The record-union., 1892-04-23
DISSERTATION ON 4EMBLORS.
Sergeant Barwick Gives Some Scien-
tifc Points on the Subject.
The Supposed Cause of Seismic Dis
turbances-Three Different Styles
are Said to be Fashionable.

Now that Sergeant Barwick, the local
weather manager, has satisfied the people
that he had no hand in causing the recent
seismic disturbances-and that he did not
even predict them-he feels that he is at
liberty to say something on the subject of
earthquakes in general, consequently
when a RECoRD-UNIoN reporter APP
preached him yesterday he grew quite
communicative.
Earthquakes" said the Sergeant, "are
supposed to be the result of vibration or
conclusion produced within the earth by
some explosive force. 1t must originate
in comparatively small area, and the
chief force of the explosion must expend
itself in that area. The area disturbed
may be one of a series of cavities having
great linear extension or it may be part
of large district of any form, in which
are numerous cavities or spaces more or
less isolated. The explosion may be sin
gle or 1t may be repeated many times. 1t
may be very sudden and rapid and of
extreme violence or it may be less rapid,
and the force produced may tend more
toward upheaval than fracture. The
forces, however, must act in way not
unlike that OF gunpowder exploded in a
mine or steam bursting boiler, and the
comparisons drawn from such instances
are found to be both suggestive and eX-
planatory.
Three STYLES OF SHAKES.
"Where they are felt at the earth's sur
face, earthquakes are of three kinds, un-
dulatory, perpendicular and horizontal" !"
continued the Sergeant. 1.-THE latter fire.
quently appears to be rotary, or vorticose
(circular). The undulatory are the most
common and the least mischievous. The
perpendicular are much more rare and
far more destructive. The rotary quakes
are altogether exceptional, but when they
occur in the neighborhood of towns they
are more destructive. The undulatory
are mere undulations, heaving the ground
at any one place upward and sinking it
downward, and producing the same, or
nearly the same, results at a vast number
OF places along a certain definite course
on the earth's surface. The second per
pendicular) resembles the explosion of a
mine. They consist of sudden up
heaval "a thrust upward), but with no
undulation. The third (horizontaD are
complicated, including direct and sud
den upheaval, with an advancing wave
and this complication produces a mixed
motion, like that of steamer advancing
through cross sea.
Seismic ACCOMPLISHMENTS.
Earthquakes are sometimes preceded
or accompanied by peculiar state of the
air and weather, by rolling, detonating
and other noises, and by marked electri-
cal phenomena. But these cannot be re-
garded as essential or necessary, though
the observations that include careful
records Of all these matters are both in
teresting and valuable. The kind of
noise that occurs is different in different
places. Sometimes it is a rolling, rum
fl,o,
loaded wagons over hard road; some
times 1t is like the blinking of chains;
sometimes 1t resembles thunder close at
hand, and now and then it has been de-
scribed as clear and ringing, as if obsi-
dean or other vitrihed masses clashed
together, or were shattered in subterra-
mean cavities. The imagination is so apt
to eXaggerate sounds of this kind, and to
discover fanciful resemblances that have
little foundation in fact, that we can
hardly accept all these descriptions.
Under any circumstances, however, there
is evidence OF alienation of activity and
repose. both when we consider the earth
quake shocks
IN SPECIAL LOCALITIES,
And over the whole of very large area,
including several bands of earthquake 9
activity. On the whole, also, it seems
that when the intervals of repose are
shortest there are fewer earthquakes of
the first-class (undulatory). In refer
ence to this question it is worthy of no.
tice that in each century for many centu-
ries past there have been two periods of
chief earthquake intensity, one greater
than the other, occurring about the
middle of each century from the tiftieth
to the sixtieth year., and the other to-
wards the end of each.
''In the present century it is needless
to remind you of the great extent of
earthquake disturbance between the
years 1859 and 1869. 1t is probably be-
| lieyed by some scientists that the cycle
of increased interval disruption has again
arrived and will remain with us for from
eight to ten years, during which time
earthquake shocks wall be reported from
divers portions of the world.
"It appears as though the Pacific Coast
was getting in on time so as to give the
other portions of the world time to come
in and make a record for themselves dur
! ing the next eight or ten years.
'It must not be understood, though,
| that this country will be constantly
| shaken up for the next eight or ten years,
| but simply statistical history for thou
sands of years back show us that in the
middle ana near the end of a century
! convulsions OF nature takes place more
I tIxys