[F] Earthquakes, though in distant regions, usually precede eruptions. The Earthquake of Melfi preceded the great Eruption of Etna in 1852; the Earthquake of Basilicata of December, 1857, terminated with the Eruption of 1858, which filled the Fossa Grande with lava; the Earthquakes of Calabria of 1867 and 1870 were the precursors of the Vesuvian conflagrations of 1868, 1871, 1872. A Volcano, also, in the Island of Java had a great eruption in the month of April, some days before the last conflagration of Vesuvius, as I learnt from a letter addressed to Signor Herzel, Swiss Consul at Palermo, communicated to me[7] by the astronomer, Signor Cacciatore.--_Palmieri._ [G] I have made a large collection of sublimates, which I purpose examining with the spectroscope, and I shall be able to place some at the disposal of experimentalists who may desire to pursue investigations of this kind. NOTES BY THE TRANSLATOR. [1] (P. 82, text). Professor Palmieri has not given any description in this Memoir of his seismograph--the instruments described being those only which have relation to atmospheric electricity. The following brief account of his seismograph will, therefore, form a not unsuitable complement to his Memoir. The instrument, in general terms, is of that class in which the wave movements are indicated by the displacement, relative or absolute, of columns of mercury in glass tubes. It is a self-recording instrument, composed of two distinct portions--one for record of horizontal, or rather of what are called undulatory shocks; the other for vertical shocks. In point of general principle, therefore, it is very similar to that proposed by me ("Transactions, Royal Irish Academy," in 1846), and in certain respects appears to me less advantageous than the latter. Some account of the Palmieri instrument, together with some critical remarks as to its action, may be found in my "Fourth Report on Earthquakes" ("Reports, British Association, 1858," pp. 75-81). The following description of the instrument is derived from "The Engineer," of 7th June, 1872, and the publishers have to thank the proprietors of that journal for permission to use the illustration, Plate 8.