<1 As it is known, the eddying earthquake is nothing more than an -effect or a result of two movements,
which take place in two directions diverse to each other. The narration, agreeing with this particular fact,
once more demonstrates the truth discovered by science, that is, that the phenomenon of the earthquake
consists of many shocks which take place in directions angular to each other. It is understood therefore, that
the buildings put into violent movement in a certain direction and then forced to change this movement suddenly,
must rotate on themselves and for this reason, suffer grave damage.
€| But alas! the single circumstance of the variation of direction could not explain so much ruin, or to speak
more exactly a ruin so complete as it was unfortunately in reality. Arguing thus from certain particular
phenomena, we come to the final conclusion that the intensity of the Calabro-Sicilian earthquake would not
have been so excessive as to justify a work of destruction so complete and so general, if other grievous coefficients
had not unluckily intervened, chief of these being the wretched construction of the buildings. In the
walls, rounded stones mortered with poor lime prevailed, and what is more, in buildings of three or four
stories, this would have occasioned considerable damage in such walls and buildings even in an earthquake
of minor intensity. Imagine therefore what it must have been in an earthquake such as that of December 28"'!
t | But you must not think that my saying so contradicts my affirmation that the intensity of the earthquake
was most intensely excessive. If the same shocks had taken place, for example, in regions where the houses
were better built, we should certainly have had to lament many victims; not so many however as we must
to-day deplore, because, let us well remember, the earthquake, itself, kills no-one; it is, rather, its disastrous
effects which kill.
<1 Let us hope, therefore that, if they must rebuild all from the beginning, they will take once for ever
such precautions as science and conscience demand, since a long time but in vain.
<1 Another important co-efficient of grievous damage, in fact incalculable, of which the observers of the
present publication will be able to find traces, was certainly the seaquake, which swept away, both on the
Calabrian coast and on the Sicilian, but more on the latter, whole groups of houses situated on the shore,
indeed, entire villages! It would be of the highest importance to examine the manner of production of the
seaquake; but on this problem, which only interests science, the reader, if he will, can find elsewhere, profound
studies and observations.
C| Here are only described artistically the disasterous effects of the phenomenon, more terrible and eloquent
than any words in their dumb simplicity.
I deem necessary, however, a word of explanation on some points of the present publication; points which
have a purely scientific side, and these are for the map of the isoseismics (lines of equal intensity in an
earthquake) and for the charts traced by the seismic instruments in all the world.
if I shall begin with the isoseismics, and, in order to explain more clearly, I shall seek the aid of a
comparison.
CJ We know by ordinary experience that, sound, light, and indeed all phenomena which go under the name
of vibratory phenomena in physics, weaken in their effect the further they are removed from their source,
or point of origin; and so it happens with an earthquake, which consists precisely in a vibratory phenomenon
and which is thus included in the common law.
€[ Its intensity weakens in proportion as it is removed from its point of origin, called epicentric; the epi-
centric zone or area is precisely that in which the effects are gravest and most felt, as is shown by those
observed in the regions situated around.
To obtain a result such as the scientific determination of the epicentric area, a kind of index has for
many years been prepared, which contains in short paragraphs the description of the usual effects happening
during an earthquake of a given intensity; in this way, even without seismographic instruments, and
without special calculations, the approximate intensity of a given earthquake can be sufficiently well estimated.
•I This index is commonly called the Seismic Scale and the scale generally adopted to day and which