Part 15

11. The fumaroles at the summit of Vesuvius present even greater gradations, for they often emit carbonic acid or pure watery vapour.

12. Lead, which I first discovered in the fumaroles of the lavas of 1855, is a constant product of fumaroles which have a certain duration. It is often obtained as a distinct and crystallized chloride, and often is found in combination with other products.

13. Oxide of copper is also a constant and primary (primitivo) product of fumaroles. The chloride and sulphate of copper are formed from the oxide, directly contrary to general belief.

14. I do not think that the chloride of calcium, which I found on this occasion in almost all the deliquescent sublimations, is a product peculiar to this eruption only, in which alone, however, I found it. I was, therefore, induced to look for it in other sublimates, in which I might possibly have overlooked it, as, without doubt, my predecessors have done, owing to the deliquescence of the chloride of iron with which it was constantly combined. I think that this chloride, in accordance with the general law, is transformed into a sulphate--a transformation which readily occurs on Vesuvius.

15. Copious and well-crystallized sal ammoniac is only found on the fumaroles of those lavas which have covered cultivated or wooded ground.

16. The scarcity of oxygen in the gases of fumaroles may possibly arise from the formation of the oxides which precede the chlorides.

17. Lavas give a continuous spectrum, although covered with smoke, when looked at with Hoffmann's spectroscope with direct vision.

18. The smoke gives positive electricity, and the falling ashes negative electricity.

REFERENCE TO THE PLATES.

PLATE

Ia. The Cone of Vesuvius, in 1870, from a Photograph taken near the Observatory.

a. The Atria del Cavallo. b b. Fossa della Vetrana. c. Punta del Crocella. d. Lava of 1858 and 1867. e. Police Barrack near the Observatory. f. Part of Monte Somma.

IIa. Profile of Vesuvius, taken from a Photograph of the Observatory in the month of September, 1871.

1. The Cone, on the 13th January, 1871. 2, 2. Lava of 1871.

IIIa. Profile of Vesuvius on the 16th April, 1872, about ten days before the last Conflagration.

IVa. Vesuvius, on the 26th April, 1872, from a Photograph taken in the neighbourhood of Naples.

1. The Observatory. 2. Fossa della Vetrana. 3. Eruption of Smoke and Ashes, with Stones, from the surface of the Lava. 4. The Novelle, St. Sebastiano, and Massa. 5. Lava which took the direction of Resina. 6. Lava which, from the Crater, took the direction of the Camaldoli. 7. The Grain Stores, near Naples. 8. Resina. 9. Torre del Greco. 10. The Camaldoli.

Va. Profile of Vesuvius after the Eruption of the 26th April, 1872, from a Photograph taken near the Observatory.

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.

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."

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.

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.

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.

COTUNUITE, chloride of lead, in white, lustrous, acicular crystals, of the trimetric system, easily scratched, Sp. gr., 5·238.