Al T N 



JET N 



D'Orvillo, wlio afccndcd iEtna in 1727. I'cmaikcd two cvn- 

 tJrs, (VIC larger than the other, and in ciicumfeiciice ("orae- 

 vhat more than four miles, from xvhieh idutd clouds of 

 i'mokc and reddilh flames. On looking into tliis crater, he 

 and his companions were unable to dilcern the holtoni on 

 account of the llames and fmoke. They only obfcrved that 

 a conical hill, formed of lava, rofe in the middle of , the cra- 

 ter, the top of which thty eftimatcd to be 60 feet below 

 them ; and as they were ]irobably able to fee about C)0 teet 

 lower, they conjeftured that ihc circuit of tiiis hill uiight 

 he f;om Coo to ;(oo feet, 



M. Hoiiel, whofe account of tliif mountain was publilaed in 

 r7S2, and who made a drawin<r of the crater, reprefents its 

 environ; asconfillir-.gof three emmenees, forming an equilatend 

 triangle, though when viewed at a ilillancc, only two of them 

 can be feen ; for which reafon the Sicilians have denominated 

 the mountain /lironis, or double horned. The filuation of the 

 principal mouth is in the midll of tliefe three eminences, its 

 diameter was only about 6q feet; but it was io Idled with 

 fmoke that nothing remarkable coidd be difcovered. This 

 author obferves, that the cone is not exactly m the middle of 

 the plain, but that it hes iomewhat more to the uoith than 

 the foulh. Evciy obfervation, therefore, tends to evince 

 the inconftancy of the internal configuration and drmenfions 

 of this volcano. Befide the changes which have taken jilace 

 on the fummit of jEtna, with rtfpeft to the number, form 

 and fi7.e of its craters, Fazello and I'.Drelli defcribe another 

 alteration occafioned by the falling in and abforption of the 

 extreme fummit of the mountain within its crater. The 

 former author relates, that in his time there arofe in the 

 moKth of the crater a little hill, ifolated on eveiy fide, which 

 formed the vertex of the mountain, and which, in a terrible 

 eruption, fell into the gulf, and thus eidarged the crater and 

 diminifhed the height of the mountain. The hill itfelf had 

 been produced by a former eruption in 1444., Borelli like- 

 wife informs us, that in the conflagration ot 1669 the fum- 

 mit of jEtna which rofe, like a tov/er, to a great height 

 above the part which is level, was fwallowed up in the deep 

 gulf. Strabo (tom. i. p. 420, &c.) relying on the account 

 of thofe who had vifited TEtna in his time, defcribes the 

 fummit as a level plain, about 20 lladia in circumference, 

 furrouuded by a brow, or ridge, of the height of a wall ; 

 and he adds, that in the middle of the plain arofe a fmoky 

 hill, the fmoke of which afcended in a dircil line to the 

 height of 20 fett. Solinus (cap. 1 1 ) informs us, that there 

 were two craters, from which the vapours "ifrued. Cardinal 

 Bembo likewife fua\id two eiaters, one higher than the other, 

 and about as far diltant as a Hone might be tlu'own from a 

 fling. The extreme violence of the wind and tlie exhaled 

 fumes prevented his approaching the upper crater ; but 

 he defcribes it from the information of others, as fituatcd on 

 the liighell part of the fummit ot ^Etna, about three miles 

 in circumference, formed like a funnel, and having in its 

 middle a fpacioiu cavity. In the time of Fa/.cUo, who 

 vilited iEtna alter Bembo, there was onlv one crater about 

 four miles in circumference. Its form was that of a funnel ; 

 it emitted fire and thick fmoke ; and a fubterraneous noife 

 was heard, which rcfeir.bled the boiling «f an immenfe cal- 

 dron on a very lierce fire. 



As for the dilferencc that occurred with regard to the 

 ajipearancc of the fmoke, noticed by difterenl writers, fome 

 of whom reprefent it as nfliiug down the fides of the moun- 

 tain, and others, as aicending perpendicularly to a-great 

 height, and afterwards falling, like white flowers on the top 

 of the mountain ; it was owing, without (h)ubt, not only 

 to the diflcrcnt deniity of the air on iEtna at different times, 

 but alfo to the diverfity of the fmoke, v/hich wonld fimie- 

 times be lighter and fometiines heavier than the air itfelf,- 



Vor. I. 



accord mg to the qualities of the fubflanrcs from which it 

 is prod deed. 



The effects o.'' the air at the fummit of ALtns, recited by 

 different writers, have alfo been vsiy diffeient. Some havi; 

 complained of the difficulty of relpiration v.'hich they ex- 

 perienced, whilll others felt no l.ich dilhcully, and aflcrt • 

 that rcfpiralion is performed with equal eafe on the top of 

 the mountain, as in the country below. It ajjpears fron» 

 the obf rvations of M. oauflure in liij travels on the Alps, 

 that, allhoigh at the height of M'. unt Blanc, about 2450* 

 poles above the level of the fea, a codlderable difiiculty of 

 relpiration was occafioned by the r^rcfacflon of the air, no 

 fiich inconveftience was experienced at the leis elevation of 

 1900 poles. The height of /Una being lefs than the laft 

 nicafurc, it is natural to infer th.rvl 'lie relpiration of many 

 perfons wuuid not be incommoded, '. hilll the contraiy hap- 

 pens to otiiers, according to the diiferent ftre;;gth and habit 

 of body of different individuals. The oblerved difference 

 of the barom-ter indicated in tliefc varioiu circumflances a 

 coniiderable dilTercnee in the weight and rarity of the air. 



Spallanzani obferves, that iiitna has at all times been 

 very deficient in fprings ; and when he vifitcd this moup.- 

 tain, water was fo extremely icarce, that a fiiigle drop of 

 rain had not fallen for nine months. As the rain water which 

 the peafants, who inhabit different parts of it, had coUcCled 

 in ciflerns was exhaulled, th'-y were obhged to go in fearch 

 of it to thofe parts of the mountain at coniiderable diftan- 

 ces, where a fcanty fpring might ilill be found. This 

 author has obfei-ved a fimilar fcarcity of fpnngs in the 

 jEolian or Lipari iflands ; and he apprehends, that other 

 volcanic countries are fubjecf to the fame inconvenience. 

 Tile rains, he fays, which defcend on mountnins of this 

 kind, fall on tufas or fcoriE, in which they fink deep and 

 do not again appear, becaufe tliey meet with no argillaceous 

 or itony ilrata capable of detaining them ; whei-eas fuch 

 flrata are frequent in other mountains, and produce nuineroi;-; 

 fprings, as we find to be the cafe in the Alps and Ap;;::- 

 uines. When the rains fall on compaft and folid lavas, 

 they do not link into them, but run down their declivities, 

 forming rivers and torrents in the rainy feafon, and not true 

 fprings. In feveral parts of /litna, and efpeciallv near the 

 GrnHa delle Capic, he obfencd large furrows hollowed in 

 the lavas, by the action of the rain water. Other writers, 

 however, have given a very different account. They ilate, 

 that vEtna abounds with fountains and v>'ith rivers of con- 

 fiderable magnitude." See Acis and Alcantara. Mr. 

 Brydone informs us, that there are feveral periodical fprings 

 on iEtiui, that flov>' during the day and Hop at night, 

 which he attributes to the alternate melting and freezing of 

 the fnow. There are alfo poifonous fprin';-s, which emit a 

 very noxious vapour ; and others which afford fine fait ; and 

 others again, whole water ierves for dying particular co- 

 lours. On the north fide of the fnowy region, there are feveral 

 fmall lakes which never frec/.e. M. Hmu-l eilimates the 

 quantity of water which flows down the lides of the moun- 

 tain to be fuch, that if it were collected it would fill the 

 channel of a river 36 feet broad and fix feet deep ; and he 

 adds, that llreams of water are feen to ilfue at all d'fferent 

 degrees of height from the bafe to the lummit of the 

 mountain ; and that thefe continue to flow even during the 

 droucrht of fummer. The fupply of theie ftre:ims, he 

 thinks, cannot be accounted for by the water depofited by 

 the clouds, iior by the melting of the fnow ; but the fourcc 

 of it inuil be more regular and permanent. This he c n- 

 ceives to be the evajjoration of thofe aqueous particles th it 

 arife from the conllant ebullition at the bottom of the vol- 

 canic focus, and which, in his opinion, are necelfaiy to the 

 fubliftence of volcanoes. Thefc vapours, iffuing from the 

 U u great 



