editerranean basin.

It is not my intention here to offer any criticism as to the
construction or performances of this instrument, the rather as I must
confess I do not quite share the high opinion of its inventor as to the
certainty or exactitude of its indications.

There can be no question as to the extreme importance to science of the
establishment and continued use of a seismographic instrument of
unexceptionable construction at the Observatory upon Vesuvius; and it
would be a valuable gift to science, were the Italian Government to
enable Signor Palmieri to establish such an one. Its great value and the
very first problem to set the instrument to solve should be, by _a rigid
determination of the direction of propagation of the wave of shock_, of
those slight or stronger pulsations which precede or accompany the
Vesuvian like all other eruptions, on arriving at the Observatory, _to
fix the depth, and the position vertically beneath the cone, whence
these pulses are derived_. This would be, in fact, to fix the depth and
position beneath the mountain at which the volcanic focus is situated
for the time, or, at least, where the volcanic activity is at the time
greatest. And the assured knowledge, even within moderate limits of
accuracy, of this depth, and even for this single mountain, would be an
immense accession to our positive knowledge, and a really new stage
gained for future advances. At present, we know but little as to the
actual depth below our globe's surface at which volcanic activity
occurs, or to which it is limited, either upwards or downwards. I have,
myself, established some data upon the flanks of Etna, not yet
published, which may enable me to afford some information on the subject
hereafter. Meanwhile, Professor Palmieri possesses unrivalled
opportunities for such observations; and I trust health, life and means
may be afforded him, to become the first who shall have made this great
addition to our positive knowledge of Vulcanology.

So far, popularly at least, the alleged chief uses and value of these
seismographic instruments, at the Observatory of Vesuvius, have been
made to depend upon their being presumed to afford means for foretelling
eruptions, or affording precursory warnings of their probable progress
and destructive course.

I feel compelled to express my own total disbelief in the possibility of
any such predictions in the present state of science, by the help of any
instruments wha