1 ternal conftruction of the Sun, astronomers have only ventured to conjecture. "The dark spots in the Sun, for inftance, have been fuppofed to be folid bodies revolving very near its furface. They have been conjectured to be the fmoke of volcanoes, or the fcum floating upon an ocean of fluid matter. They have also been taken for clouds. They were explained to be opaque maffes fwimming in the fluid matter of the Sun; dipping down occafionally. It has been fuppofed, that a fiery liquid furrounds the Sun, and that, by its ebbing and flowing, the highest parts of it were occafionally uncovered, and appeared under the fhape of dark spots; and that, by the return of this fiery liquid, they were again covered, and in that manner fucceffively affumed different phafes." P. 47. Dr. Herfchel's opinions differ confiderably from fome of thefe fuppofitions, and eafily account for the appearances on which the rest are founded. He thinks that the fun itself is an opaque body, having its furface diverfified with mountains and vallies, proportionable in height and extent to its magnitude; that it is furrounded with a transparent atmosphere; that the lucid fubftance which we behold, is neither a liquid nor an elaftic fluid, but that it exifts in the manner of lucid clouds fwimming in the transparent atmosphere, or rather of luminous decompofitions taking place within that atmosphere. To confider fome large fpots, which have been seen on the fun, as the effects of volcanic explosion, is recurring, he obferves, to too violent and pernicious a caufe. An atmosphere, with its natural changes, accounts for the appearance of a dark belt near the equator of Jupiter; thick vapours, in our atmofphere, must prevent an inhabitant of the moon from feeing the earth, and from analogy we may reasonably fuppofe, that a fimilar cause may exclude ús, at most times, from a view of the furface of the fun. If this hypothefis be admitted, we may conclude with Dr. Herschel, that the fpots of the fun, as they are commonly called, are occafioned by openings or feparations of the lucid decompofitions in its atmosphere, as then, and in fuch parts only, the opaque body of the fun is prefented to our view. And if, in conjunction with this hypothefis, it be supposed that the furface of the fun is elevated into mountains and depreffed into vallies, the apparent contradictions of former obfervers may be easily reconciled: for when the lucid matter in the atmosphere opens over an high mountain, the fpot may seem more prominent than the fhining decompofitions; but if it separate over a valley, the spot may appear to be confiderably depreffed. Dr. Dr. H. thinks, from analogy, that the fame general concluhions may be extended to the fixed ftars; and he judges, from appearances, that the regions in which the luminous folar clouds are formed, adding thereto the elevation of the faculæ, or fpots of fuperior luftre, cannot be less than 1843, nor much more than 2765 miles in depth. IV. An Account of the late Eruption of Mount Vefuvius. In a Letter from the Right Honourable Sir William Hamilton, K. B. F. R. S. to Sir Fofeph Banks, Bart. P. R. S. Read, January 15, 1795. P. 73-116. Seven Plates. The great operations and phænomena of nature powerfully attract our attention, however fimilar they may be to others of the fame kind which we have beheld, or of which we have formed an idea from defcription. With renewed pleasure we behold her fmiling in the luxuriant landscape, or ferene expanded ocean, and with renewed awe and veneration we feel ourfelves interefted when the frowns in the ftorm, or threatens devalation by her convulfions. A conviction that defcriptions of fuch phænomena muft ever afford fatisfaction, and not any circumftances remarkable for their novelty, induced Sir William Hamilton to draw up the paper before us for the Royal Society; and, from the fame perfuafion, we think it our duty to prefent to our readers as full an account of this tremendous eruption as our limits will permit. The mountain had been remarkably quiet for feven months before its late eruption, but for fome days immediately preceding it, prognofticks of a great one were obferved by feveral perfons. Father Antonio Di Petrizzi, and others, remarked that a thick vapour furrounded the mountain, about a quarter of a mile beneath its crater. The water of the great fountain at Torre del Greco began to decrease fome days before the eruption, fo that the wheels of a corn-mill, worked by that water, moved very flowly; it was neceffary in all the other wells of the town, and its neighbourhood, to lengthen the ropes daily, in order to reach at the water; and fome of the wells became quite dry. Eight days before the eruption, a man and two boys, being in a vineyard beyond Torre del Greco (and precifely on the fpot where one of the new mouths opened, from which the principal current of lava that deftroyed the town iffued) were much alarmed by a fudden puff of fmoke that came out of the earth clofe to them, and was attended with a flight explofion. On the 12th of June, 1794, in the morning, there was a violent fall of rain, and foon after the inhabitants of Refina, D 2 fituated fituated directly over the ancient town of Herculaneum, were fenfible of a rumbling fubterraneous noife, which was not heard at Naples. But about eleven o'clock at night of the fame day, a violent fhock of an earthquake was felt at Naples; the undulatory motion was evident from eaft to weft, and appeared to Sir W. H. to have lafted near half a minute. "The fky," continues he, "which had been quite clear, was foon after covered with black clouds. The inhabitants of the towns and villages, which are very numerous at the foot of Vefuvius, felt this earthquake ftill more fenfibly, and fay, that the shock at first was from the bottom upwards, after which followed the undulation from east to west. This earthquake extended all over the Campagna Felice; and their Sicilian Majefties were pleafed to tell me, that the royal palace at Caferta, which is fifteen miles from this city (Naples) and one of the most magnificent and folid buildings in Europe (the walls being eighteen feet thick), was fhaken in fuch a manner as to cause great alarm, and that all the chamber bells rang. It was likewife much felt at Beneventum, about thirty miles from Naples; and at Ariano in Puglia, which is at a much greater diftance; both thefe towns have been often afflicted with earthquakes." "On Sunday the 15th of June, foon after ten o'clock at night, another fhock of an earthquake was felt at Naples, but did not appear to be quite fo violent as that of the 12th, nor did it laft fo long; at the fame moment a fountain of bright fire, attended with a very black fmoke and a loud report, was feen to iffue, and rife to a great height, from about the middle of the cone of Vefuvius; foon after, another of the fame kind broke out at fome little distance lower down; then, as I fuppofe, by the blowing up of a covered channel full of red-hot lava, it had the appearance as if the lava had taken its courfe directly up the steep cone of the volcano. Fresh fountains fucceeded one another haftily, and all in a direct line, tending, for about a mile and a half down, towards the towns of Refina and Torre del Greco. I could count fifteen of them, but I believe there were others obfcured by the fmoke. It feems probable that all these fountains of fire, from their being in fuch an exact line, proceeded from one and the fame long fiffure down the flanks of the mountain, and that the lava and other volcanic matter forced its way out of the wideft parts of the crack, and formed there the little mountains and craters that will be defcribed in their proper place. It is impoffible that any defcription can give an idea of this fiery fcene, or of the horrid noifes that attended this great operation of nature. It was a mixture of the loudest thunder, with inceffant reports, like thofe from a numerous heavy artillery, accompanied with a continued hollow murmur, like that of the roaring of the ocean during a violent ftorm; and added to thefe was another blowing noife, like that of the going up of a large flight of fky-rockets, and which brought to my mind also that noise which is produced by the action of the enormous bellows on the furnace of the Carron iron foundery in Scotland, and which it perfeally refembled. The frequent falling of the huge ftones and fcoriæ, which were thrown up to an incredible height from fome of the new mouths, mouths, and one of which having been fince measured by the Abbé Tata (who has published an account of this eruption) was ten feet high, and thirty-five in circumference, contributed undoubtedly to the concuffion of the earth and air, which kept all the houses at Naples for feveral hours in a conftant tremor, every door and window fhaking and rattling inceffantly, and the bells ringing. This was an awful moment! The fky, from a bright full moon and ftar light, began to be obfcured; the moon had prefently the appearance of being in an eclife, and foon after was totally loft in obfcurity. The mur mur of the prayers and lamentations of a numerous populace, forming various proceffions, and parading in the ftreets, added likewife to the horror." P. 77. Throughout this eruption, which continued in force about ten days, the fever of the mountain, as has been remarked in former eruptions, fhowed itself to be in fome measure periodical, and generally was moft violent at the break of day, at noon, and at midnight. About four o'clock in the morning of the 16th, the crater of Vefuvius began to fhow figns of being open, by fome black smoke iffing out of it; but the crater, and all the conical part, was foon involved in clouds and dark nefs, and remained fo for feveral days. Above thefe clouds, although of a great height, fresh columns of smoke were perceived often to iflue from the crater, rifing furionfly ftill higher, until the whole mafs remained in the ufual form of a pine tree; and in that gigantic mafs of heavy clouds the ferilli, or volcanic lightning, was frequently vifible, even in the day time. The courfe of the lava first threatened Refina, but being joined by freth lava that iffued from one of the new mouths, in a vineyard about a mile from the town, it ran like a torrent over the town of Torre del Greco, allowing the unfortunate inhabitants fcarcely time to fave their lives. Their goods and effects were totally abandoned; and of eighteen thousand inhabitants, every one (except about fifteen, who, from either age or infirmity could not be moved, and were overwhelmed. by the lava in their houses) escaped either to Caftel-a-mare, which was the ancient Stabiæ, or to Naples. Some, whofe houfes had been Surrounded with lava whilft they remained in them, efcaped from them and faved their lives the following day, by coming out of the tops of their houfes, and walking over the scoriæ on the furface of the red-hot lava. The town of Torre del Greco was totally deftroyed in 1631: in 1737 a dreadful lava ran within a few yards of one of the gates, and in the eruption now defcribed, the lava ran over the middle of it. Such, however, is the attachment of the inhabitants to their native fpot, that of eighteen thoufand not one gave his vote to abandon it. Although his Sicilian majefty offered offered them a more secure spot to rebuild their town on, they are obftinately employed in rebuilding it on the late and ftill fmoking lava that covers their former habitations. Towards the end of this very interefting paper, Sir William Hamilton fays, "having read every account of the former eruptions of Mount Vefuvius, I am well convinced that this eruption was by far the most violent that has been recorded after the two great eruptions of 79 and 1631, which were undoubtedly ftill more violent and deftructive. The fame phænomena attended the laft eruption as the two former abovementioned, but on a lefs fcale, and without the circumstance of the fea having retired from the coast." The plates annexed to this paper are highly finished, and afford an impreflive idea of the phænomena defcribed. V. New Obfervations in further Proof of the mountainous Inequalities, Rotation, Atmosphere, and Twilight, of the Planet Venus. By John Jerome Schroeter, Efq. Communicated by George Beft, Efq. F. R. S. (Tranflated from the German,) Read, February 19, 1795. P. 117-176. Four Plates To the obfervations here detailed, Mr. S. has prefixed a preface of nine pages, in which he examines feveral paffages of Dr. Herfchel's paper on the planet Venus, published in the Philofophical Tranfactions for 4793. Of this paper we gave an account in our fourth volume, and there noticed the paffages to which Mr. S. now objects. He fays, that "Evident misunderstanding and error appear to have chiefly occa fioned thofe affertions; which moft probably would not have been thus made, if the author had then known of my very circumstantial memoir, which was read at the jubilee of the univerfity of Erfurt, in a meeting of the Electorial Academy of Sciences, and which they ordered to be printed; and could have compared the many careful obfervations, full of matter, contained in it." Mr. S. then flates the paffages in queftion, and replies to each feparately. Immediately after the preface, Mr. S. gives a very full account of his obfervations, made about the time of the greatest eastern elongation, in the year 1793; and continued three months to the inferior conjun&tion. From thefe and his former obfervations he concludes, that the planet Venus has very confiderable mountains and elevated ridges; that the moft and the highest are in her fouthern hemisphere; and that her period of rotation is nearly 23h. 21. He also calculates that the arch of a great circle, over which the twilight of Venus's atmosphere extends, is equal to 4° 36' 28" or 4° 35' 34", a refult which confirms |
