project, next spring, of passing some days at Puzzole, and of dissecting this mountain, taking its measures, and making drawings of its stratas; for, I perceive, it is composed of stratas, like Mount Vesuvius, but without lavas. As this mountain is so undoubtedly formed intirely from a plain, I should think my project may give light into the formation of many other mountains, that are at present thought to have been original, and are certainly not so, if their strata correspond with those of the Montagno Nuovo. I should be glad to know whether you think this project of mine will be useful; and, if you do, the result of my observations may be the subject of another letter[16]. I cannot have a greater pleasure than to employ my leisure hours in what may be of some little use to mankind; and my lot has carried me into a country, which affords an ample field for observation. Upon the whole, if I was to establish a system, it would be, that _Mountains are produced by Volcanos, and not Volcanos by Mountains_. I fear I have tired you; but the subject of Volcanos is so favourite a one with me, that it has led me on I know not how: I shall only add, that Vesuvius is quiet at present, though very hot at top, where there is a deposition of boiling sulphur. The lava that ran in the Fossa Grande during the last eruption, and is at least two hundred feet thick, is not yet cool; a stick, put into its crevices, takes fire immediately. On the sides of the crevices are fine crystalline salts: as they are the pure salts, which exhale from the lava that has no communication with the interiour of the mountain, they may perhaps indicate the composition of the lava. I have done. Let me only thank you for the kind offers and expressions in your letter, and for the care you have had in setting off my present to the Museum to the best advantage; of which I have been told from many quarters. I am, SIR, Your most obedient humble servant, W. HAMILTON. LETTER IV. To MATHEW MATY, M. D. Secretary to the Royal SOCIETY. An Account of a Journey to MOUNT ETNA. "Artificis naturae ingens opus aspice, nulla "Tu tanta humanis rebus spectacula cernes." P. CORNELII SEVERI _AEtna_. Naples, Oct. 17, 1769. SIR, Encouraged by the assurances you give me, in your last obliging letter of the 15th of June, that any new communication upon the subject of Volcano's would be received with satisfaction by the Royal Society; I venture to send you the following account of my late observations upon Mount Etna, which you are at liberty to lay before our respectable Society, should you think it worth its notice. [See Plate IV.] [Illustration: _Plate IV._ A View of MOUNT AETNA from Taormina.]