' TRANSACTIONS OF SECTION ©. 499 
MONDAY, SEPTEMBER 24. 
The following Reports and Papers were read :— 
1. Ninth Report on the Circulation of the Underground Waters in the Per- 
meable Formations of England, and the Quality and Quantity of the 
Waters supplied to Various Towns and Districts from these Formations.— 
See Reports, p. 147. 
2. Report on the Harthquake Phenomena of Japan.—See Reports, p. 211. 
3. Preliminary Notice of the Earthquake of 1881 in the Island of Ischia. 
By H. J. Jounston-Uavis, F.G.S. 
The earthquake of March 4, 1881, occurred at 1.5 p.at., and resulted in the 
entire destruction of the greater part of Casamenella, severely injuring the upper 
parts of Casamicciola and Lacco-Ameno, besides Casamonte, Penella, and Fango. 
Beyond this extended an area, including a little of Porto d’ Ischia, Faiano, 
Fontana, Monterone di Forio and most of Lacco, in which the houses were fissured. 
It will thus be seen that the area affected by the shock was a remarkably small one. 
The buildings of Casamenella which were in the mesoseismal area were characterised 
by the collapse of the roofs and floors with comparatively little injury to the walls, 
showing their nearness to the seismic vertical. Passing outwards in a radial 
manner from the seismic vertical, we tind the angle of emergence rapidly declines, 
and the damage of the houses similarly diminishes, so that within a very short 
distance the effects are hardly visible. 
We may therefore conclude from these facts that we have a slight earthquake 
haying its origin very near the surface, and that its destructivenéss was dependent 
on the same cause, for had it been at any considerable depth it might have pro- 
duced movements of very slight intensity. It must also be mentioned that the 
peculiar style of architecture, the bad materials and workmanship, combined with 
age of most of the buildings, helped very greatly towards the ruin. 
It will be seen that the isoseismals assume ellipsoidal figures, with their major 
axis running nearly east and west, and are, therefore, no doubt, derived from a 
fissure whose plane strikes from a few degrees east of south to a few degrees west 
of north, passing just west of Casamenella, and therefore forming the minor axis of 
the ellipsoid. It will be observed that this is not quite correct, and that the 
isoseismals are nearer the seismic vertical on the eastern side; this, therefore, would 
incline us to believe that the fissure dips slightly to the west, so that the earth- 
wayes on the east are directed beneath and away from the surface, so as to be 
absorbed and lost, whilst those on the west would be directed towards the surface. 
Another important point is that the isoseismals are nearer each other on the 
northern side; this might be explained by the axis of greatest violence exercised 
during the production and injection of the fissure not being perpendicular but 
inclined to a few degrees east of south. 
Ischia, as is well known, is an old submarine voleanic cone surmounted by a 
large crater denuded away on the southern side. Since its upheaval at successive 
periods from beneath the sea, it has given birth to a number of subaérial eruptions 
from lateral or parasitic craterets, of which Rotaro, Montagnone, Cremate of 1302, 
Crater of Molara, Grotta della Terra, Casapolita, and Zale, are the principal 
examples. Some of these have appeared in historic times, and were preceded by a 
series of violent earthquakes that from time to time drove away the inhabitants. 
. The town of Fontana occupies the centre of the great or mother crater of 
Monte Epomeo, and if we draw a radial line from that village to the Marina at 
Lacco, we shall find that the strike of the fissure causing the earthquake lies on 
this line. Now it is well known that most lateral eruptions take place from a 
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