In a piece of stratum, calcined from the outside of the Solfaterra, the form and texture of the pumice stones is very discernible. In several parts of the outside cone, this calcining operation is still carried on, by the exhalation of constant very hot and damp vapours, impregnated with salts, sulphur, alum, &c. Where the abovementioned vapours have not operated, the strata of pumice and erupted matter, that compose the cone of the Solfaterra, are like those of all the high grounds in its neighbourhood, which I suppose to have been thrown up likewise by explosion. I have seen here, half of a large piece of lava perfectly calcined, whilst the other half out of the reach of the vapours has been untouched; and in some pieces the centre seems to be already converted into true marble. The variegated specimens then, above described, are nothing more than pumice and erupted matter, after having been acted upon in this manner by the hot vapours; and if you consider the process, as I have traced it, from bitumen to pumice, and from pumice to marble, you will think with me, that it is difficult to determine the primitive state of the many wonderful productions we see in Nature. I found, in the _tufa_ of the mountain of Pausilipo, a fragment of lava: one side I polished, to shew it to be true lava; the other shews the signs of the _tufa_, with which it is incorporated. It has evidently been rounded by friction, and most probably by rolling in the sea. Is it not natural then to imagine that there must have been Volcanos near this spot, long before the formation of the mountain of Pausilipo? This little stone may perhaps raise in your mind such reflections as it did in mine, relative to the great changes our globe suffers, and the probability of its great antiquity. FOOTNOTES: [1] Having reflected since upon this circumstance, I rather believe that the weight of the atmosphere in bad weather, preventing the free dissipation of the smoke, and collecting it over the crater, gives it the appearance of being more considerable; whereas in fine weather the smoke is dispersed soon after its emission. It is, however, the common-received opinion at Naples (and from my own observation is, I believe, well founded), that when Vesuvius grumbles, bad weather is at hand. The sea of the Bay of Naples, being particularly agitated, and swelling some hours before the arrival of a storm, may very probably force itself into crevices, leading to the bowels of the Volcano, and, by causing a new fermentation, produce those explosions and grumblings. [2] These ashes destroy the leaves and fruit, and are greatly detrimental to vegetation for a year or two; but are certainly of great service to the land in general, and are among the principal causes of that very great fertility which is remarkable in the neighbourhood of Volcano's.