The San Francisco call., 1910-04-05
CEIJcNOORAPH A |
WAVE RECORDER |
Scientist Describes Method
Of Tracing Quakes Of
Earth on Paper
Written for The Call by
REV. JEROME S. RICARD. S.

from It's humble beginnings up to its
actual state of evolution has ALWAYS
been to seek steadiness in an environ
ment of unsteadiness For how could
the solid earth on which we tread and
i've be made to describe its own move
ments of whatever kind they may be,
compressions. distortions, alternate con-
densations and rarefactions such as
those of the air in the propagation of
sound or the mere travelling of crests
and troughs, as in the case of water
waves, If the describing apparatus is
not attached to steady point or mass
which human genius has been able to
snatch from the general condition of
unrest all around and does not itself
share the general movement? Or, con-
versely. if the printing point sharing
in the general movement, the paper on
which 1T writes is not somehow or
other held in the state of rest.
Whether we consult the Japanese
school of seismography or the British
or the entirely independent italian
school, we find the same dominating
idea-a steady point in the midst of
general unsteadiness. The latest ad-
vance. however, that has been made
and which will mark the beginning of
new era for seismography, is con-
tanned in the rather paradoxical propo-
sltion-have the steady point itself as
unsteady as possible within assigned
limits. Under a proper arrangement
baf int NTH
impulse of a seismic wave and print
most accurate autograph But the
paradox can easily be explained.
EXPLANATION OF PARADOX
Suppose a perfect sphere is at rest
on a perfect plane within confining
ring at a convenient distance from its
equatorial belt to keep it from stray
ing away too far. Manifestly there
will be an extreme degree of unsteadi-
ness, because the least disturbing force
will set the sphere a-rolling. If more
over, other things remaining equal, the
sphere is very heavy in relation to
everything else round about, it will
possess high degree of relative steadi-
ness because its great inertia will tend
to hold it in -statu quo.
rod may be conceived to shoot forth
from the sphere at some convenient
spot, and a system of weightless null
tiplying levers be attached. to the pro-
jecting end.
Thirdly, the last little stick of the
lever system may be- furnished with
a weightless printing point, under
which revolving drum exposes an
ever new space to write upon. Such
in short is the skeleton idea of the
seismograph in it's most novel con-
ception. But in this ideal picture there
is one serious defect to be removed
and few gaps to be filled in When
the solid wave arrives and gets
through the plane on which the sphere |
stands the latter's point of support |
will be shifted from under it and it
will appear to fall against the re-
straining ring in a direction opposite |
to that of the wave, whence, as most
unsteady, it will rebound over to the
opposite side very much as the billiard
ball does on the billiard table This
rolling and oscillating would evil |
IDENTIFY be fatal to the recording sys-
tenn and the record, if any al all, were
valueless.
PERFECT SPHERE UNMANAGEABLE
So the perfect sphere is to be set
aside as unmanageable, and likewise |
the frictionless plane for its point of
To one accustomed to tumble among
the possibilities of things it might oc- |
cur to use a slender but rigid and
well ribbed rod of steel or cast iron |
of suitable length, say of three and a |
half or four feet; set it upright on |
universal motion system of delicate |
springs of the best material and the |
finest tempering and then load it's top |
with heavy. large clock weights as far |
as consistent with the slender and |
most flexible Cardan suspension at the |
foot
Such contrivance might be deemed |
as fair an equivalent as human inge- |
nuity could we'll devise; its unsteadi- |
ness is superlatively near to or even |
ideal perfection itself; 1T is so great, in |
fact, that one might stand in fear and /
trembling lest a breath of air would |
make 1t go down even as a house of |
cards. If adopted for practical pur-
poses, one thing is sure-there would |
be no end OF trouble bringing the frivo-
lous thing to state of equilibrium; the |
operator would have to summon to his |
aid the very patience of Job. if not |
trifle more Strenuous labor, however
conquers all difficulties; the feat is not
only possible, but has been accom-
plished.
The confining ring can also be dis |
pensed with and its place taken by four
stout set screws, to the effect that when
the loaded rod strays from equiIib-
rum its massive head shall not fall too
far to one side and shall fall the same
amount all around.
SIMPLE INVERTED PENDULUM
The apparatus so far described is
simply an inverted pendulum, with four |
delicate points of suspension at the
foot, two of which are conveniently
placed in the plane of the meridian
and two in that of the prime vertical /
and the four together constitute a uni
versal motion device analogous to that |
of a telescope set on an equatorial
mounting.
By this manner of suspension is the |
pendulum free to swing in any one |
plane and enabled, under a rotary i'm
pulse to describe a cone. But fresh /
difficulty arises from the fact that ALL
pendulums have not simply a tendency
to swing, but tendency to periodic |
swing which reproduces backward the |
movement impaired forward, this osciI- /
lation continuing until finally stopped I
by the force of gravity. If this tend |
ency to continue their own movement /
to and fro is not checked, 1T will GER
tainly get mixed up with the wavelike /
motion of the earth's crust, which
should be the only controlling factor
With a view then to counteract the |
pendulum's own periodic oscillation
there can be attached to its heavy bob
ar1i ipc Al