§5. THE PHLEGR^AN FIELDS AND LIPARI ISLES. 811 



pure, in the state of a white earthy powder, are in the 

 highest degree interesting.* 



The earthquakes of 1538, which were followed by an 

 eruption of mud, pumice-stone, and ashes, that burst forth 

 from a gulf near the town of Tripergola and formed the 

 volcanic mound called Monte Nuovo, and by the permanent 

 elevation of the coast to beyond Puzzuoli, were mentioned 

 in a former Lecture {ante, p. 109). f 



The Lipari Isles, between Naples and Sicily, lying, as it 

 were, midway between Vesuvius and Etna, present a cha- 

 racter very analogous to the district above described. The 

 crater of one of the islands, Stromboli, has been in constant 

 activity from the earliest historical period. It always con- 

 tains melted lava in constant motion, and at uncertain 

 intervals the molten mass suddenly rises, and large bubbles 

 appear, which, upon reaching to the brim of the crater, 

 explode with a sound resembling thunder, and masses of 

 lava, with dust and smoke, are thrown into the air ; the in- 

 candescent fluid then sinks down to its former level. J 



The Cliffs of St. Calogero, which are about two hundred 

 feet high, and extend four or five miles along the coast, 

 consist of horizontal beds of volcanic tuff. From the peren- 

 nial emanation of sulphurous vapours, the rocks are decom- 

 posed ; alum, gypsum, and other sulphuric salts, are formed, 

 as well as muriate of ammonia, and silky crystals of boracic 

 acid. The dark clays have become yellow, white, red, 

 pink, &c. and marked with stripes of various colours, from 

 the gaseous emanations that are constantly issuing from 

 beneath : these mottled clays strikingly resemble in appear - 



* Geol. Trans, vol. ii. p. 345. See also, ante, p. 77, and Sir H. Davy's 

 remarks on the Lake of the Solfatara, in the Appendix to vol. i. p. 452. 



f A letter on the formation of Monte Nuovo, by an eye-witness, is 

 still extant : a translation of it, by Mr. Leonard Horner, is published 

 in the Quarterly Journal of the Geological Society of London, No. 9, 

 p. 19. 



% Spallanzani. 



