[3] In the subsequent eruptions of Vesuvius, I have constantly remarked something of the same nature, as appears in my account of the great eruption of 1767. I have found the same remark in many accounts of former eruptions of Vesuvius: in the very curious one of the formation of a new mountain near Puzzole, in 1538, (as may be seen in my letter to Dr. Maty, Oct. 16, 1770[46],) the same observation is made. This phaenomenon, is well worthy of a curious inquiry, which might give some light into the theory of the earth, of which, I believe, we are very ignorant. [4] I am convinced, that it might be very practicable to divert the course of a lava when in this state, by preparing a new bed for it, as is practised with rivers. I was mentioning this idea at Catania in Sicily, when I was assured, that it had been done with success during the great eruption of Etna, in 1669; that the lava was directing its course towards the walls of Catania, and advancing slowly like the abovementioned, when they prepared a channel for it round the walls of the town, and turned it into the sea; that a succession of men, covered with sheep-skins wetted, were employed to cut through the tough flanks of the lava, till they made a passage for that in the centre (which was in perfect fusion) to disgorge itself into the channel prepared for it. A book I have since met with gives the same account of this curious operation; it is intituled, _Relatione del nuovo incendio fatto da Mongibello 1669. Messina, Giuseppe Bisagni, 1670_. His Sicilian Majesty's palace at Portici, and the valuable collection of antiquities that have been recovered from beneath the destructive lava's of Vesuvius, are in imminent danger of being overwhelmed again by the next that shall take its course that way; whereas, by taking a level, cutting away and raising ground, as occasion might require, the palace and museum would, in all probability, be insured, at least against one eruption; and, indeed, I once took the liberty of communicating this idea to the King of Naples, who seemed to approve of it. [5] The late Lord Morton was pleased to give these specimens to Dr. Morris, who has made several chemical experiments on them, the result of which will be communicated to the Royal Society.