1, 1. The Fissures of the 26th of April. 2, 3. Small Hill thrown up on the morning of the 26th of April, from below which issued the great current of Lava. 4, 4, 4. The Mouths out of which the Lava issued. 5, 5. The larger Lava Stream, which passed near the Observatory by the Fossa della Vetrana. 6, 6. The other Lava Stream, which, after dividing from the last, took the direction of Resina. 7, 7. The Lava which ran down towards the Camaldoli. 8 & 9. The two Craters on the summit of the Cone. VIa. The Bifilar Electrometer of Signor Palmieri. (_Details._) VIIa. The assemblage of the Electroscopic Apparatus of Signor Palmieri, as arranged at the Vesuvian Observatory. VIII. Professor Palmieri's Seismographic Apparatus. [A] This small cone, as it appeared on the 1st April, is described and drawn in a Memoir of Professor von Rath, of the University of Bonn, on "Vesuvius on the 1st and 17th of April, 1871." [B] Eight young medical students perished beneath the lava, with others unknown by name. They were all youths of good promise; their names will be recorded on the marble monument to be erected near the Observatory. They are: Girolamo Pausini, Antonio and Maurizio Fraggiacomo, Francesco Binetti da Molfettu, Giuseppe Carbone da Bari, Francesco Spezzaferri da Trani, and Giovanni Busco da Casamassima and Vitangelo Poli. [C] If this enormous height of projection really means, that above the brim of the crater, it involves an initial velocity of projection of above 600 feet (British) per second. Observations of the height of ascent of volcanic blocks are always difficult and deceptive, and never free from error.--_Translator._ [D] Assuming these flashes to have emanated from somewhere within the cloudy volume of steam and dust called "the head of the pine-tree," this interval would indicate that the mean height of this cloudy volume itself was not more than about four thousand feet above the top of the cone; and, if so, that is not very far from the limit in height of projection of the dust and lapilli.--_Translator._ [E] COTUNUITE, chloride of lead, in white, lustrous, acicular crystals, of the trimetric system, easily scratched, Sp. gr., 5·238. TENORITE, peroxide of copper, in thin, hexagonal plates or scales, translucent when very thin, dark steel gray, of the cubic system; hard and lustrous. Sp. gr. about 5·950.--_Translator._