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Show 434 .EXCAVATION OF VALLEYS. combined with the motion of the earthquake, and the enveloping of land animals, together with many other facts mentioned in the Calabrian account, cannot but excite in the mind of every geologist a strong desire to become more acquainted with the changes now in progress in those vast regions of the globe which are habitually devastated by earthquakes. To our extreme ignorance of this important class of phenomena we may probably refer the obscurity of many of the appearances of superficial alluvions throughout the greater part of Europe, as well as the diversity of opinion relating to them, and the extravagant theories which have passed current. The portion of the Calabrian valleys formed within the last three thousand years, must, undoubtedly, be inconsiderable in amount, compared to that previously formed, just as the lavas which have flowed from Etna since the historical era constitute but a small proportion of the whole cone. But as a continued series of such eruptions as man has witnessed would reproduce another cone like Etna, so a sufficient number of earthquakes like that of 1783 would enable torrents and rivers to re-excavate all the Calabrian valleys if they were now to be entirely obliterated. It must be evident that more change is effected in two centuries in the width and depth of the valleys of that region, than in many thousand years in a country as undisturbed by earthquakes as Great Britain. For the same reason, therefore, that he who desires to comprehend the volcanic phenomena of Central Franee will repair to Vesuvius, Etna, or Hecla, so they who aspire · to explain the mode in which valleys are formed must visit countries where earthquakes are of frequent occurrence. For we may be assured, that the power which uplifted our more ancient tertiary strata of marine origin to more than a thousand feet above the level of the sea, co-operated at some former epoch with the force of rivers in the removal of large portions of rock and soil, just as the eleva tory power which has upraised newer strata to the height of several thousand feet in the south of Italy has caused those formations to be already intersected by deep valleys and ravines. He who studies the hydrographical basin of the Thames, and compares its present state with its condition when it was a Roman province, may have good reason to declare that if that EXCAVATION OF VALLEYS, 435 .r ivetr' and itds trib. utarI' es h a d sm. ce thei. r origin been always as mac 1ve, an as Impote t h not even in millions o~ as t ey are now' they could never, through which th fl !ears, ~ave excavated the valleys . ey ow · but, If l1e concludes ~ th premises, that the v 11 · . . J.rom ese · a eys 111 this hasm were not formed b ordmary causes, he reasons like one who h . ~ d 1~ y t h. h ~ ' avmg J.OUn a so J.a-ara w IC J.Or many centuries has th . h d rown out nothmg more t an vapour an a few handfuls of sand and . . ~ h ] f scorue, In1ers t at a o ty cone, composed of successive streams of 1 d . tions, can no longer be produced by volcan·I c agenacvya. an eJeC- 2 F 2 |