-a; T N 



"iE T N 



tTieir being the produiTtions of fire. They bear unequivocal 

 marks of the cfcfts of this Jeftniftire agent in an accumu- 

 lation of lava, fcorise and volcanic fand. AVhellicr the 

 origin of thefe mouniains is to be traced to the cxpanfive 

 effort of the ignited matter contained within the great abyfs 

 of JEtm, and whicli, incapable of afcending to the upper 

 crater, burfls foi-th at the fides ; or whether they are to be 

 afcribed to particular conflagrations and eruptions, wliich 

 have no communication with the imnienfe furnace within 

 the crater, has been a fubjeft of inquiry and difcuflion. 

 The former alternative has been generally allowed ; and it 

 mull be acknowledged that this is ircquently the fa£t. In- 

 ftances, however, may be cited, which afford llrong reafons 

 for believing that the production of the lateral mountains is 

 owing- to partial eruptions, wliich have no communication 

 with the principal crater. Of this ki.id is Monte Rojfj, of 

 which an account will be given in the fequel of this article. 

 Kir W. Hamilton reckons 44 mountains of this kind on 

 the fide of Catania, with their dillintt craters, moll of 

 which are now in a ftate of fertility. 



From the confideration of the conllituent parts of ^tna, 

 and the mode of its formation, we fliall proceed to ftate its 

 dtmaifwns. Thcfe have not yet been fatisfaftorily afcertained. 

 Its ilupendous height and bulk were noticed lb long ago as 

 the time of Pindar, more than 435 years before Cluift, in a 

 p'iiTage which we fliall cite in the progrefs of our account. 

 He reprefents it not only as the eternal abode of fnows, but 

 as the pillar of heaven. The ancients in general, as well as 

 tlie moderns, have been accutlomed to confider y£tna as one 

 of the higheft mountains on the globe. There are many 

 paffages in their writings, fays Mr. Brydone, that (hew this ; 

 though, perhaps, none more ftronglv than their making 

 Deucalion and Pyrrha take refuge on the top of this mountain, 

 in order to fave themfelves from the univerfal deluge. Theie 

 ideas, however, appear to be very erroneous ; for Sir George 

 Shuckburgh obferves, (Phil. Tranf. vol. Ixvii. p. 595.) that 

 Vefuvius, placed upon Mount Atna, would not be equal to 

 the height of Mont Blanc. The accounts of thofe who 

 have vifited TEtna in later times have been very various. 

 The following meafures have been given by different 

 authors. 



Height above the furface of the fea, T Faujasde S.Fond in 



1 0,0 ■56 feet. 



> his Volcans du Vi- 



Kircher. 



Italian Mathemati- 

 cians. 

 Brydone. 



ccupero. 



Circumference at the bafe, 180 miles. J varais. 

 Height, 4000 French toifes. 



3 miles 264 paces. 



4 6 and 8 miles. 



1 2000 feet — — 



2500 toifes ; circumference 



1R3 miles. 



'95° toifes ; diameter 



'^o miles. 



3000 fathoms; circumference"! BufFon's Nat. Flift. 



60 leagues ; and fuperlieles '- by Smellie, v. ix. 

 300 fquare leagues. J 14^, 



— — — funimit above the Medilerva-] 

 ncan 10954 feet. I 



circumference of the vilible | Sir George Shuck- 

 horizon on the top of Mount \ burgh, Phil.Tranf. 



V 



( Mentelle Gcogr. 

 ' Comp. 



yTtna, 6' being allowed for 

 rcfradlion, is 1093 Enghfh 

 miles. 



vol. Ixvii. p. 59J. 



Other,-, make its height only 2000 toifes, and its fuj^erficies 

 3C0 Iquare miles. By the following heights of the ther- 

 mometer and barometer, at different nations, extrafted from 

 Brydone's Tour, v. i. p. 211, their refpedive elevations 



might be afcertained, if the altitudes by ihc inftruinents 

 were accurately taken. 



Height of Fahrenheit's Thermometer. 

 At Catania, May 26, at noon, . . . ^(J 



Ditto, 27, at 5 in the morning - 72 



At Niciiofi, 12 miles up the mountain, at noon 73 



At the cave, called Spelonca del Capriole, in flic 



feeoiid region, where there was a confiderable 



quantity of fnow, at 7 at night - - 6f 



In the fame cave, at half an hour paft 11 - 52 



At the Torre del Philofopho, in the third region, at 



three in the morning ... 34^ 



At the foot of the crater of ILXxa. - - 33 



About half way up the crater - - 29 



On tlie fummit of ^tna, a little before fun-rife 27 



Height of the Barometer in inches and lines. 

 At the fea-fide at Catania - - 29.8I 



At the village of Piedmonti, in the firfl region of 



jEtna ... 27.8 



At Nieolofi, ditto - - 27. li 



At the Caflagno di Cento Cavalli, in the fecond 



region ... 24.1 



At the Torre del Philofopho, in the third region 20.5 



At the foot of the crater - - 20.4' 



Within about 300 yards of the fummit - 19.6-2 



At the fummit of ^tna, where the wind prevented 



an exaft obfervation, fuppofed to be - 19.4 



M. Houel (uhi fupra) ilates the circumference of the 

 bafe at 40 miles ; and though he had no opportunity of 

 meafuring the altitude, he obferves, that it had been done 

 by M. de Sauffure, who found it to be 10,036 feet, or, as we 

 learn from Senebier, 10,963 Englifh feet. This was afcer- 

 tained on the 5th of June, 1773, at 20' after feven in the 

 morning. The height of the barometer, on the mod ele- 

 vated part, at the brink of the crater, was 18 inches 

 I if lines; whigh, by the neceffai-^' coireftions, is reduced 

 to 18 inches io4-| lines. At the fame time, the mercuiy at 

 Catania, placed only one foot above the level of the fea, 

 flood at 28 inches Z-^ lines, which muil be reduced to 

 28 inches l^- line, on account of the requifitc correftions 

 for the thermometer. 



Some have fuppofed, that volcanic mountains always in- 

 creafe in height by tli£ produfts of fucceffive eruptions, till 

 they are extinguifhed. However, it is generally conceived 

 that the height and bulk of ^tna are much the fame now 

 as they were in former times. The dilapidations, occafioned 

 by the falling in, and abforption of the fummit, have pro- 

 duced, for time immemorial, no lenfible diminution ; as the 

 lofTes refulting from fome eruptions* are repaired bv ethers 

 which fucceed. In proof of this, it is alledged, that if 

 any confiderable decreafe of the mountain had taken place, 

 ice and fnow would not have continued, in a climate fo mild, 

 to envelope the top of the mountain, as they now do, even 

 during the greatefl heats of fummer. On the contrary, it is 

 a vei-y old opinion (vide Seneca, Epifl. 179, and iElian Var. 

 Hill. 1. viii. c. xi. tom. i. p. 548.) and adopted by M. 

 Houel, that jEtna is in a ftate of decay and diminution, fo 

 that it cannot be obferved at fo great a diflance as formerly. 

 It is full of excavations ; and he confiders the torrents of 

 lava, which overfpread its fides from time to time, as infuf- 

 ficient for repairing the v/alle occafioned by rains, rivulets, 

 and torrents flowing down from the fummit. Hence he 

 concludes that, unkfs the eruptions become more frequent 

 than they have been for fome time paft, the height of the 

 mountain will be gradually reduced to that of the fun-ound- 

 ing beds of lava. Over the fides of y£tna there arc fcat- 

 T t 2 icred 



