4 ON THE FACTS AND THEORY OF EARTHQUAKE PHENOMENA. 71 
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nothing like one or more great general horizontal directions of seismic move- 
ment can exist upon any very large tracts of the earth’s surface ; and that if 
it be even possible to assign, as proposed by M. Perrey, a general horizontal 
component for limited areas, the method does not admit of extension. The 
normal type of an elastic wave in a homogeneous solid, is only varied, so far 
as observation yet goes, by the accidents principally of material and surface, 
whether the area of disturbance be great or small. 
Nor does the seismic intensity in any part of the world, so far as originating 
impulse is concerned, seem connected with the superficial character, to the 
greatest known depth, of the geologic formations, beyond what connexion 
is necessarily inferential from the seismic bands (where they exist) following, 
on the whole, the lines of mountains and ridges that separate the surface- 
basins of the earth, whether volcanic or not. While, therefore, the seismic 
waves diverge, from axial lines that are generally of the older rock forma- 
tions, and often of crystalline igneous rocks or actively volcanic, they pene- 
trate thence formations of every age and sort, even to plains of the most 
recent post-pleistocene clays, sands, and gravels ; and occasionally, by the 
secondary efforts of great shocks, these loose materials are shaken or caused 
to slip and gather up into new forms (as in the Ullah Bund at the mouths 
of the Indus, &c.), and so the earthquake has come to be mistakenly viewed 
as a direct agent of elevation. Its true cosmical function is the very opposite : 
it is part of the dislocating, degrading, and levelling machinery of the ser- 
face of our globe, while the part of the volcano is restoration and renewal. 
Both are, however, not creative but conservative (strange as it may sound), 
and suited to the period of man’s appearance and possession of the earth. 
Viewing as a whole, and in a single glance, the distribution of seismic 
ehergy over the whole globe, it presents (so far as we yet know) a vast loop 
or band round the Pacific, a more broken and irregular one around the 
Atlantic, with subdividing bands and a vast broad band stretching across 
Europe and Asia, and uniting them. 
Thus an apparent preponderance of seismic surface seems to lie about the 
temperate and torrid zones, both northern and southern; but extended 
observation is yet required in high latitudes, and particularly in the Autarctic 
ones, before we dare venture to affirm that there is a real preponderance 
extending over any one or more great climatic bands or zones of the earth’s 
surface. 
The following are perhaps the most general conclusions that are at pre- 
- sent justifiable :— 
- Ist. The superficial distribution of seismic influence over existing terrestrial 
space does not follow the law of distribution in historic time; it is not 
one of uniformity. There is this resemblance, which, however, is 
not a true analogy,—that as the distribution is paroxysmal in time, 
so it is local in space. 
2nd. The normal type of superficial distribution is that of bands of variable 
and of great breadth, with sensible seismic intluence extending from 
5° to 15° in width transversely. 
$rd. These bands very generally follow the lines of elevation which mark 
and divide the great oceanic or terr-oceanic basins (saucers) of the 
earth’s surface. 
_ 4th. And in so far as these are frequently the lines of mountain-chains, 
e and these latter those of voleanic vents, so the seismic bands are 
: i found to follow them likewise. 
_- 5th. Although the sensible influence is generally limited to the average 
