parts of
our globe, we should probably find scarcely a day pass without a very
sensible Earthquake occurring somewhere, whilst, as regards still
smaller tremors, it might almost be said that our globe, as a whole, is
scarcely ever free from them.

As respects the distribution of seismic energy in space of our earth's
surface, it is that of bands of variable and of great breadth, with
sensible seismic influence extending to from 5 deg. to 15 deg.
transversely, which very generally follow:

1. The lines of elevated tracts which mark and divide the great
oceanic or terra-oceanic basins (or _saucers_, as I have called
them, from their shallowness in relation to surface, in this
discussion) of the earth's surface.

2. And in so far as these are frequently the lines of mountain
chains, and these latter those of volcanic vents, so the
seismic bands are found to follow these likewise. Isolated
Volcanoes are found in these bands also.

3. While sensible seismic influence is generally limited to
the average width of the band, paroxysmal efforts are
occasionally propagated to great distances transversely beyond
that.

4. The sensible width of the band depends upon the energy
developed at each point of the length, and upon the accidental
geologic and topographic conditions along the same.

5. Seismic energy _may_ become sensible at any point of the
earth's surface, its efforts being, however, greater and more
frequent as the great lines of elevation and of volcanic
activity are approached; yet not in the inverse ratio of
distance, for many of the most frequently and terribly shaken
regions of the earth, as the east shore of the Adriatic, Syria,
Asia Minor, Northern India, etc., are at great distances from
active Volcanoes.

6. The surfaces of minimum or of no known disturbance are the
central areas of great oceanic or of terra-oceanic basins or
saucers, and the greater islands existing in shallow seas.

Space obliges me to pass unnoticed here many minor but not unimportant
deductions. The discussions as to distribution in time and space occupy
seventy-two pages of this fourth and last Report, the remainder of which
(thirty-one pages) embraces the description and mathematical discussion
as to seismometers, to which I may refer, as comprising the most
complete account of these instruments that