The isoseismal lines as drawn by Dr. Johnston-Lavis are represented by the curves in Fig. 15. The isoseismal marked 1 bounds the area of complete destruction; it is about 1 mile long from east to west, 2/3 of a mile broad, and contains an area of not more than half a square mile. The next isoseismal (2) marks the area of partial, but still serious, destruction; this is nearly 2 miles long from east to west, 1-1/4 miles broad, and 2 square miles in area. Within the isoseismal 3, buildings were more or less slightly damaged. The course of this curve is somewhat doubtful, but, as drawn, it is about 3 miles long, 2 miles wide, and 5 square miles in area. [Illustration: FIG. 15.--Isoseismal lines of the Ischian earthquake of 1881. (_Johnston-Lavis._)] Outside the last curve, the shock diminished rapidly in intensity. At Monte Tabor and Bagno, it was very slight; in the town of Ischia, only about half the people were conscious of any movement; and at Capella, a small village to the south, it was not felt at all. Again, the shock was perceptible, though only faintly, in the neighbourhood of Campagnano, at Serrara to the south of Epomeo, and at Panza near the south-west corner of the island. On the other hand, at Fontana, which occupies approximately the centre of the crater of Epomeo, there were evidences of a distinctly stronger shock. No house actually fell, and side walls were but little injured; but the roofs, which are of great weight, suffered considerable injury. In the adjacent island of Procida, the shock was felt distinctly by many people, and by some, though slightly, at Monte di Procida, Misenum, and Bacoli, on the coast of Italy. No record whatever was given by the seismographs in the university of Naples and the observatory on Vesuvius. We have of course no means of estimating the exact size of the disturbed area, but in this respect, disastrous as the earthquake was in the neighbourhood of Casamicciola, it was clearly inferior to all but the very weakest earthquakes felt in the British Islands. POSITION OF THE EPICENTRE. In determining the position of the epicentre, Mallet's method was closely followed. Fissures in buildings were used for the most part, in two out of every three cases; and occasional measurements were made from objects overthrown, projected, or shifted, and also from the personal experiences of observers. The attempt to apply the method was, however, fraught with difficulties. The heterogeneous structure of the island was no doubt responsible for many divergent azimuths; the irregularity of the buildings both in form and material and their variety of site furnished other sources of error; even the smallness of the area was a disadvantage in lessening the number of trustworthy records.