The last hypothesis, or that which regards .Etna as the accumulated effect or successive eruptions, has been more generally received than the others. Indeed we know from observation, and the most authentic records, that by many of the great eruptions, new hills have been produced ; and that the greater number of the conical mounts which diversify the surface of Etna, bear une quivocal marks of the same origin. It is not without reason, therefore, that sonic have been !cc( to regard Alma, not as a single volcano, but as an assemblage of volcanic hills. M. Hotted, in his Voyage Pit torenue. states several arguments in support of this opinion. He indeed asserts, that !Etna is composed entirely of ma rine depositions, and the matter discharged from the volcano in its different eruptions. He informs us, that the base of the mountain consists of alternate lavers of lava and marine substances, successively deposited upon one another, and reaching to an unknown depth. These alternate layers, according to this author, must descend to the level of the stratum of lava which was discharged by the first eruption. The last layer deposited by the sea is a range of calcareous eminences of considerable height, placed on a basis of lava. Beneath this there is another stratum of sea pebbles, rounded by their mutual attraction. This again lies upon a yellow rock, consist ing of what is usually called indurated sand, over which the river Sim eto flows.
Much, however, is yet to he learned respecting the structure of .,Etna. It is to be hoped, that ere long, some disciple of the German school, less eager to form theo ries than to discover facts, will deem this mountain wor thy of particular investigation.
The facts brought to light in examining the structure of -Etna, have led to a discussion respecting its antiqui ty, which being intimately connected with our present subject, we must not wholly overlook. This question, in itself perhaps of no great importance, has acquired considerable interest from the attempts made by some to employ the conclusions drawn from it, as an aru meet against the divine origin of the Scriptures. The general fact has already been alluded to, viz. that in dif ferent parts of !Etna, layers of lava are found alternating with beds of vegetable mould ; but Canon Recupero has furnished us with a particular fact of this kind. In the neighbourhood of Jaci, he informs us, that in digging a pit, he discovered no less than seven distinct layers of lava, each of which was covered with a bed of rich vege table earth. If by any means, therefore, we can discover the number of years required to convert lava into mould, or to cover it with a bed of vegetable earth of a certain thickness, it seems but fair to conclude, upon the evi dence of this fact of Recupero's, that the mountain has existed at least seven times that period. Now Recupero himself furnishes us with the very step which is want ing to complete this argument. He points out a bed of lava, which he conceives to have been deposited about the time of the second Punic war, so thinly covered with soil, as to be still unfit for producing either corn or vines.
Ila period of 2000 years, thercforc,be required for con verting lava into soil, 14,0p0 must have elapsed since the formation of the lowest bed of the pit at Sad ; and consequently, the mountain must have existed at a pe riod still more remote.
Before inquiring how far this reasoning is correct, it may be proper to observe, that, admitting the argument respecting the great antiquity of the world to be conclu sive, it does not follow that the Mosaic account is either false or inconsistent with facts. Muses professes to give an account of the history of mankind from the earliest period, and describes the manner in which the earth was prepared for his habitation ; but he no where pre tends to give the date of its formation. The earth, there fore, may have existed, and undergone various revolu tions, previous to the period at which the Scripture nar ration commences.
But lest this mode of removing the difficulty should appear to some of our readers not altogether satisfac tory, we shall now examine the argument itself. Its whole force seems to depend upon two circumstances ; upon the accuracy of the fact respecting the bed of lava which is said to have flowed from the mountain in the time of the second Punic war ; and upon the correctness of the general assumption, that all lavas require the same number of years to fit them for supporting vegeta ble life. With regard to the first point, we have no means of ascertaining what degree of credit is due to the opinion of Recupero. lie, indeed, speaks of it as a matter clearly made out, but does not inform us from what principles he derived his conclusion.
But admitting that this particular bed of lava did flow from the mountain about 2000 years ago, and that it is still scarcely fit for the purposes of vegetable life, does it follow that all lavas are equally refractory ? If we were entitled to decide upon the qualities of lava, from what happens in the parallel case of iron slag, we might with out hesitation affirm, that lavas become fertile at very different periods, according to the nature of the sub stances from which they are derived, the consistency of their parts, the position of the bed, and their degree of exposure to those agents which produce a disintegration of tneir parts. But fortunately on this subject we are not under the necessity of having recourse to the doubt ful argument of analogy. It is a fact well ascertained, that volcanic ashes and pumice vegetate much sooner than compact solid lava. But even lavas, apparently in similar circumstances, are covered with vegetable mould at very different periods. Chevalier Gioeni in forms us, that he found, in 1787, lavas which had been projected only 21 years before that period, in a state of vegetation ; while others, much more ancient, remained barren.