VESUVIUS. 



found among the lavas of Vefuvius ; but they contain im- 

 bedded cryftals of leucite, vefuvian, and fommite, which are 

 almoft pecuhar to this volcano. The lavas of Vefuvius, 

 befides iron, contain alfo copper, and fome of them are faid 

 to contain a portion of gold, filver, and other metals. See 

 Volcanic ProduSs. 



Breiilak, an Itahan geologill, has given an account of 

 the prefent ilate of Vel^uvius, and an intereiUng defcription 

 of the very remarkable eruption of 1794; the molt im- 

 portant particulars of which we (hall feleA. This erup- 

 tion was fo great as to change the very form of Veluvius, as 

 we have before obferved. 



" The prefent cone of Vefuvius is truncated, fo as to form 

 an inclined plane, (loping from the N.E. to tlie S.^V. The 

 , circumference of the fummit, which forms the brim of the 

 cauldron, is about 3000 feet ; and at the bottom is diftin- 

 guiflied an oblong plain, the greateft diameter of which is 

 from E. to W. Having fmce afcended feveral times to the 

 top of the cone, I perceived that its depth had gradually 

 diminilhed, and that the bottom of the crater became 

 higher daily, owing to the different matter which falls 

 down, efpecially from the almoft perpendicular fides on the 

 E. and N. One can at this time eafily fcan the extent and 

 depth of its mouth, but occafionally it is much encum- 

 bered, and fomctimcs totally clogged. In 1755, the bottom 

 of the funnel rofe fo confiderably, that it prefented a valt 

 plain only twenty-three feet beneath the brim, and m the 

 midft of this plain was another cone from eighty to ninety 

 feet high, with a fmall crater, from which the eruptions 

 proceeded. 



" Braccini has left us a curious defcription of the ftate of 

 Vefuvius, after a long period of reft, and before the grand 

 eruption of 1631. The whole of it, or at leaft the greater 

 part of it, had become accefTible. Having himfelf defcended 

 into the crater, he fays, he found it covered with plants 

 and trees, and that a road down it was prafticable for the 

 fpace of a mile ; at this depth a very deep cavern was feen, 

 which having paifed, the way was again open for two 

 miles by a very fteep but at the fame time very fafe road, 

 owing to the trees growing near to each other. At 

 length a large plain prefented itfelf, furrounded by a num- 

 ber of grottoes and caverns, which might be entered, but 

 which the party were deterred from on account of their 

 darknefs. This plain, which was not acceffible otherwife 

 than by a very rapid (lope, nearly three miles in length, 

 muft afiuredly have been much beneath the level of the lea. 



" When the volcano is at reft, vapours are feen to arife 

 from the cauldron's brim, or from the interior of its fides, 

 which are very perceptible. 



" When the mouth of Vefuvius is obferved from any dif- 

 tance, and during the prevalence of moifture in the atmo- 

 fphere, a mafs of vapour feems to rife from it which mingles 

 with the clouds. 



" The wellern portion of Somma muft be confidered as 

 connefted with the cone of Vefuvius by a hill of fmaller 

 eminence, denominated Monte Cantaroni, on which is the 

 hermitage del Salvatore. This hill is interfered by three 

 valleys, that deferve to be examined with attention, on account 

 of the quantity of primitive fubftances which the volcano 

 has thrown thither during old eruptions. The northern 

 valley is that termed La Fofta di Pharaone, near the plain, 

 and Vallone della Vetrana, in its more elevated part, where 

 the current of lava flowed in 1785. This vale, hollowed by 

 rains, is the only interval between mount Somma .nnd moimt 

 Cantaroni. South of this vale are two others, nearly parallel, 

 the firft called Rio Cupo, the fecond Fofta Grande, which, 

 taking a diredion from eaft to weft, emerge in the plain of 

 12 



St. Jorio. Its northern fide, nearly perpendicular, rifcs 

 to a confjderable height above the valley, and being com- 

 pofed only of cemented fragments of porous lava, called 

 capillo, of maffes of fpongy lava, and other fubftances of an 

 inadhefive quality, is fiibjeft frequently to crumble and fall 

 in large quantities. Along the whole extent of the fouthern 

 fide, at its upper part, is feen an ancient current of lava, 

 which at firft fight appears to be feveral ftrata of lava im- 

 pofed one on the other, but which a little attention (hews is 

 but one current, in which horizontal chafms have been oc- 

 cafioned by refrigeration, and into which the wind has fince ■ 

 introduced a flight quantity of vegetable earth. This lava v 

 is hard and compadl ; it contains but few fragments of augite 

 or pyroxene, arid feems to be an affemblage of leucites, the 

 fuperficial cryftalline luftre of which having been impaired 

 by decompofition, makes it refemble variolite in its exterior. 

 Many detached malfes of this current have fallen to the bot- 

 tom of the valley. Each fall of matter brings down calcareous 

 ftones, mica, and mixtures of felfpar and vefuvian. The lava 

 of 1767, which threatened the villages of La Barra and St. 

 Jorio, difcharged itfelf into this valley, which it filled to a 

 certain height, and afterwards flowed further, fpreading itfelf 

 to the plain. As it is already covered by the crumblings 

 from the flank, in order to examine it, the enquirer muft 

 repair to the plain of St. .Torio, in the neighbourhood of 

 the chapel of St. Vito. Its grain is cryftallized but fine, 

 and oftentimes fo clofe as to be nearly equal to petro-filex, 

 or horn-ftone. It contains many fmall cryftals of pvroxene 

 and fragments of leucite, which is rarely found in its perfe£l 

 form of cryftalhzation. 



" The lava of La Scala paffes beneath the garden of I^a , 

 Favorita. It is of the colour of afhes, whitifh, and of a 

 cryftallized grain. It contains many cryftals of pyroxene, 

 few of leucite, and fmall pieces of felfpar, in groups in its 

 cavities. This lava, where it is hewn on the fea-fhore near 

 La Cavalleria, is worthy of attention. Under an uniform 

 bed, from fifteen to twenty feet in thicknefs, the lava is 

 found divided into ftrata of from three to four feet : thefe 

 divifions are formed by parallel and horizontal lines ; and 

 where thefe are dug down to, the lava is found to have 

 feparated itfelf fpontaneoufly into beds. Below them are 

 large prilms, commonly hexagonal, which are disjoined with 

 great eafe : in fome places thefe prifms, inftead of the lower, 

 are found in the upper part of the current. 



" The fame tendency to a bafaltic conformation, which is 

 noticed in the lava of La Scala, is obferved again in the 

 neighbouring current of Calattro. This, after pafling through 

 a defile below Vallelonga, fpreads to a broad front on reach- 

 ing the fea. What moft deferves obfervation in the lava 

 here are the fmall cryftallizations it prefents, which feem to 

 be the ohvine of Werner. It is moreover of a deeper co- 

 lour than the lava of Scala, more porous, and hke that con- 

 tains many cryftals of augite and fragments of felfpar. 



" Next to this lava is found that of the eruption of 

 1794. Of the diflferent eruptions of Vefuvius, this is the 

 moft recent, and was one of the moft confiderable. 



" Vefuvius had continued tranquil for a long time. On 

 the 1 2th of June, 1 794, towards eleven in the evening, a very 

 violent fhock of an earthquake was felt, which induced many 

 of the inhabitants of Naples to leave their houfes for the 

 night. The tranquillity of the mountain did not, however, 

 appear difturbed, either on the Tjth, 14th, or 15th, nor did 

 it exhibit any fymptom of an approaching eruption ; but 

 towards nine in the evening of the laft day many fymptomg 

 were manifefted. The houfes about the mountain expe- 

 rienced violent (hocks, which gradually increafed in force : 

 a very powerful one was felt at ten o'clock in Naples and 



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