These, as well as I can recollect, are all the observations that I made with respect to Volcanos, in may late curious tour of Sicily; and I shall be very happy should the communication of them afford you, or any of our countrymen (lovers of natural history) satisfaction or entertainment. I am, SIR, With great regard and esteem, Your most obedient humble servant, W. HAMILTON. LETTER V. To MATHEW MATY, M. D. Secretary to the Royal SOCIETY. REMARKS upon the NATURE of the SOIL of NAPLES, and its Neighbourhood. "Mille miracula movet saciemque mutat locis, et defert montes, subrigit plana, valles extuberat novas, in profundo insulas eregit." SENECA, De Terra-motu. Naples, Oct. 16, 1770. SIR, According to your desire, I lose no time in sending you such further remarks as I have been making with some diligence, for six years past, in the compass of twenty miles, or more, round this capital. By accompanying these remarks with a map of the country I describe [Plate VI.], and with the specimens of different matters that compose the most remarkable spots of it, I do not doubt but that I shall convince you, as I am myself convinced, that the whole circuit (so far as I have examined) within the boundaries marked in the map is wholly and totally the production of subterraneous fires; and that most probably the sea formerly reached the mountains that lie behind Capua and Caserta, and are a continuation of the Appenines. If I may be allowed to compare small things with great, I imagine the subterraneous fires to have worked in this country, under the bottom of the sea, as moles in a field, throwing up here and there a hillock; and that the matter thrown out of some of these hillocks, formed into settled Volcanos, filling up the space between one and the other, has composed this part of the continent, and many of the islands adjoining. From the observations I have made upon Mount Etna, Vesuvius, and its neighbourhood, I dare say, that, after a careful examination, most mountains, that are or have been Volcanos, would be found to owe their existence to subterraneous fire; the direct reverse of what I find the commonly received opinion.