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Show 324 VOLCANIC REGIONS. coast *-a fact which is the more interesting, because a line drawn through the Grecian archipelago, the volcanic region of Southern Italy, Sicily, Southern Spain, and Portugal, will, if prolonged westward through the ocean, strike t~e volcanic group of the Azores, which has, therefore, in a1l probability, a submarine connexion with the European line. How far the isles of Madeira and the Canaries, in the former of which violent earthquakes, and in the latter great eruptions, frequently happen, may communicate beneath the waters with the same reo·ion 0 ' must for the present be mere matter of conjecture. Besides the continuous spaces of subterranean disturbance of which we have merely sketched the outline, there are other disconnected volcanic groups, of which the geographical extent is as yet very imperfectly known. Among these may be mentioned Iceland, which belongs, perhaps, to the same region as the volcano in Jan Mayen's Island, situated five degrees to the northeast. With these, also, part of the nearest coast of Greenland, which is sometimes shaken by earthquakes, may be connected. The island of Bourbon belongs to another theatre of volcanic action, of which Madagascar probably forms a part, if the alleged existence of burning volcanos in that island shall, on further examination, be substantiated. In following round the borders of the ocean to the north, we find the volcano of Gabel Tor, within the entrance of the Arabian Gulf. In the province of Cutch, in Bombay, and the adjoining districts of Hindostan, violent earthquakes repeatedly devastate an extensive territory. Respecting the volcanic system of Southern Europe, it may be observed, that there is a central tract where the greatest earthquakes prevail, in which rocks at·e shattered, mountains rent, the surface elevated or depressed, and cities laid in ruins. On each side of this line of greatest commotion, there are parallel bands of country, where the shocks are less violent. At a still greater distance (as in Northern Italy, for example, extending to the foot of the Alps), there are spaces where the shocks are much rarer and more feeble, yet possibly of sufficient force to cause, by continued repetition, some appreciable alteration in the external form of the earth's crust. Beyond these limits, again, all countries are liable to slight tremors at distant intervals of time, when some great crisis of subterranean movement agitates an adjoining volcanic region; but these may be consi- • Vl.'rneur, Journal des Vc.yages, vol, iv., p. lll. Hoff; vol. ii., P· 275. VOLCANIC REGIO~S. 325 dered as mere vibrations external crust of the gl b propagated mechanically through the distances throu()'h the a~ e, ;~ so~nds travel almost to indefinite England, Scotl~nd Nor~h . ; s of this kind have been felt in larly during the Lisbo ern hrance, and Germany-particu-n eart quake B t tl cannot, on this account b · u lese countries southern volcanic regi~n e supposed to constitute parts of the Orkney Isles can be con ~danyd more tha~ the Shetland and . l b st ere as belonO'mg t tl I c1rc e, ecause the sands ej t d f o 0 le celandic thither by the winds. ec e rom Hecla have been wafted We must also be careful to d. . . extinct and active volcanos Ishtmgmsh between lines of h . . ' even w ere they ap . t e same directiOn . for ancient d d pear to run m d · ~ ' an mo ern syste an mter1ere with each other AI. d . ms may cross that this is the case; so that .it is ~:; .,/, mdeed, w.e have proof but by reference to the spec' f y geographiCal position · les o organic bei 1 ' aquatic or terrestrial whose . . ngs a one, whether · ' remams occur 1 b d · With lavas, that we can clear] d' . . n e s mterstrati:fied volcanos of which no t' y Istmgmsh the relative age of I l erup IOns are record d H d Ata Y .b een known to civilized nati.O ns 1~ 0r ea s · sh ta Sou. thern meriCa, we should have h d ~ or a penod as yet we might have assured. a no record of eruptions in Ischia; flowed since the Medit ourselves t?at the lavas of that isle had t erranean was mhabited b th estacea now living in the Ne r y e species of it would not have b h apo ltan seas. 'Vith this assurance that isle in the m eden ras Ito i?clude the numerous vents of . . o ern vo came grou f C . Similar grounds we rna 1 . P o ampama. On marine lavas of the V ~ cd~sNs, Wit?ou~ l~uch hesitation, the sub-f b a I oto m SICily in tl d . 0 su tcrranean commot' f 1 . ' Ie mo ern circle a part. But the la IOfn,lo Ew uch Etna and Calabria form . vas o t 1e 'ugan h'll tm, although not wholl be d ean 1 s and the Vicen- Northern Italy must y t bon the range of earthquakes in volcanic system~ £ . }no e confounded with any existing with animals e~ti ~~~ w~;n, they flowed, the seas were inhabited whether in theM rd~ty Istlnct from those now known to live e 1 erranean or oth f ' we ~annot enter into a full d er parts o th~ globe. But subJects in the present 1 evelopment of our VIews on these co nsi' d eration of ch vo u.m e ' as they wou ld carry us into the to. the. times of hist~~ges In t?e earth's surface far anterior ex~htsively confine I y, to wluch our present examination . C, IS |
