VOLCANO. 



which ignited every thing that was combuftible. Thefe 

 mafTes were formed of liquid lava : their exterior parts were 

 become black and porous, by cooling during their fall 

 through fuch a vaft fpacc, whilll the interior retained an ex- 

 treme heat, and were perfeftly red. To add to the horror 

 of the fcene, incelFant volcanic lightning darted from the 

 black clouds that furrounded the inhabitants, and the ful- 

 phureous fmell and heat would fcarcely allow them to 

 breathe. In this fituation they remained about twenty-five 

 minutes, when the volcanic ftorm ceafed all at once, and 

 Vefuvius remained fullen and filent. 



Moil volcanoes are obferved to liave intervals of repofe of 

 longer or (horter duration. Vefuvius has been known to 

 remain inaftive for many centuries. (See Vesuvh/s. ) 

 The periods of intermiffion of Etna and the Peak of Tene- 

 riffe have extended to near a century. According to Hum- 

 boldt, the long intervals of repofe appear to charafterife 

 volcanoes highly elevated; and he adduces feveral inftances 

 in favour of this opinion ; but other inftances might be 

 ftated which oppofe it : thus, the periods of repofe of Ve- 

 fuvius have been much longer than thofe of Etna ; and 

 Vulcano, which is far lower than Vefuvius, had no eruption 

 from the fourth to the fifteenth century, or during a period 

 of eleven hundred years. 



The volcano of Stromboli is the only one at prefent 

 known, which appears to be in a ftate of conftant aftivity. 

 The mod ancient accounts of the conflagrations of Strom- 

 boli, tranfmitted by hiftory, are prior to the Chriftian era 

 about two hundred and ninety -two years ; but at what time 

 the eruptions firft commenced we are entirely ignorant. 

 Stromboli was burning in the time of Auguftus and Ti- 

 berius ; but for want of documents, we are unacquainted 

 with the ilate of this volcano for a feries of years after- 

 wards. We know, however, from various public tefti- 

 monies, that the continued eruptions have lafted fome cen- 

 turies. The crater is fituated on the fide of the mountain. 

 Spallanzani, who looked into it from an eminence immedi- 

 ately above it, fays that it has a circular conical form, and 

 Js about three hundred and forty feet in circumference at the 

 brink. To a'certain height the crater is filled with liquid 

 red-hot matter, refembling melted brafs : this is the fluid 

 lava. It appeared to be agitated by two dillinft motions : 

 the one inteftine, whirling, and tumultuous ; by the other 

 motion it was impelled upwards. The liquid matter is 

 railed fometimes with more and fometimes with lefs rapidity 

 within the crater ; and when it has reached the diftancc of 

 twenty-five feet from the upper edge, a found is heard not 

 unlike a very fliort clap of thunder ; while, at the fame in- 

 ftant, a portion of the lava, feparated into a thoufand 

 pieces, is thrown up with indefcribable fwiftnefs, accom- 

 panied with copious eruptions of fmoke and fand. 



A few moments before the report, the furface of the lava 

 is infl.ited and covered with large bubbles, fome of which are 

 feveral feet in diameter. On the burfting of thefe bubbles, 

 the detonation and fiery (hower take place. After the ex- 

 plofion, the lava finks within the crater, but foon rifcs as 

 before, and new bubbles appear, which again burll, and 

 produce new cxplofions. When the lava finks, it produces 

 little or no found ; but when it rifes, and begins to be in- 

 flated with bubbles, it is accompanied with a found like that 

 of liquor boiling vehemently in a cauldron, but greater in 

 / proportion to the magnitude of the crater. In the fmaller 

 ' and moderate ejeftions, the ftones fell into the crater, and, 

 :\t their eoUifion with the lava, produced a found fimilar to 

 that of water ftruck by a number of (laves; but in the 

 greater ejeftions, a confidcrable quantity of them fell with- 

 out the mouth of the crater. The rcdncfs of the larger 



ftones was vifibic in the air, notwidiftanding the light of the 

 fun. The lava, when it rofe or fell, emitted but little 

 fmoke ; but a great quantity iffued from the fiffures, when 

 it exploded. This difappearcd almoft inftantly after the 

 explofion, hke the fmoke from the firing of gunpowder. 

 Though the ejeftion of the larger and heavier ilones have 

 fiiort intermiffior.s, thofe of the leifer have fcarcely any. 

 Did not the eye perceive from whence thefe ftiowcrs of 

 ftone originate, they might be fuppofed to fall from the 

 flvy. The noife of the more violent eruptions, and the 

 darknefs from the afcending fmoke, prefent together the 

 image of a tempett. Durmg the night, the red-hot ftones 

 fpread hke a (heaf, and have the appearance of a beautiful 

 fire-work. 



It has been obferved of Stromboli, that the inflammation 

 is in general more confiderable in winter than in fummcr, 

 and more intenfe on the approach of, or during, ftorms than 

 in calm weather. The materials which fupply the erup- 

 tions appear to be inexhauftible ; and there is reafon to be- 

 lieve that the volcanic fires of Stromboli and Vulcano have 

 an internal communication with thofe of JElna. and more 

 diftant countries, as we (hall prefently have occafion to 

 notice. 



Boihng water and mud are occafionally thrown out of 

 volcanoes, but more frequently from the American vol- 

 canoes than from thofe in Europe. This phenomenon is 

 very different from that of mud volcanoes, more properly 

 fo called, the water ejefted from which is cold. 



The water ejefted from fire volcanoes is probably what 

 finds accefs to the deep mafs of melted lava, either from the 

 fea in the vicinity, or from the neighbouring lakes. Ve- 

 fuvius is ftated at one time to have thrown out a conlider- 

 able quantity of fait water. 



The moft remarkable circumftance attending the volcanic 

 eruptions in America is that ftated by Humboldt, who in- 

 forms us that great quantities of fifli are fometimes ejeiSled 

 from the crater at the top, and fometimes from the fides of 

 the mountain, through lateral openings ; but always from an 

 elevation more than fifteen thoufand feet above the level of 

 the fea. M. Humboldt has given the name of plnelodus 

 cyclopum to this fpecies of fi(h. Some of them are found 

 living in the rivers on the fides of the mountains, and in all 

 probability they exift in fubterranean lakes, the fides of 

 which are broken down during violent commotions, or 

 melted by heat : hence the water finds its way to the crater, 

 and is ejcfted with other materials. From this accefs of 

 water, the mud or flime thrown out, called by the Indians 

 moya, is probably formed. 



In many inftances, however, the torrents of water which 

 iftue from volcanoes arife from the rapid thawing of the 

 fnow on the fummk. According to Humboldt, the colollal 

 volcanic cones in the Andes, covered with fnow, have be- 

 come fo hot in a fingle night as to melt the whole of the 

 fnow, and occafion the moil cxtcnfive and fatal inundations. 

 Torrents of water in"ued from Etna, in the eruption of 

 1755 ; but, according to Ferrara, ihey did not flow out of 

 the crater, but from the fnow and ice on the (urfacc fud- 

 denly thawed by the lava. A mafs of this ice, partially 

 melted by the lava, left a pile in the midft ft.iiiding like a 

 fuperb palace of cryilal. 



It is only by obfcrvations made in or near the crater, 

 wlien a volcano is in a quicfcent ftate, that we can gain any 

 knowledge of the faline or inflammable matter, which may 

 cither have fcrvcd as fuel to the volcano, or have been pro- 

 duced by the eruption, or been fubfcquently fublimcd. Of 

 thefe we (lull fpeak more particularly, in deicribing Folcanic 

 Produiii, infra. The rapidity and extent of a cnrrcnt of 

 3 K 2 lava 



