1864. | Matter on Earthquakes. 57 
which permanent geologic elevations of the land are produced,” though 
too often confounded with these in all sorts of geological “ systems,” 
and ew cathedraé utterances. Nor is it “the reaction of the interior of 
a planet upon its exterior,” for that, oracular as it sounded from the 
lips of a Humboldt, is, in fact, to say nothing. 
What, then, 7s an Earthquake ? It is the transit of a wave or waves 
of elastic compression in any direction, from vertically upwards to horizon- 
tally in any azimuth, through the substance and surface of the arth, 
from any centre of impulse, or from more than one ; and which may be 
attended with sound and tidal waves, dependent upon the impulse, and 
upon circumstances of position as to sea and land. 
To understand the definition we must have a clear notion of what 
a wave is. We will return to that true threshold of Seismology, but 
first let us take a very brief glance at the history of our subject. This 
is twofold: that of the facts, or reputed facts, as found in innumerable 
EKarthquake narratives, and that of human opinion, from the dawn of 
knowledge downwards, as to these, in referring them to causes. 
The supposed first cradle of our race, or at least of that great 
branch of it from which we ourselves, and almost all our knowledge, 
have come, was situated in regions that during all history, as now, have 
been greatly disturbed by Earthquakes, which thus very early engaged 
the minds of the more observant of men. Nothing, not even thunder 
and lightning, amongst natural phenomena can have so impressed the 
imagination of early peoples, as did these suddenly felt shakings, by a 
terrible and unknown power inhabiting the unseen depths of the 
Earth, nor more imperatively stimulated to the discovery of some 
cause for them. 
The genius of the old nations of the East, that always “sought 
after a sign,” or for a final cause, was and is satisfied with a myth. 
When Brahma turned sides, there was an Earthquake, or when the 
Tortoise, on which the world rests, stirred his flippers, there was 
the like result ; and this sort travelled westwards, moulding the earlier 
than Homeric Mythology of the days when Greece was young, and 
showing itself in the mysterious power of the Trident of Neptune, 
Leioiydovos evvoriyaios. But the Greeks “desired wisdom,” and only 
missed it as to deciphering nature, because they started from arche- 
type creations of the mind, and not from inductive observation. 
There was plenty of such philosophizing on Earthquakes amongst 
them. There were three theories before the days of Aristotle: that 
of Anaximenes, the Milesian; of Anaxagoras of Klasomene; and of 
Democritus of Abdera, in order of time. Aristotle himself wrote 
largely and learnedly in the books regs Merewgoroyinwy, and regi Koowov. 
He had remarked and classified, with his accustomed comprehensive- 
ness, the different sorts of shocks by their sensible effects, dividing all 
into, érixAivrai, which strike the earth’s surface at an acute angle; Boa- 
orat, those that come right up (vertically), and sink down again, like 
a boiling spring or pot ; yacuarias, those that leave hollows after their 
departure ; {4xrai, those which break forth with eruption of wind, 
stones, mud, &e. Those which with one great push overturn everything 
are woras, and those, that with much shaking to and fro, and up and 
