Fort Worth gazette. [volume] (Fort Worth, Tex.) 1891-1898, 1893-01-22

NNNNIUUIIL
and tertiary vibrations to such ain 81.
tent that the pulsati3ns are beyond the
reach Of analysis except In the most gen
eral terms. The vibration produced f,v
q rapidly moving locomotive is verita-
bic but miniature earthquake. the Quick
spasm felt when the Quafrymau "nuts
on 9 shot by which perhaps balanced
blocks OF stone are sci 10 rocking or even
overturned, differs only In decree ana
not at all In kind from tho great fremcr
that wrecks cities; the artificial expIo.
sion at Flood Rock, New YORK. harbas
q few years ago. developed n coneiderai
bic earthquake whose vibrations wore
recorded by seismometers scores Of miles
away in different directions and within
lew months damaging eorthauake
extensively recorded in the duly press
WIS rev hours later traced to the ex-
plosion Of powder house.
For aforementioned centuries earth.
guakes were simply feared as the most
dreadful scourge Of mankind: for a few
centuries they Wrre recorded and studied
IN dcsultory fashion through the bavoe
they had wrought for few decades tbev
have been Investigated IA more systematic
iashlon' and q variety Of apparatus has
bceh ueAlseu Tor measuring the trcmors OF
winch they consist The simplest appara-
tn3 is the scismCsc0pp. of which there
are many patterns. an based on The
principle Of inertil IN virtue Of which
bodies resting M IN and not connected
with the earth tend to remain stationary
rather than partake Of sudden move.
inents Of the earth mass A primitive
form Is simply howl OF mercury rest.
ing on tablet or pillar fixed IN the earth
when the tremur comes the tablet aud
bowl are displaced with the earth while
the mercury. partially restrained by iu-
uf Nt.. ~ A..
commonly Ia such direction rs 10 lndi-
cate the course Of the vibrntiOn. Auotber
primitive form Is series of solid cylin-
dcrs Of uniform height but varying diam
eters SET upright "a 4 tablet connected
directly with the earth: when the tablet
Is shaken by the earth trcmOr the cyl
iuders. restrained by inertia. rock to and
FRO until some are overturned. the inten-
sity Of the vibration being roughly meas
urcd by the number oyerthrown and the
direction Of propagation by the position
IN which they lie The modern selsmo-
scope commonly consists Of a MSS Of
metal sometimes like clock weight
suspended in such muuner as 10 swing
freely In all directions from an arm
connected with n pillar set Ia the earth:
the earth troinOrs are communicated to
the pillar and thence 10 the arm, while
The weight. tending 10 remain STATIONARY,
spcct to pillar and arm. Sometimes the
weight Is provided with an index. or pom
ell, lightly touching "A horizontal plate be
low ia which cast the direction and am
plitudc Of the apparent swinging Of the
weight Tor nctual swinging of the pillar
and ARM are inscribed on the plate; and
another weight may be suspended by
springs In such manner as 60 indicnte the
vertical movement. which may also be In
uf4tfil. hs, Lac lass "A
This form Of apparatus rs called ses-
mometcr. Sometimes the seismometer Is
connected with clock in such manner
that tie clock Is stopped by the apparent
swing of the weight, when the apparatus
gives a single time record OF the earth
tremor Again, the clock may be provid-
ed with a slowly rotating plate 80 ar
ranged as 10 bc set In motion by the ini-
tial tremor aud fitted to receive marks
from pencils connected with the weights
in such manner that the various move
ments, both horizontal and vertical, with
the precise times Of their occurrence, are
successfully recorded; the apparatus then
being self-recOrding seismometer or scis.
mograph, aud the record being properly
called d seismoNam. Now IL ~ evident
that II the seismogram OF an earthquake
Ehocl; Is perfect II viii Indicate the exact
horizontal and vertical movements Of
/. @. practically IL win record "the path
Of the earth particle and thus give a
measure OF the velocity and amplitude
of the vibrations Indeed the three rec
tannIlar couponents -east-west, north.
south, uptown of the motion recorded
in the seismogram Of an earthquake
shock have actually been combined and
converted into n tangible representation
of the vibration by Professor Sekiya of
Japan by means Of q long wire bent into
such shape as 10 follow the pain OF
the earth particle
Whether so slight rs 10 be impercepd-
Bile to the sense and recognized only. by
the most delicate apparatus or no violent
as To overthrow cities and issure solid
earth or rock in the course OF each pas
sing undulati0n, the earthquake Is simply
an elastic vibration Ia the solid earth
propagated Ia all directions from cen
Tor Tor focal tract) at a rate Of about
three miles per second The amplitude
OF the vibrations u. G., the distance
through which n given particle OF the
earth matter vibrRtes) Is probably m
most cases only a fraction of an inch
ut depths below the surface; but as the
tiemor approaches the surface, aud par
tiCularly when II passes into houses,
monuments and other structures, ana
even into steep hills rising above the
general level, the amplitude may De
many times multiplied. Every object on
the earth's surface, each wall OF house,
each element in every artlheial structure,
has certain vibration period depending
on It's size, foru, elasticity ana other
coalitions. /. G., il is susceptible oil rhy-