San Antonio daily light. [volume] (San Antonio, Tex.) 1886-1907, 1892-02-02
The Standard OF Length.

Brooklyn Times.
Prof. Michaelson, of Clark Universe
ty, to whom has been assigned
the determination of the physical
constant of length, Is one of the most
accurate of physicists tor the reason
that he is without mercy In the criti.
cism of his own methods and process
SEES. Rigid toward himself, ne Is
equally unbending toward others,
aud it results that while his labora-
tory is purgatory to the students the
discoveries there made are from the
start almost beyond challenging.
The absence of standard length Is
a want grievOuslyl felt both in
physical experiments and in the
practical concerns of life on which
the labors OF the student in the labor.
atory bear 80 distinctly. There are
two in common use which serve all
ends where refined precision is not
desideratum, and it is highly improb-
able that the establishment of q con-
slant will in any way affect the pop
ular use of the foot and the meter.
The labor-saving desire of the fu-
ture may indeed succeed In relegat-
ing the clumsy scale of inches, feet,
yards, perches and poles to the realm
of useless lumber where the cubit,
the barleycor the nail, the ell al
ready are and whittier the furlong is
fast going. Convenience may be
served by the decimal scale of the
French which has already been Off
cialIy adopted by this Government,
but the meter as an aliquot part of the
quadrant of the eartn's circumference
is no more accurate than the fUot as q
lasting record of the impression OF
the kings own foot in some elastic
materisl-mud, for instance. In
either case the objection to the stan
dard yard or standard meter is its
dependence on the safe preservation
of particular metallic bar which
could never be replaced if once lost.
In fact, the yard exists as three
different copies of lost original, and
speculation which of the three is to be
held standard. The original of the
standard meter is still in existence,
but if it were to vanish 1t could never
be determined again according to the
method by which it was first discov-
cred.
Three methods of determining this
physical constant have been examir I.
ed. The first rests upon the earth and
involves the measurement of great
circle and it's subdivision into equal
and convenient portions. The meter
was thus attained, but later examina-
ton of the problem has shown fatal
errors of operations on the part of the
French geodesists. At the same time
there exist two grave objections, one
being the present ignorance of the
true shape of the earth, the other
being the fact that as the earth is yet
plastic its figure, even If accurately
determined, is subject to alienation.
The second method also rests upon
the earth and involves the swing of
the pendulum. Here also accuracy is
rendered impossible Of attainment by
the same causes which remove great
circle subdivision from the solution of
the problem.
Prof. Michaelson discards the earth
entirely as hopelessly inaccurate. and
looks for q cosmical standard which
may be assumed as unchanging. For
this purpose he viii measure Z
wave length Of light at q given line
| in the spectrum and refer all measur-
es to this standard. The idea is that
this wave length can always be re-
measured and therefore the perma-
nency of the standard will be assur-
! ed.
A IL II.