the valley is at this instant going on by waste precisely the same as they do in as they do in every other valley in the world. But though these dikes are witnesses of the waste, they are by no means measures of it; for they are not only equally exposed with their softer neighbours to disintegrating causes, but, from their projection, they are infinitely more exposed to these disintegrating causes. The head of every valley on a steep hill side forms, and must form, an amphitheatre, surrounded on three sides with' banks, if not precipices, the loftiest being at the upper end, and the height gradually diminishing on both sides.' Lyell says this of the Val del Pove, as if it was extraordinary, and peculiar to that valley. But if it were granted that this valley were formed by subsidence, is Lyell going to form all the other valleys of Etna by subsidence? or, if not, how have they been formed, except by the wash of rain? since they have confessedly never been under the sea. Lyell, indeed, says that running water in general exerts no power on Etna, the rain which falls being immediately imbibed by the porous lavas; so that, vast as is the mountain, it feeds only a few small rivulets, and these even are dry throughout the greater portion of the year. The enormous were both overwhelmed by these floods of mud, as in modern times were St. Sebastian and Massa, so suddenly as to suffocate seven persons. 'It will, therefore, happen very frequently, that towards the base of a volcanic cone alternations will be found of lava, alluvium, and showers of ashes.' Herculaneum is covered not only by showers of ashes, but by alluviums and streams of lava,' 'to a depth of nowhere less than 70, and in many places of 112 feet.' Lyell says of Torre del Greco : 'It seems probable that the destruction of three thousand of its inhabitants in 1631, which some accounts attribute to boiling water, was principally due to one of those alluvial floods which we before mentioned.' But alluvium is not deposited anywhere without a corresponding denudation somewhere. CHAPTER VII. LYELL ON THE VALLEYS OF CALABRIA. LYELL'S PRINCIPLES THE WORK OF THE AGE, BUT IT HAS LYELL writes of the earlier geologists' that they were singularly unconscious of the amount of their ignorance.' With regard to the formation of valleys, I should apply the words of this illustrious author to himself. And I should consider myself sufficiently illustrious, if my exertions could induce him to erase the one spot Lyell's 'Prin ciples' the work of the age, but it has from the great work of this age.' If not, the In his account of the formation of the valleys of Calabria, Lyell is as completely in contradiction as usual to his own submarine theory in particular, and to his four (or five) theories in general. Indeed, I think that he should here be credited with a sixth theory; for he here joins Lyell's sixth theory of the formation of valleys. fire and water in a most unholy alliance against how 6 6 distinct from their mode of Chapter xxix., 'Principles,' earthquakes contribute to the formation of valleys.' But his earthquakes in Calabria are no longer mathematical earthquakes' like those of the Weald. He does not crack out 'great fissures,' forming a rectangular intersection of geodesic lines,' like Humboldt, or fractures, 'longitudinal and transverse,' like Messrs. Martin and Hopkins. He makes his regular approaches, indeed; but on a system quite different from that employed in the Weald. He saps with water, and then springs his subterranean mine. With the Mediterranean on one side, and the Adriatic on the other, he surely throws away a chance for the employment of his own submarine plan. And with the crest of the Apennines between these two seas, what an inexhaustible field for fissures, cracks, and portages! But, no; earthquakes and the erosion theory become the sole and sovereign specific for valley-making here. When taken to be well shaken; that is, when water has undermined the cliff from below, an earthquake is to shake it down from above. The plan would be no great improvement, how ever. In 1783, 60,000 Calabrians fell wretched victims to one earthquake.* And if Providence were to be so improvident as to allow Lyell to carry out his plan as a system, the consequences would be as disastrous to the land as to its unfortunate inhabitants; for instead of gently sloping hill and dale, we should have a chaos intersected by clefts inclosed by cliffs. Lyell says (p. 466), that the formation of valleys by running water can never be understood if we consider the question independently of the agency of earthquakes. It must not be imagined that rivers only begin to act when a country is already elevated far above the level of the sea; for their action must of necessity be most powerful while land is rising or sinking by successive movements.' Again he talks of 'that peculiar removing force *The great igneous authority, Humboldt, repeats the ancient vulgar error, that volcanoes are safety-valves against earthquakes. The Calabrians,-oh fortunati nimium ! -are nearly surrounded by safety-valves-Vesuvius, Etna, Stromboli, and another in the Lipari Isles. Humboldt quotes Strabo for the fact that Sicily was much more shaken by earthquakes before it was divided from Italy! and before Etna was a volcano ! The modern earthquake referred to above, disregarding these ancient facts, not only desolated Messina at the foot of Strabo's safety-valve, but destroyed the aged Prince of Scilla, with 1430 of his people, who had taken to their fishing-boats in the hope of safety; and Humboldt says '60,000 were destroyed in Sicily, in 1693,' in spite of their Etna, their Stromboli, and their separation from Italy. |