Page:Great Neapolitan Earthquake of 1857.djvu/41



Seismology an older and more mature branch of science than it is, it would be impertinent to enter at any length into the means and methods by which it is to be pursued, in the observation of earthquake phenomena. Dating, however, for anything approaching to scientific guidance or precision, not more than twelve years back, it is the more necessary to make generally intelligible the methods of observation which can be pursued in a seismic region after the occurrence of the shock, in order that the evidence upon which conclusions may be drawn as to the direction, velocity, amount of movement, &c., of the latter may be accepted with their just weight; and the rather, because as yet it is not to all persons quite self-evident how any information whatever can be had or conclusions drawn as to a phenomenon so perfectly transient and momentary as an earthquake shock, by examination, at a considerable time after its occurrence, of the region over which it has passed.