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192 which he perceives among them, until from new observations, he is obliged to change his opinions, and give a new arrangement to the same facts.

Among the modern systems of geology, there are two as old as the study of nature, which appear to dispute for precedence, while the minor systems have reference, and can easily be reduced to them. One is, that the earth was originally in a state of igneous fusion, which is gradually cooling, and becoming covered with water. The other, that it was originally water, which, by absorption, is gradually forming a solid mass. These systems seek to explain every geological fact and natural phenomenon on different principles. But facts multiplying with observation, and being incapable of explanation, if we adhere exclusively to either system, what can be more natural than a mutual toleration of opinion? If a metaphysical disquisition would be considered fantastical, unless its principles agreed with facts, how should we regard a physical disquisition which should treat of colours, sounds, heat, cold, the motions of bodies, &c, without making use of sense, instruments, and various experiments? By the aid of observation and palpable facts, naturalists and geographers enumerate upwards of 300 active volcanoes upon our globe, the names and situation of which it is superfluous to mention; and according to the more or less vast extension of territory over which they exercise their sphere of activity, five volcanic zones have been defined; the accurate reasoning of Ferdinando of Lucca upon this subject is well known to the scientific world.

The kingdom of the Two Sicilies, that is to say, Vesuvius and Etna, (not to speak of other volcanic regions, and Vulture, which appears extinct, and perhaps is not,) forms a portion of one of these zones. The existence of these fire mouths, scattered for the most part at great distances over the surface of the globe, leads us reasonably to conclude, that a great fire exists in the interior, or, to speak with the Vulcanists, that the nucleus is in a state of incandescence, or that it has not yet cooled down from its primeval state of igneous fusion. To this we must add, that by the repeated experiments made by philosophers, the thermometrical temperature beneath the strata is found invariable, and has continued so for