"معاملات الجمعية الجغرافية في بومباي. من يناير ١٨٦٣ حتى ديسمبر ١٨٦٤. (تحرير السكرتير.) المجلد XVII." [‎٢‎٩‎٠] (٥٢٤/٤٦٧)

290 NOTES ON THE EARTHQUAKE
Here in the East, among the old nations, observations made by the
inhabitants when noticed usually proclaim that on such an occasion
Bruhma turned sides, or that the world-bearing i ortoise had stirred
his flippers, or, as related by a correspondent in Kattyawar relative to
the earthquake forming the subject of this paper, that the iniquity
of the people had become so great and intolerable, that as a warning
mother earth had signified her displeasure by an ominous quake.
In a late number of a London Scientific Journal, already referred to,
the question has been asked, “ What is an Earthquake ? There are some
who have read, many who have talked of them, and some even who
have felt their effects. But what are these effects ? and the cause—
what is it ? Let us mention one or two things which an Earthquake is
not. It is never one of the means by which permanent geologic eleva
tions of the land are produced, though too often confounded with these
in all sorts of geological systems and ex cathedra 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, is an earthquake ? Mr. Mallet here gives us
the definition of science of to-day as the result of his searching analysis
of the subject, contained in the Beport of the British Association for
1858.
“ An earthquake,” he says, “ is the transit of a wave or waves of elas
tic compression in any direction from vertically upwards to horizontally
in any azimuth, through the substance and surface of the earth, from
any centre of impulse, or from more than one; and which may be at
tended with sound and tidal waves, dependant upon the impulse and
circumstances of position as to sea and land.” This is what science
defines an earthquake to be, but which, to receive with intelligence,
had better be investigated before we proceed further, and here we may
in a concise manner do this in the words of the Seismologist already
mentioned:—
“The earthquake shock is produced by a wave of elastic com
pression passing through some portion of the substance of our earth.
Elasticity is that property in the matter which tends to the restoration
of figures in solids, and of volume in liquids and gases when altered
by an extraneous force, and is a term often confounded with another-—
flexibility. Thus, when people praise the springs of an easy going