5. JOHNSTON-LAVIS, H.J.--_Monograph of the Earthquakes of Ischia_ (1885). 6. MERCALLI, G.--_Vulcani e fenomeni vulcanici in Italia_ (vol. iii. of _Geologia d'Italia_, by G. Negri, A. Stoppani, and G. Mercalli), 1883, pp. 46-50, 331-332. 7. ---- _L'Isola d'Ischia ed il terremoto del 28 luglio 1883_ (Milano, 1884). 8. PALMIERI, L., E A. OGLIALORO.--"Sul terremoto dell' Isola d'Ischia della sera del 28 luglio 1883." Napoli, _R. Accad. Atti_, vol. i., 1884, pp. 1-28. 9. ROSSI, M.S. DE.--"Il terremoto di Casamicciola del 4 marzo 1881." _Bull. del Vulc. Ital._, anno viii., 1881, pp. 5-12. (In the same volume are brief notices by different writers on pp. 22, 38-42, 52-53, 67-68, 70-74.) 10. ---- "Raccolta di fatti, relazioni, bibliografie sul terremoto di Casamicciola del 28 luglio 1883, con brevi osservazioni." _Bull. del Vulc. Ital._, anno xi., 1884, pp. 65-172. 11. ---- "Intorno all' odierna fase dei terremoti in Italia e segnatamente sul terremoto in Casamicciola del 4 Marzo 1881." _Ital. Soc. Geogr. Boll._, 1881. 12. SERPIERI, A.--"Sul terremoto d'Ischia il 28 luglio 1883." _Scritti di Sismologia_, Pte. ii., pp. 207-216. 13. ---- "Sul terremoto dell' Isola d'Ischia il 28 luglio 1883." _Ibid._, pp. 217-232. FOOTNOTES: [21] The shaded areas indicate the principal trachytic masses, the broken lines represent the boundaries of the craters that are still recognisable, and the dotted lines the boundaries of the areas within which buildings were damaged by the earthquakes of 1796, 1828, 1881, and 1883 (according to Mercalli). The continuous curved line shows the position of the radial fracture with which the earthquakes were probably connected. The trachytic masses and craters are denoted by the following tables:-- _a._ Epomeo. _b._ Trippiti. _c._ Vetta. _d._ Garofoli. _e._ Vatoliere. _f._ Campagnano. _g._ Vezza. _h._ Imperatore. _i._ C. St. Angelo. _j._ Lo Toppo. _k._ Marecocco. _l._ Zale. _m._ Rotaro. _n._ Montagnone. _p._ Bagno. _q._ Tabor. _r._ P. Castiglione. _s._ Cremate. _t._ Arso. _u._ Porto d'Ischia. [22] It is possible that Monte Campagnano may form an exception to this statement. [23] Shocks were felt in the island in 1559 and 1659, but one at least was of external origin. [24] Prof. Mercalli, from the five estimates of the angle of emergence which he considered most reliable, found the mean depth to be about 3,280 feet. [25] Professor de Rossi estimated the mean duration as not much exceeding ten seconds. Dr. Johnston-Lavis, on the other hand, considers the general estimate of fifteen seconds as far too low. In one case, at Casamicciola, he ranks it as high as thirty-one seconds. [26] Quoted from the useful translation of Covelli's memoir given by Dr. Johnston-Lavis.