II4 CHARLES DAVISON 
which are still standing, and the continuous lines the boundaries 
of the areas within which buildings suffered marked damage by the 
earthquakes of 1796, 1828, 1881, and 1883. It will be noticed 
that these areas show a progressive increase in size. The broken 
line, slightly curved, shows the position of the radial fracture 
with which the earthquakes were probably connected; and it is 
important to notice that the chief damage wrought by the earth- 
quakes of 1881 and 1883 was concentrated along this line near 
Casamicciola. . 
These earthquakes were studied in great detail by the late 
Dr. H. J. Johnston-Lavis. The isoseismal bounding the area of 
complete destruction in 1881 includes only } square mile, the area 
of partial though serious destruction about 2 square miles, and 
that within which buildings were slightly damaged about 5 squate 
miles. Still farther, the shock continued to diminish rapidly in 
intensity. It was felt in the neighboring island of Procida, and 
by some persons, though very slightly, on the Italian coast, the 
total area being probably less than 300 square miles. From the 
inclination of the fissures made in buildings, Dr. Johnston-Lavis 
estimated the mean depth of the focus at about 3 mile. The 
earthquake was followed by a few slight after-shocks on March 7 
(2 shocks), 11-12, 15-16, 17-18, and 27(?), April 5 and 6, and - 
July 18. 
The earthquake of July 28, 1883, was much stronger, and 
resulted in great loss of life at Casamicciola. It was preceded at 
that place by a‘slight shock on July 24, and by an earth-sound a 
quarter of an hour beforehand. The areas of complete, partial 
destruction and slight damage were respectively 3, 11, and 30 
square miles. In this earthquake, also, the intensity diminished 
very rapidly outward. The shock was felt in Italy near the coast 
and by a few persons in Naples, which is 20 miles from Casa- 
micciola. The disturbed area can hardly therefore have contained . 
more than 1,250 square miles. The mean depth of the focus 
was again found to be about 3 mile. The shock was remarkable 
for the entire absence of preliminary sound or tremor and for its 
great initial strength, a great part of the ruin being caused during 
the first few seconds. Between July 28 and August 3, 21 slight 
