our accessions of knowledge primarily upon a
different standard to his--in our talk of discovery, our posterity, in a
century or two hence, may not improbably possess the advantage of being
able, in some degree, to predict their Earthquakes. I fear the
inducement will go but a small way with the utilitarian generation,
whose bent tends much towards asking, "What has posterity ever done for
them?"

But though we cannot as yet predict the time when an Earthquake may take
place in any locality, we can, on mixed statistic and dynamic grounds,
in many cases state the limits of probable violence of the next that may
recur. For example, the three shafts of marble columns of the Temple of
Serapis, at Pozzuoli, each of about 41-1/2 feet in height, and 4 feet 10
inches in diameter at the base, remain standing alone, since they were
uncovered, in the year 1750.

Now, as we can calculate exactly what velocity of earthquake-wave motion
would be required to overset these, we are certain that, during the last
one hundred and twenty-two years, the site of the Temple, and we may
say Naples and the Phlegraean fields generally, have never experienced a
shock as great as the very moderate one that would overset these
columns. A shock whose wave particle had a horizontal velocity of only
about 3-1/2 feet (British) per second would overturn these columns;
which is only about one-fourth the velocity (within the meizoseismic
area) of the great shock of 1857, that produced wide-spread destruction
in the Basilicatas, and not enough to throw down any reasonably
well-built house of moderate height.

Naples, so far as Earthquake is concerned, whether coming from the
throes of Vesuvius or elsewhere, has a pretty good chance of safety. She
may possibly (though not probably) be some day smothered in ashes; but
is in little danger of being shaken to the earth. During this time there
have been taking place, larger eruptions of Vesuvius and earthquake
shocks from other centres, together probably about the same number of
times as the numbers of those years, when those columns have been more
or less shaken.

We may therefore affirm that the probability (on the basis of this
experience _only_) is, say 120 to 1, that the next shock, whether
derived from Vesuvius, or elsewhere, that may shake Pozzuoli, will be
one less in power than would be needed to overturn the shafts of the
Temple of Serapis there.

* * * * *

Let us