which was quite independent of the great crater (being four miles from it), is properly called an eruption of Vesuvius.
  In the beginning of eruptions, volcanos frequently throw up water mixed with the ashes. Vesuvius did so in the eruption of 1631, according to the testimony of many contemporary writers. The same circumstance happened in 1669 according to the account of Ignazzio Sorrentino, who, by his History of Mount Vesuvius printed at Naples in 1734, has shewn himself to have been a very accurate observer of the phaenomena of the volcano, for many years that he lived at Torre del Greco, situated at the foot of it. At the beginning of the formation of the new mountain, near Puzzole, water was mixed with the ashes thrown up, as will be seen in 

two very curious and particular accounts of the formation of that mountain, which I shall have the pleasure of communicating to you presently; and in 1755 Etna threw up a quantity of water in the beginning of an eruption, as is mentioned in the letter I sent you last year upon the subject of that magnificent volcano *. Ulloa likewise mentions this circumstance of water attending the eruptions of volcanos in America. Whenever therefore I find a tufa composed exactly like that which immediately covers Herculaneum, and undoubtedly proceeded from Vesuvius, I conclude such a tufa to have been produced by water mixing with the erupted matter at the time of an explosion occasioned by subterraneous fire; and this observation, I believe, will be of more use than any other, in pointing out those parts of the present terra firma, that have been formed by explosion. I am convinced it has often happened that subterraneous fires and exhalations, after having been pent up and confined for some time, and been the cause of earthquakes, have forced their passage, and in venting themselves formed mountains of the matter that confined them, as you will see was the case near Puzzole in the year 1538, and by evident signs has been so before, in many parts of the neighbourhood of Puzzole; without creating a regular volcano. The materials of such mountains will have but little appearance of having been produced by fire, to any one unaccustomed to make observations upon the different nature of volcanos.
If it were allowed to make a com-

* Phil. Transact. Vol. LX, p. I.

For the Y E A R 1772.     [67

comparison between the earth and a human body, one might consider a country replete with combustibles occasioning explosions (which is surely the case here) to be like a body full of humours. When these humours concentre in one part, and form a great tumour out of which they are discharged freely, the body is less agitated; but when by any accident the humours are checked, and do not find a free passage through their usual channel, the body is agitated, and tumours appear in other parts of that body, but soon after the humours return again to their former channel. In a similar manner one may conceive Vesuvius to be the present great channel, through which nature discharges some of the foul humours of the earth; when these humours are checked by any accident or stoppage in this channel for any considerable time, earthquakes will be frequent in its neighbourhood, and explosions may be apprehended even at some distance from it. This was the case in the year 1538, Vesuvius having been quiet for near 400 years. There was no eruption from its great crater from the year 1139 to the great eruption of 1631, and the top of the mountain began to lose all signs of fire. As it is not foreign to my purpose, and will serve to shew how greatly they are mistaken, who place the feat of the fire in the centre or towards the top of a volcano, I will give you a curious description of the state of the crater of Vesuvius, after having been free from eruptions 492 years, as related by Bracini, who descended into it not long before the eruption of 1631: “The 
“crater was five miles in circum- 
“ ference, and about a thousand 

"paces deep; its sides were co-
"vered with brush wood, and at 
"the bottom there was a plain on 
"which cattle grazed. In the 
"woody parts, boars frequently 
"harboured; in the midst of the 
"plain, within the crater, was a
"narrow passage, through which, 
"by a winding path, you could
"descend about a mile amongst
"rocks and stones, till you came 
"to another more spacious plain
"covered with ashes: in this plain
"were three little pools, placed in 
"a triangular form, one towards
"the East, of hot water, corrosive
"and bitter beyond measure; ano-
"ther towards the West, of water
"salter than that of the sea; the
"third of hot water, that had no
"particular taste."
  The great increase of the cone of Vesuvius, from that time to this, naturally induces one to conclude, that the whole of the cone was raised in the like manner, and that the part of Vesuvius, called Somma, which is now considered as a distinct mountain from it, was composed in the same manner. This may plainly be perceived by examining its interior and exterior form, and the strata of lava and burnt matter of which it is composed. The ancients, in describing Vesuvius, never mention two mountains. Strabo, Dio, Vitruvius, all agree, that Vesuvius, in their time, shewed signs of having formerly erupted, and the first compares the crater on its top to an amphitheatre. The mountain now called Somma was, I believe, that which the ancients called Vesuvius; its outside form is conical, its inside, instead of an amphitheatre, is now like a great theatre. I suppose the eruption in Pliny's time
F 2

Transcription Notes:
the word "tufa" was originally transcribed as "tusa" but it should have remained as tufa as it relates to a porous volcanic rock which correlates to the theme of this article. ---------- Reopened for Editing 2023-05-13 16:03:59 - align left and remove [[column]] this is not a table ---------- Reopened for Editing 2023-05-14 13:34:45